Troubleshooting guide

Functional Coatings

Heat-seal lacquers, barrier coatings and primers: seal initiation, coat weight, Cobb, kit, OTR, WVTR and blocking.

Uniform Industries · Greater Noida, India · ufindustries.com
Figures are typical for the class and carry their test method. The values that govern a supply are those on the Technical Data Sheet for the grade.

Before you start

How to use this guide

Work down the page. Cheap checks before expensive ones, and measure before you change anything.

Do not open a seal fault until you know the jaw temperature, dwell and pressure the machine actually delivered; a seal load quoted without all three is not a figure, it is an anecdote.
Weigh the coat before you change anything else, because most calls that begin "the coating has changed" end at a dry coat weight that has moved by 20 per cent.
Seal strength is read not less than 24 h after sealing, at 23 C and 50 % RH; a strip pulled at the machine two minutes after the jaw reads low and sends you chasing a fault that does not exist.
Barrier and seal numbers belong to a construction, never to the drum, so quote the base material, the coat weight, the method and the condition with every result and re-measure on the customer's own base before anything goes into a specification.
Change one variable, then give the line 200 m before you read it again; a coating line carries its history in the tunnel and the chill roll for longer than an operator expects.
When a grade is running at the edge of its window, change the grade and not the process, because a window you have to hold with three compensations will not survive the next shift.
Nothing goes on or into a sealing jaw until the drive is isolated and locked off and the pneumatics are bled; a jaw that cycles while a hand is in it is the one fault in this guide that cannot be re-run.

Functional CoatingsHow to use this guide

The process

What happens, in order, and the one variable held at each step.

The process

What is controlled at each step

Functional CoatingsThe process

Control variables

What to hold, and how to measure it

Variable	Target	How it is measured	How it drifts
Dry coat weight	Peelable lacquer 3 to 4 g/m2; lock seal 4 to 6; low-temperature lacquer 3 to 5; grease and water barrier 6 to 10; moisture top coat 8 to 12 in two passes; oxygen base coat 2 to 4 on film, 4 to 8 on board; heat-sealable barrier 8 to 14	Cut at least 100 cm2 from the uncoated base of the same reel and from the coated web, condition both 24 h at 23 C and 50 % RH, then weigh on a balance reading to 1 mg and average at least three pairs; report g/m2 dry at both edges and the centre. On foil or film, ash or solvent-extract the coating off a weighed piece instead, which removes the base variation entirely. A single before-and-after pair on board is an indication, not a figure, because base grammage varies by 2 to 3 per cent and on a 250 g/m2 board that is 5 to 8 g/m2, larger than the coating being weighed	Falls through a run as the cell walls load and the blade wears, and falls every time the pan is topped up with water to hold a cup reading; evaporation on its own raises solids and would raise the dry weight, so it is the correction and not the evaporation that takes the coat weight down. The operator sees it first as a seal that has gone soft or a kit rating that has dropped a point
Supply viscosity	Heat-seal lacquers 22 to 30 s; grease and water barrier 25 to 40 s; oxygen base coat 30 to 45 s; moisture top coat 25 to 35 s	ISO 2431 flow cup, 4 mm orifice, at 25 C. Draw from the pan and bring the sample to 25 C plus or minus 0.5 C before reading; or read as drawn with the pan temperature recorded beside the figure, in which case it is a trend reading and is not compared with the 25 C specification. If the plant uses a DIN 53211 cup, the so-called DIN 4, record which cup was used with the reading, because the two cups do not read the same seconds and their figures must not be compared	Climbs through a run as water leaves the open pan, and climbs at start-up when the pan is cold; a 5 C fall reads as several seconds on the cup, which is a real viscosity change caused by temperature and not a change in the coating, so correct the pan temperature rather than the coating
Solids as supplied	Heat-seal lacquers 38 to 48 % w/w; grease and water barrier 40 to 50 %; moisture top coat 38 to 45 %; oxygen base coat 12 to 18 %	ISO 3251, weighed residue after the stated oven condition; run it on the pan, not only on the drum, whenever coat weight is in question	Rises with evaporation and falls every time water is added to correct a cup reading; two or three water corrections in a shift move dry coat weight more than any anilox change
pH of the dispersion	8.0 to 9.0 for the acrylic and styrene-acrylic dispersions; the polyvinyl-alcohol oxygen base coat is not pH-stabilised and is not corrected this way	Calibrated electrode in the pan at running temperature, buffer-checked at the start of each shift; paper strips are not adequate on a dispersion	Falls through a long run as ammonia leaves the open pan, and the dispersion begins to thicken and coagulate at the blade; the symptom arrives as streaks and grit, not as a pH reading
Web temperature in the tunnel	70 to 110 C web temperature on paper, board, foil and PET; cap at 85 to 95 C web on BOPP and below about 75 C web on PE, where the film distorts before the coating is the problem. Water-based primers: 60 to 80 C air, which is not the same measurement as web temperature, so record both	Non-contact infrared thermometer on the web at the tunnel exit, emissivity set for the substrate; zone set-points on the panel are air temperature and are not the web	Falls as line speed rises and as the extraction dampers move; a coating that was dry at 200 m/min holds carrier at 280 m/min at the same set-points, and that carrier shows up 24 h later as a blocked reel
Rewind web temperature	Below 35 C at the chill roll exit, and below 30 C for UniSeal-545LT	Infrared thermometer at the chill roll exit and again on the outer wrap of the built reel; a chill roll with fouled internals reads correct on its inlet gauge and does nothing to the web	Rises quietly as chilled water temperature climbs through the afternoon; the reel goes to store warm and the blocking clock starts at a temperature nobody recorded
Substrate surface energy	38 to 42 mN/m or above for treated film work; metallised PET and BOPP checked on the reel you are about to run, not on the certificate	ISO 8296 test inks, or ASTM D2578 where the substrate is polyethylene or polypropylene film, which is that standard's scope. Applied on the reel after it is loaded, at both edges and the centre, and again after any stop of more than an hour. Check both faces of the reel to confirm which one carries the treatment before the head is set. Dyne pens are a screening tool only and typically read 2 to 4 mN/m high against the inks	Decays with age and with reel-store temperature, fastest on BOPP; treatment applied three months ago at 42 mN/m is commonly 34 to 36 mN/m by the time it reaches the coater

Functional CoatingsControl variables

Control variables

What to hold, and how to measure it

Variable	Target	How it is measured	How it drifts
Seal jaw temperature, dwell and pressure	Reference condition 0.5 s dwell at 0.2 N/mm2, one side heated, flat Teflon-faced jaws	ASTM F2029 for sample preparation. To verify the machine: with the machine in stop, the jaw drive isolated and locked off and the pneumatics bled, apply a thermal indicating strip or a surface thermocouple to the jaw face, then restore power and read the face on a single controlled closure with no hands in the jaw. Take jaw pressure with pressure-indicating film on the same single closure, not on the air-line gauge. Let the jaw cool to hand temperature and isolate electrically before stripping tape, changing cartridge heaters or re-facing	Jaw face temperature falls 10 to 25 C below the set-point as cartridge heaters age or Teflon tape builds up, and it falls unevenly, which is where a cross-web seal variation is usually born
Anilox or gravure cell volume	Quote the screen and the volume together and specify against the volume: film primers 200 to 250 l/cm at 2 to 4 cm3/m2; heat-seal lacquers at 3 to 6 g/m2 dry roughly 12 to 25 cm3/m2 (gravure 70 to 120 l/cm); barrier build at 6 to 12 g/m2 dry roughly 25 to 45 cm3/m2 deep-engraved (gravure 40 to 70 l/cm) or two passes; flexo 140 to 300 l/cm at 4 to 12 cm3/m2 with a chambered blade	Measure the roll volume in cm3/m2, by interferometry or a calibrated volume check; do not trust the engraving specification stamped on the end cap, and do not specify in l/cm alone, because two rolls at the same screen count can differ by two to one in volume on cell depth, angle and engraving type. Size the roll from the arithmetic: wet film equals dry weight divided by solids fraction, cell volume equals wet film divided by transfer efficiency, taking 0.4 to 0.6 for gravure and 0.5 to 0.7 for a chambered flexo	Cells load and wear continuously; a roll that has lost 25 to 30 % of its volume delivers a coating that meets every specification in the drum and every fault in the reel
Crosslinker addition and pot life	Dose only to the recommended addition for the grade, and only into the volume that will be used inside the stated pot life, typically 8 to 12 h for a polycarbodiimide at pan temperature	Record the addition in the pan log with the time it was made; track viscosity on the same ISO 2431 cup at 25 C hourly after dosing, and run ISO 3251 solids before and after a long run	Viscosity climbs over hours once the crosslinker is in, and dry coat weight moves with it; the pan cannot be corrected back with water, because water lowers solids without reversing the reaction. Handle the crosslinker in chemical-resistant gloves and eye protection with local extraction running, and do not decant it over an open pan
Ambient humidity, hall and reel store	Coating hall as steady as the plant allows; reel store recorded, because the blocking figures are quoted against 50 C for the standard grades and 40 C for UniSeal-545LT	Calibrated hygrometer and a max-min thermometer in the store itself, logged daily, not a figure taken from the weather report	High RH lengthens the drying curve at constant dryer settings, and a Greater Noida store passing 40 C in June consumes most of the low-temperature grade's blocking margin before the reel is ever used

Functional CoatingsControl variables

The mechanism

The sealing window is one softening event, read twice

Operators treat seal initiation and blocking as two separate properties they can trade against each other. They are the same polymer softening, read from the jaw on one side and from the warm reel under pressure on the other, and they move together but not degree for degree. UniSeal-530LK initiates at 120 C and shows no blocking after 24 h at 50 C and 50 % RH under 10 kPa; UniSeal-545LT initiates at 90 to 100 C and only at 40 C on the same test. Roughly 20 to 30 C bought at the jaw costs about 10 C of permissible store temperature. Quote both figures together, and never specify a low-initiation grade without a storage condition attached.

Functional CoatingsThe mechanism

02 | 20 faults

Faults

Symptom, cause, check, change, confirm. The trap is the move to avoid.

Fault 1 of 20

Seal will not make at the jaw the line can reach

WHAT YOU SEE

The filler is set at its maximum jaw temperature and the seals still pull apart in the hand, or peel at a load well under the figure on the data sheet. The operator usually reports it as "the lacquer has gone weak".

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Dry coat weight below specificationThere is not enough polymer at the interface to flow and wet both faces in the dwell available, so the seal is made by whatever film happens to be over the fibre or foil peaks.
Jaw face temperature is well below the set-pointCartridge heaters age and Teflon tape builds up, so the panel reads 180 C while the face delivers 155 C, which is below the working window for a PET grade.
Dwell too short for the temperature being usedSeal initiation is defined at a dwell and a pressure; at 0.2 s the same lacquer needs 15 to 25 C more jaw than it needs at 0.5 s, because the heat has to cross the substrate before it reaches the lacquer.
Wrong grade for the substrateUniSeal-510PS initiates at 130 C on polystyrene and 150 C on polypropylene, and UniSeal-515PT needs 170 C on APET and CPET; a PS grade put on a PET tray will never reach the load.
Residual moisture or carrier in the filmA lacquer that went to the rewind holding water plasticises and then re-hardens unevenly in the reel, and the seal made from it is soft and inconsistent.

Functional CoatingsSeal will not make at the jaw the line can reach

Fault 1 of 20 · continued

Seal will not make at the jaw the line can reach

CHECK, IN THIS ORDER

Cut and weigh a known area of the coated web at both edges and the centre, against uncoated base from the same reel, and compare with the TDS coat weight in g/m2.
With the jaw drive isolated and locked off and the pneumatics bled, fit a surface thermocouple or a thermal indicating strip to the jaw face, then read it on a single controlled closure and compare with the machine set-point.
Read the actual dwell from line speed and jaw length, and take the actual pressure at the jaw with pressure-indicating film on that same closure rather than off the air-line gauge.
Make a laboratory seal series to ASTM F2029 at 10 C steps, one side heated, 0.5 s at 0.2 N/mm2, and pull to ASTM F88 at 300 mm/min 24 h later to find where this reel really initiates.
Confirm the substrate identity: PS, PP, APET or CPET, and whether the tray flange is the material the specification assumed.

THEN CHANGE

Restore coat weight to the TDS figure by cell volume first, viscosity and solids second.
Service the jaw cold and electrically isolated: strip the tape, replace failed heaters, re-profile the face, then re-verify with the thermocouple.
Increase dwell if the machine allows it, in preference to jaw temperature, because dwell buys seal without spending blocking margin.
If the line genuinely cannot reach 180 C at 0.5 s, move to UniSeal-545LT rather than lengthening dwell, since a longer dwell puts the heat into the tray and distorts the flange.
Where the seal is to polyethylene, change to the ethylene-acrylic acid or ionomer based grade; an acrylic lacquer will not key to untreated PE at any temperature.

CONFIRM IT IS FIXED

A seal series to ASTM F2029 followed by ASTM F88 on 15 mm strips at 300 mm/min, 23 C and 50 % RH, 24 h after sealing, giving the TDS load at a jaw temperature at least 10 C above the measured seal initiation temperature for this reel and at least 10 C below the top of the working window for that grade and substrate, with five strips within 15 % of each other.

THE TRAP

Winding the jaw up to the stop. Above the window the lacquer flows out of the seal and thins, so the load stops rising and then falls, the peel turns to tear, and the reel now needs a blocking margin the grade does not have.

Functional CoatingsSeal will not make at the jaw the line can reach (continued)

Fault 2 of 20

Coat weight is under specification

WHAT YOU SEE

Everything downstream is slightly wrong at once: seal load a little soft, kit rating a point low, Cobb a few grammes high. Nothing on the drum certificate is out of range.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Solids have fallen because water was added to hold a cup readingEvery correction to viscosity with water lowers solids, and dry coat weight follows solids directly while the wet film stays the same. This is the cause that happens every shift, which is why it is first.
Doctor blade pressure or angle changed on a previous shiftA harder blade setting wipes more out of the cells, and on a chambered system it also changes how the chamber fills at speed.
Line speed raised without re-setting the headOn some heads the transferred volume falls at higher speed as the cells have less time to release, so the same setting gives less film at 300 m/min than at 180 m/min.
Anilox or gravure cells loaded or wornVolume is what sets laydown, not ink strength, and a roll that has lost 25 to 30 % of its volume delivers proportionally less dry film at every other setting held constant. It does not happen inside a run, so look here after the first three.

Functional CoatingsCoat weight is under specification

Fault 2 of 20 · continued

Coat weight is under specification

CHECK, IN THIS ORDER

Cut and weigh a known area, three positions across the web, against uncoated base from the same reel, and report g/m2 dry against the TDS.
Run ISO 3251 solids on a sample drawn from the pan, not from the drum.
Read the ISO 2431 4 mm cup at 25 C on the pan sample, and record the pan temperature and the cup type alongside it.
Measure the roll volume in cm3/m2 by interferometry or a calibrated volume check rather than reading the end cap.
Compare the coating log for this reel with the log for the last reel that passed.

THEN CHANGE

Bring solids back to the supplied figure with fresh coating rather than correcting the cup with water.
Reset blade pressure to the lightest setting that wipes cleanly, then re-weigh.
Clean or replace the anilox or gravure cylinder; a chemical clean recovers a loaded roll, nothing recovers a worn one.
Go to a second pass rather than a heavier single pass where the target is above about 5 to 8 g/m2, because a single heavy pass on an absorbent base mottles and still does not reach the kit or Cobb figure.
If the head cannot deliver the weight at the required speed, re-specify the cell volume in cm3/m2 for that speed rather than running the line slow permanently.

CONFIRM IT IS FIXED

Three cut-and-weigh samples across the web, each within 10 % of the TDS coat weight, held over 500 m of production at the intended line speed, with the downstream kit, Cobb or seal figure back inside acceptance.

THE TRAP

Thinning to "improve transfer". It does move the wet film, and it lowers solids at the same time, so the dry coat weight goes down while every gauge on the line says the correction worked.

Functional CoatingsCoat weight is under specification (continued)

Fault 3 of 20

Blocking in the reel

WHAT YOU SEE

The reel will not unwind cleanly, the lacquer picks to the reverse face, and in the worst case the web tears or the print lifts. It is often found days after coating, in the store or at the filler.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Web rewound warmBlocking and seal initiation are the same softening event read from two sides; a reel built at 45 C is already inside the softening band of a low-temperature grade and is under pressure for weeks.
Reel store temperature above the grade's blocking figureThe standard grades are specified at no blocking after 24 h at 50 C and 50 % RH under 10 kPa, UniSeal-545LT at 40 C; a Greater Noida store in June sits at or above the 545LT figure.
Rewind tension too highBlocking is a function of pressure as well as temperature, and a hard-wound reel multiplies the load on the inner wraps well beyond the 10 kPa of the test.
Residual moisture in the filmWater left in the lacquer plasticises it and lowers its effective softening point, so a reel dried at speed with the same set-points blocks where the slower reel did not.
Low-temperature grade specified on its seal figure aloneSeal initiation and blocking move together, though not degree for degree: moving from UniSeal-530LK to UniSeal-545LT buys 20 to 30 C at the jaw and costs about 10 C of permissible store temperature, from 50 C to 40 C. Nobody writes the second half down.

Functional CoatingsBlocking in the reel

Fault 3 of 20 · continued

Blocking in the reel

CHECK, IN THIS ORDER

Take the web temperature with an infrared thermometer at the chill roll exit and on the outer wrap of the finished reel.
Read the reel store max-min thermometer and hygrometer, not the weather report.
Run the block test on a fresh sample to the written in-house method: face to reverse, 24 h at the grade's stated temperature and 50 % RH under 10 kPa, then separate on a tensile tester at a stated rate.
Check rewind tension taper against the machine recipe and measure hardness down the reel.
Weigh the coat: an over-weight lacquer blocks at a lower temperature than the same grade at specification.

THEN CHANGE

Get the web below 35 C at the chill roll, below 30 C for UniSeal-545LT, before the reel is built; service the chill water circuit if the roll is fouled.
Reduce rewind tension and taper it properly to the core.
Reduce line speed or raise air volume until the film is genuinely dry, and re-check web temperature at the tunnel exit.
Move the reel store, or condition it, or accept a shorter stock life in writing; a blocking specification with no storage condition attached is not a specification.
If the line cannot hold a cool store, move up from UniSeal-545LT to a standard grade and buy the jaw temperature back with dwell.

CONFIRM IT IS FIXED

Face-to-reverse block test to the written in-house method based on ASTM D1146 or ASTM D3354, at the grade's stated temperature and 50 % RH under 10 kPa for 24 h, separating at the stated rate with a recorded separation force, no lacquer transfer, no print lift and no audible pick, on a reel wound from the corrected settings.

THE TRAP

Adding wax or slip to the lacquer to stop the picking. It masks the block for a fortnight, then reports at the filler as a seal that will not make, because the same wax sits in the seal interface; that is the reel-age seal loss fault below, bought deliberately.

Functional CoatingsBlocking in the reel (continued)

Fault 4 of 20

Seal strength falls as the reel ages, with nothing changed at the coater

WHAT YOU SEE

A reel that sealed correctly in week one seals soft in week four, or the outer wraps seal and the inner wraps do not. Laboratory seals on freshly coated web from the same job still pass. The lacquer face can feel slightly waxy to the hand.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Slip additive migrating out of the film to the lacquer faceErucamide and the other amide slip additives migrate to the film surface over days and weeks, and in the reel they transfer to whatever is wound against them, so the additive collects on the very face that has to make the seal.
Slip or wax transferring from the reverse printed faceOverprint varnish and the slip package in the ink transfer to the lacquer in the reel; the seal interface is then part additive and the lacquer cannot wet the opposite face.
Wax or slip added to the lacquer to cure a blocking complaintIt holds the block for a fortnight and then reports at the filler, because the same wax sits in the seal interface and does exactly what it was added to do.
Antiblock particles at the seal faceSilica or talc antiblock in the sealant film holds the two faces apart at each particle, so the area actually sealed is less than the seal land, and the load falls with it.
Reel age and store temperatureMigration is a temperature clock like blocking; a construction that held for two months in January can be soft in six weeks in June.

Functional CoatingsSeal strength falls as the reel ages, with nothing changed at the coater

Fault 4 of 20 · continued

Seal strength falls as the reel ages, with nothing changed at the coater

CHECK, IN THIS ORDER

Make ASTM F2029 seals on freshly coated web and on the aged reel at the same jaw temperature, dwell and pressure, pull both to ASTM F88, and treat a fresh-to-aged gap of more than 15 % as migration until proved otherwise.
Ask the film supplier for the slip and antiblock package, the addition level in the sealant and on the reverse face, and the extrusion date of the reel.
Measure the coefficient of friction to ASTM D1894 on the coated face at coating and again on the aged reel; a falling COF over reel age is the additive arriving.
Wipe a strip of the lacquer face with a solvent-damped swab under local extraction, in gloves and eye protection, let it dry, re-seal and re-pull; a recovered load points at surface contamination and not at the lacquer.
Read the pan additive log and confirm whether wax or slip was ever added to this job.

THEN CHANGE

Take the additive out of the lacquer and cure the blocking at the rewind temperature and in the store instead.
Ask the film supplier for a low-slip or slip-free sealant, or a film carrying its slip package on the outer face only.
Shorten the interval between coating and filling and rotate stock first in, first out.
Hold the coated reel below the grade's stated blocking temperature; migration and blocking run on the same clock.
Re-qualify seal strength on aged material, not only on fresh web, and write the qualified reel age and store condition into the specification.

CONFIRM IT IS FIXED

ASTM F88 on 15 mm strips at 300 mm/min, 24 h after sealing, taken from a reel held at the agreed store condition for the full qualified period, inside the TDS range and within 15 % of the result from freshly coated web on the same construction.

THE TRAP

Raising the jaw temperature to recover an aged reel. It makes a seal today, spends blocking margin on a reel that is already warm, and the next call is the same reel picking in the store.

Functional CoatingsSeal strength falls as the reel ages, with nothing changed at the coater (continued)

Fault 5 of 20

Kit rating or Cobb60 fails on the coated board

WHAT YOU SEE

The drum is in specification and the laboratory drawdown passed, but board off the machine gives kit 7 where 10 was expected, or a Cobb60 of 20 g/m2 against a target of 8 to 15.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

One pass where the construction needs twoThe first pass is spent bridging the fibre peaks of an uncalendered base, so a single pass never reaches the low end of the Cobb range no matter what the total weight says.
Coat weight below targetUniBar-610GW gives kit 9 to 11 at 6 to 8 g/m2 and 11 to 12 only at 10 to 12 g/m2 in two passes; two grammes short of target is a full kit point.
Base board changedBarrier is a property of the finished construction, so a different mill, a different calendering or a higher base roughness moves the result with nothing in the coating having changed.
Pinholes from entrained airA pinhole is a barrier failure, and a hot oil or a kit reagent finds it while a visual inspection does not.
Film not fully coalescedA dispersion that dried too fast or too cool leaves a discontinuous film that looks glossy and leaks.

Functional CoatingsKit rating or Cobb60 fails on the coated board

Fault 5 of 20 · continued

Kit rating or Cobb60 fails on the coated board

CHECK, IN THIS ORDER

Cut and weigh the coat, per pass where the line has two heads, before any laboratory test is booked.
Hold the sheet to a strong light and look for pinholes.
Compare the base board certificate, roughness and grammage with the one the original approval was run on.
Run TAPPI T 559 with 3M kit reagents and ISO 535 Cobb60, both at 23 C and 50 % RH, on the machine-coated board and on the uncoated base for reference; the base typically runs 25 to 40 g/m2 Cobb60 before coating.
Confirm with a hot oil test, palm or coconut oil at 60 C for 30 min on the customer's own base.

THEN CHANGE

Split the weight into two passes with a full drying stage between them.
Restore coat weight to the TDS figure by cell volume first.
Re-qualify on the actual base board and re-issue the figure against that construction, or ask the mill for the base the approval was run on.
Cure the foam at source before dosing defoamer: slow the pump, stop the return line splashing, let the pan de-aerate.
Raise web temperature within the band for the substrate to complete coalescence, but not so far that the film skins before it levels.

CONFIRM IT IS FIXED

TAPPI T 559 kit at or above the TDS rating and ISO 535 Cobb60 inside the TDS range on machine-coated board at the measured coat weight, plus a hot oil test at 60 C for 30 min with no strike-through, all on the customer's own base.

THE TRAP

Treating the kit test as the answer. It is a screening method with a cold reagent; a hot fill or a hot oil will find a pinhole the kit reagent will pass, and the customer finds it in the field.

Functional CoatingsKit rating or Cobb60 fails on the coated board (continued)

Fault 6 of 20

Pinholes and craters in the barrier coat

WHAT YOU SEE

Small round holes or dished craters in an otherwise even film, worst in solids and in the second pass. Under a light the coating looks like it has been dusted with something.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Entrained air from the pump and return lineA dispersion that is being splashed into the pan carries air, and each bubble that reaches the web breaks and leaves a hole where the film has not closed.
Defoamer over-dosedOnce the silicone is over-dosed the craters are repellence, not foam, and no further addition corrects it.
Substrate surface energy too low, or the untreated face is being coatedWater-based coatings bead on anything much below 38 mN/m, so the film pulls back off low-energy spots into a crater; a reel loaded the wrong way up presents the untreated face and does this across the full width.
Contamination on the web: oil mist, silicone from a previous job, dust pulled in by staticA local low-energy spot is a local dewetting site, and a statically charged web collects fibre and dust into the wet film; the pattern repeats at the circumference of whatever roller is carrying it.
Second pass applied over a first pass that is not fully dryCarrier leaving the lower layer pushes through the upper one and vents as pinholes.

Functional CoatingsPinholes and craters in the barrier coat

Fault 6 of 20 · continued

Pinholes and craters in the barrier coat

CHECK, IN THIS ORDER

Watch the pan: look for a standing foam head and for the return line breaking the surface.
Check the defoamer addition log against the recommended dose before adding any more.
Measure surface energy with ISO 8296 test inks on the reel you are about to run, and check both faces to confirm which one is treated.
Map the defects: a repeating pitch points at a roller, a random scatter points at foam, static or contamination.
Check the static bars are on and earthed, and measure web temperature at the first tunnel exit to confirm the first pass is dry before the second head.

THEN CHANGE

Reduce pump speed, submerge the return line, and give the pan time to de-aerate before you touch the additive shelf.
Replace the batch if defoamer has already been over-dosed. Correcting a silicone-cratered coating on the line does not work; dilution into a substantially larger volume of fresh coating is the only recovery and is rarely worth it below a few hundred kilogrammes.
Restore treatment, turn the reel if the untreated face was loaded, or change to a primer where the base is genuinely low energy; UniPrimer 1340FP at 0.3 to 0.8 g/m2 is the usual answer on metallised and difficult film.
Clean the roller train, repair the static bars, and find the silicone source; a slitter oil or a nearby aerosol will keep re-seeding the fault.
Raise the first-pass drying, or slow the line, so the lower layer is dry before the second head.

CONFIRM IT IS FIXED

A 1 m2 area of coated web inspected over a light box with no pinholes visible, backed by a hot oil test at 60 C for 30 min on the customer's base with no strike-through, and a Cobb60 to ISO 535 inside the TDS range.

THE TRAP

Reaching for defoamer first. The usual cause is mechanical air, and a second dose of defoamer converts a foam problem you could have fixed with the pump into a repellence problem that costs you the batch.

Functional CoatingsPinholes and craters in the barrier coat (continued)

Fault 7 of 20

A peelable seal has gone to tear

WHAT YOU SEE

The lid no longer peels cleanly; it tears the lidding foil, delaminates the tray flange, or comes away with lacquer strings and residue on the flange. The load is higher than the specification, not lower.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Jaw temperature above the working windowPast the top of the window the lacquer flows and welds instead of forming an interfacial layer that can part, so the failure mode changes from peel to tear.
Coat weight above specificationMore lacquer at the interface means more material to part, and a peelable grade laid at 6 g/m2 instead of 3 to 4 g/m2 behaves like a lock seal.
Dwell or pressure raised to solve an earlier problemBoth put more heat and more contact into the interface, and both move the peel load the same way jaw temperature does.
Wrong grade for the trayUniSeal-510PS on an APET tray is being run far above its intended window to make any seal at all, and it welds when it finally does.
Tray flange material changedPeel is an interface property; a change from APET to CPET, or a new flange coating, changes it with nothing at the coater having moved.

Functional CoatingsA peelable seal has gone to tear

Fault 7 of 20 · continued

A peelable seal has gone to tear

CHECK, IN THIS ORDER

Run an ASTM F2029 seal series at 10 C steps and pull to ASTM F88 to map where peel becomes tear on this construction.
Cut and weigh the coat and compare with the 3 to 4 g/m2 specified for the peelable grades.
Verify jaw face temperature with a surface thermocouple and the pressure with pressure-indicating film, with the jaw drive isolated while the sensor is fitted.
Examine the peeled flange under a loupe: interfacial peel at constant load, no stringing and no residue is what the grade is designed to give.
Confirm the tray specification and supplier against the one the approval was run on.

THEN CHANGE

Bring the jaw back to the middle of the working window: about 155 C for UniSeal-510PS on polystyrene (window 140 to 170 C) and about 175 C on polypropylene (window 160 to 190 C); about 195 C for UniSeal-515PT on APET and CPET (window 180 to 210 C).
Reduce coat weight to the specified 3 to 4 g/m2.
Return dwell and pressure to the reference condition of 0.5 s at 0.2 N/mm2 and re-map.
Change to the grade matched to the tray rather than running one grade across a mixed tray fleet.
Re-qualify on the new tray and issue the window against it.

CONFIRM IT IS FIXED

An ASTM F88 pull on 15 mm strips at 300 mm/min, 24 h after sealing, giving a load inside the TDS range with interfacial peel at a roughly constant load, no stringing, and no lacquer left on the flange, across five strips.

THE TRAP

Reducing jaw temperature until the peel looks right but the seal is now at the very bottom of its window. The pack passes on the bench and fails at the first cold start of the filler, when the jaw is 15 C down and the seal does not make at all.

Functional CoatingsA peelable seal has gone to tear (continued)

Fault 8 of 20

Foam in the pan, and a viscosity that is not viscosity

WHAT YOU SEE

A standing head of foam on the pan, streaks and skips in the coating, and a cup reading that keeps climbing although nothing has been added. The operator adds water and it comes back within the hour.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Mechanical air from the circulation systemAir entrained by a fast pump or a splashing return line raises the apparent volume and makes the cup read long while the true dispersion viscosity has not moved.
pH falling through the runAmmonia leaves the open pan, the dispersion loses stability, and it genuinely thickens; adding water corrects the cup for ten minutes and makes the underlying condition worse.
Evaporation from the open panWater leaving the pan raises solids and viscosity together, which is a real rise and is corrected with water, but only once the other causes are ruled out.
Temperature of the pan below 25 CThe cup figures are quoted at 25 C, and a cold pan at start-up reads several seconds long; that is a real temperature effect on viscosity, not a change in the coating, so it is corrected at the pan and not in the drum.
A crosslinker has been dosed and the pot life is runningOnce polycarbodiimide or a similar crosslinker is in, viscosity climbs over hours and does not come back; water lowers solids without reversing the reaction, so the coat weight falls while the cup still reads long.

Functional CoatingsFoam in the pan, and a viscosity that is not viscosity

Fault 8 of 20 · continued

Foam in the pan, and a viscosity that is not viscosity

CHECK, IN THIS ORDER

Look at the pan before you look at any instrument: a standing foam head answers the question.
Read pH with a calibrated electrode in the pan at running temperature.
Read the pan temperature with the cup sample and note it beside the viscosity figure.
Draw a sample, let it stand 10 min in a beaker and re-read the ISO 2431 4 mm cup at 25 C; if it has dropped several seconds, you were measuring air.
Read the pan log for a crosslinker addition and the time it was made, and run ISO 3251 solids on the pan sample against the drum figure.

THEN CHANGE

Reduce pump speed and submerge the return line so it no longer breaks the surface.
Restore pH with the supplied stabiliser with local extraction running, in goggles and chemical-resistant gloves: dose slowly below the liquid surface with the pan cover in place, circulate, then re-measure. Never dose ammonia into a hot open pan with the extraction off, and keep an eye-wash station within reach of the coating head.
Fit or repair a pan cover to slow evaporation on long runs.
Bring the pan sample to 25 C before reading, or record the temperature with every reading and treat it as a trend figure.
Where the pot life has run out, drop the pan and recharge with fresh coating; correct with water only when foam, pH, temperature and crosslinker have all been excluded, and re-run solids afterwards.

CONFIRM IT IS FIXED

An ISO 2431 4 mm cup reading at 25 C that is stable within 2 s over an hour of running, with pH inside 8.0 to 9.0, ISO 3251 solids within 2 percentage points of the supplied figure, and no standing foam on the pan.

THE TRAP

Adding water to the cup reading. It is the single most expensive habit in water-based coating: solids fall, dry coat weight falls with them, and the seal or barrier failure that follows two reels later is never traced back to the water.

Functional CoatingsFoam in the pan, and a viscosity that is not viscosity (continued)

Fault 9 of 20

Seal fails where product dust lands in the seal

WHAT YOU SEE

Pouches on a pan masala or mouth-freshener line leak or burst at random positions, while seals made on clean film in the laboratory pass easily. The leakers cluster where the filler drops product.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Product in the seal area, as designed-for rather than as a defectPowder and oil in the interface stop the two lacquer faces meeting, so the seal is made only across the clean fraction of the area.
Coat weight at the bottom of the rangeSealing through contamination is bought with lacquer; at the 4 g/m2 bottom of the 4 to 6 g/m2 range specified for UniSeal-530LK, rather than the 5 to 6 g/m2 that sealing through product actually needs, there is not enough film to flow around the particle.
Filler dosing or the dust extraction at the sealing stationMore product in the seal than the qualification assumed, particularly on a worn auger or with a static-charged film.
Oil content of the product higher than the qualification batchAn oily dust is far harder to seal through than a dry one, because the oil wets the lacquer face and prevents contact altogether.
Jaw profile flat where a serrated or ribbed jaw is neededA profiled jaw displaces particles out of the seal land; a flat jaw traps them in it.

Functional CoatingsSeal fails where product dust lands in the seal

Fault 9 of 20 · continued

Seal fails where product dust lands in the seal

CHECK, IN THIS ORDER

Open a run of failed pouches and look at the seal land under a loupe for embedded product before you touch any setting.
Run the contaminated-seal test: 10 mg of the customer's own product in the seal area, sealed at 150 C, 0.5 s, 0.2 N/mm2, pulled to ASTM F88, against a clean seal on the same construction.
Cut and weigh the coat against the 4 to 6 g/m2 for UniSeal-530LK.
Check the dust extraction, the static bar and the auger settle time at the sealing station.
Verify jaw profile, and jaw face temperature with a thermal strip fitted while the jaw drive is isolated.

THEN CHANGE

Take coat weight to the top of the range for UniSeal-530LK, 5 to 6 g/m2.
Fix the filler: settle time, dust extraction, static bar, so less product reaches the seal land.
Move to a profiled jaw where the machine allows it.
Re-qualify against the customer's own product at their loading, since a laboratory contaminant differs in quantity, particle size and oil content from the real one.
Where oil content is the driver, widen the seal land rather than raising the jaw.

CONFIRM IT IS FIXED

Contaminated-seal test with 10 mg of the customer's own product in the seal area at 150 C, 0.5 s, 0.2 N/mm2, retaining 60 % or more of the clean-seal load on the same construction, backed by a leak test on 200 consecutive pouches off the corrected filler.

THE TRAP

Quoting and setting the line to the clean-seal figure. The clean seal is not the condition the machine works in, and every adjustment made to reach a clean-seal number takes the line further from the one that matters.

Functional CoatingsSeal fails where product dust lands in the seal (continued)

Fault 10 of 20

Seal fails only where it is made over print or varnish

WHAT YOU SEE

Seals pass on unprinted areas of the same web and fail where the seal land crosses print, a registration bar or an overprint varnish. Ink often lifts into the seal land, and the peeled faces show ink on both sides.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Ink or varnish in the seal landThe lacquer is sealing to the ink film and not to the substrate, so the weakest interface in the pack becomes ink to substrate or ink to lacquer, and the seal load is whatever that interface carries.
Heavy coverage or wet trapping in the seal areaSolid coverage holds solvent or water in the seal land and stays soft under the jaw, so the interface never sets in the dwell available.
Slip or wax in the overprint varnishThe same additive that makes the print run sweetly on the press sits at the surface the lacquer has to wet, and the lacquer does not wet it.
Lacquer anchorage to printed or lacquered foil liddingOn a printed foil lid the lacquer is anchored to the ink, and ink adhesion to foil is a press property, so the seal can fail at the ink with the lacquer entirely correct.
The construction was qualified unprintedAn approval run on plain web does not describe the pack that is actually being sealed, and the window issued against it does not apply.

Functional CoatingsSeal fails only where it is made over print or varnish

Fault 10 of 20 · continued

Seal fails only where it is made over print or varnish

CHECK, IN THIS ORDER

Make ASTM F2029 seals on a printed area and an unprinted area of the same web at identical settings and pull both to ASTM F88.
Look at the peeled faces under a loupe: ink on both sides means the failure is at the ink, not in the lacquer.
Run a tape pull on the printed web before coating to establish whether the ink is anchored to the substrate or to the foil.
Ask the press for the coverage in the seal land and the varnish specification, including whether the varnish carries slip.
Cut and weigh the lacquer over a printed area and over an unprinted area; an ink film changes transfer and can change the laydown.

THEN CHANGE

Keep the seal land clear of print and of overprint varnish; that is a design change and goes back to the brand owner in writing.
Use a slip-free varnish in the seal land, or leave the varnish out of that area.
Fix ink anchorage at the press, by primer or by corona, before the lacquer is blamed.
Raise coat weight within the grade range so the lacquer has enough film to bridge the ink, where the design cannot be changed.
Re-qualify the seal on the printed construction and issue the window against it.

CONFIRM IT IS FIXED

ASTM F88 loads from printed and unprinted areas of the same construction, 24 h after sealing, both inside the TDS range and within 15 % of each other, with no ink transfer visible on the peeled faces.

THE TRAP

Judging the job on a seal made in the clear window. The pack is sealed where the print is, and an unprinted sample releases a reel that fails at the filler.

Functional CoatingsSeal fails only where it is made over print or varnish (continued)

Fault 11 of 20

Mottle and dry-back on an absorbent base

WHAT YOU SEE

A cloudy, uneven, orange-peel surface on coated board, sometimes with the gloss dying back over the following hour. It is worst on uncoated kraft and on heavy single passes.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Too much weight in one pass on an absorbent baseThe coating sinks unevenly into the fibre before it can level, so the surface follows the absorbency pattern of the board rather than the metering.
Base board absorbency variable or the base uncalenderedThe first pass is consumed bridging the fibre peaks, and where the peaks are higher it is consumed entirely.
Drying too fast at the tunnel entryA skin forms before the film levels, which locks the mottle in and also traps carrier under it.
Viscosity too high for the cell volume in useA coating that will not release cleanly from the cells prints the cell pattern, which reads on board as fine mottle.

Functional CoatingsMottle and dry-back on an absorbent base

Fault 11 of 20 · continued

Mottle and dry-back on an absorbent base

CHECK, IN THIS ORDER

Cut and weigh, per pass, and check whether the weight is being laid in one pass or two.
Run a Cobb60 to ISO 535 on the uncoated base at three positions to quantify the absorbency variation.
Read the tunnel zone profile and the web temperature at the tunnel entry, not only at the exit.
Read the ISO 2431 4 mm cup at 25 C on the pan against the TDS range for the grade.
Look at the mottle under a loupe: a regular cell pattern is a metering fault, an irregular cloud is absorbency.

THEN CHANGE

Split the weight into two passes, each fully dried.
Lay a lower-weight sealing pass first so the second pass has a closed surface to level on.
Soften the first drying zone and put the heat later in the tunnel so the film levels before it skins.
Bring viscosity to the lower end of the TDS range for the grade, correcting with fresh coating rather than water where possible.
If the base board genuinely will not take the coating, take that back to the mill; it is a base problem and no metering change will hide it.

CONFIRM IT IS FIXED

Visual assessment of a 1 m2 coated area at grazing light with no cell pattern and no cloud, a Cobb60 to ISO 535 inside the TDS range at all three cross-web positions, and gloss to ISO 2813 stable between 5 min and 60 min after the tunnel.

THE TRAP

Raising coat weight to cover the mottle. On an absorbent base a heavier single pass mottles worse, not less, and you have now spent material, drying capacity and line speed to make the fault more visible.

Functional CoatingsMottle and dry-back on an absorbent base (continued)

Fault 12 of 20

Lacquer picks up on the sealing jaw

WHAT YOU SEE

A brown or glassy deposit builds on the jaw face over a shift, seals go dirty and inconsistent, and the machine needs cleaning every few hours. Often reported as "the lacquer is burning".

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Jaw temperature above the working windowPast the window the lacquer flows, wets the jaw face and transfers, then bakes on.
Coat weight above specificationExcess lacquer squeezes out of the seal land onto the jaw face, where it has nowhere to go but onto the tool.
Teflon facing worn throughBare metal grips softened lacquer that the Teflon would have released; the deposit then grows on itself.
Film still holding carrier at the fillerA lacquer that went to the reel wet is softer at any given jaw temperature and transfers at settings that were previously clean.

Functional CoatingsLacquer picks up on the sealing jaw

Fault 12 of 20 · continued

Lacquer picks up on the sealing jaw

CHECK, IN THIS ORDER

Verify jaw face temperature against the top of the grade's working window with a surface thermocouple fitted while the jaw drive is isolated and locked off, read on a single controlled closure.
Inspect the Teflon facing for wear, scoring and tape overlap with the jaw cold.
Cut and weigh the coat against the TDS.
Run an ASTM F2029 series to establish the lowest jaw temperature that still gives the required ASTM F88 load on this construction.
Check web temperature at the coater chill roll exit and the reel store condition for the reel currently running.

THEN CHANGE

Drop the jaw to the middle of the window rather than the top, using dwell to recover any lost load.
With the jaw cooled to hand temperature and electrically isolated, re-face with fresh Teflon, butt-jointed, not overlapped.
Bring coat weight back to specification.
Return to a properly dried reel; if the reel was rewound warm it will keep doing this whatever the filler is set to.
Where the pack genuinely needs the top of the window, move to a grade whose window sits higher, rather than running this one at its limit.

CONFIRM IT IS FIXED

Four hours of continuous running with no visible deposit on the jaw face and ASTM F88 seal loads across that period within 15 % of each other on the corrected settings.

THE TRAP

Turning the jaw up because the seals have gone dirty and inconsistent. The dirt is transfer caused by heat, so more heat produces more transfer, and the shift ends with a machine that has to be stopped and scraped.

Functional CoatingsLacquer picks up on the sealing jaw (continued)

Fault 13 of 20

Primer fails on metallised film

WHAT YOU SEE

The print or the coating over the primer lifts on tape, or the aluminium itself comes away with the tape and leaves clear film behind. Often intermittent down the reel.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

The metallising bond itself is the weak linkIf the aluminium transfers with the tape, no primer will fix it; the pack is failing at the metal-to-film interface and that belongs to the film supplier.
Treatment has decayed on the reelSurface energy on metallised BOPP and PET falls with reel age and store temperature, and a certificate issued at 42 mN/m three months ago is commonly 34 to 36 mN/m on the day you coat.
Primer coat weight too high on filmWater-based primers on film work at 0.3 to 0.8 g/m2; laid heavier they coalesce into a soft continuous layer that is weaker than the metal bond under it, so the failure moves into the primer.
Primer not fully dried or cured before the next stationA primer that still holds water has not developed its own cohesion, and the ink over it keys to a soft layer.
Wrong primer chemistry for the jobA UV LED primer and an aqueous PUD primer solve different problems; UniPrimer 1345FU crosslinks into a continuous network at 1.0 to 2.0 g/m2 and is the exception to the 1.0 g/m2 ceiling that applies to coalescing water-based films on film.

Functional CoatingsPrimer fails on metallised film

Fault 13 of 20 · continued

Primer fails on metallised film

CHECK, IN THIS ORDER

Look at the tape from the failed pull first: clear film behind it means the aluminium came away and the fault is at the metal-to-film interface, not the primer. Stop here and take it back to the film supplier.
Measure surface energy with ISO 8296 test inks on the reel you are about to run, at both edges and the centre.
Run a tape pull on the primed, unprinted web and again on the printed web with a defined tape, for example 3M 610 or equivalent, 25 mm wide, applied with a stated roller pass and pulled at a stated angle and speed, and report which interface released: primer to metal, metal to film, or ink to primer. Keep the ISO 2409 cross-cut for coatings on board or another substrate that supports the cut, because on 12 to 20 micron metallised film the blade severs the metallising and the class returned is an artefact of the cut.
Cut and weigh the primer coat against 0.3 to 0.8 g/m2 for UniPrimer 1340FP or 1.0 to 2.0 g/m2 for UniPrimer 1345FU.
For the UV grade, measure both delivered dose in mJ/cm2 and peak irradiance in W/cm2 with a radiometer banded for 385 to 405 nm, and check cure with an ASTM D5402 MEK double-rub. Handle uncured primer as a skin sensitiser: nitrile gloves, no skin contact, no solvent washing of skin, contaminated clothing removed immediately. Do the MEK rub under local extraction or in a hood, away from ignition sources, in gloves and eye protection. Do not look into a running LED array and do not defeat the emitter interlocks.

THEN CHANGE

Reject the reel back to the film supplier where the metal bond is the failure, or re-treat in line where the loss is treatment only.
Bring primer weight down to the specified range on film.
Dry the primer properly: 60 to 80 C air, 1.5 to 3 s dwell, and confirm the web temperature with the infrared thermometer.
Move to UniPrimer 1345FU where the line has LED and the aqueous primer cannot be dried in the dwell available.
Re-qualify adhesion on the customer's own metallised reel, because bond is an interface property of the construction and not a property of the primer.

CONFIRM IT IS FIXED

A defined tape pull on the primed and on the printed web, 24 h after coating, on the customer's own metallised film at the measured primer weight, showing no metal transfer and no primer removal, with the failing interface identified where anything does release; backed by an ASTM D5402 MEK double-rub figure on the UV grade.

THE TRAP

Doubling the primer to "get more adhesion". Above about 1.0 g/m2 an aqueous primer on film becomes the weakest layer in the stack, so the tape test gets worse and the operator concludes the primer is faulty.

Functional CoatingsPrimer fails on metallised film (continued)

Fault 14 of 20

WVTR passes flat, fails after creasing

WHAT YOU SEE

A flat panel of coated board meets the WVTR specification comfortably, and the same board measured after creasing, folding and gluing does not. Cartons in the field take up moisture at the score lines.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

The barrier film cracks at the creaseA coating that is hard enough to give a low Cobb can be too brittle to follow a score; the crack is a metre of open path per carton and it is invisible.
Coat weight below target on the crease sideA thin film has less to give at the fold, so it opens where a film at the specified 8 to 12 g/m2 in two passes would stretch.
Creasing rule and matrix set too tight for the coated boardThe score profile that suited the uncoated base cuts rather than folds the coated construction.
Board over-dried in the coating tunnelBoard that has lost too much of its own moisture is brittle, and the coating fails because the fibre under it fails first.

Functional CoatingsWVTR passes flat, fails after creasing

Fault 14 of 20 · continued

WVTR passes flat, fails after creasing

CHECK, IN THIS ORDER

Run ASTM F1249 on a flat panel and on a creased-and-flattened panel from the same sheet and compare, quoting the condition, 38 C and 90 % RH or 23 C and 85 % RH, with every number.
Examine the crease under a loupe or low-power microscope for coating cracks.
Cut and weigh the coat, and check it is in two passes, not one.
Measure board moisture before and after the tunnel.
Check the creasing rule height and matrix width against the coated board caliper, not the base caliper.

THEN CHANGE

Move to a more flexible grade or a lower crosslinker addition where crease performance matters more than the last unit of Cobb.
Restore coat weight to 8 to 12 g/m2 in two passes for UniBar-625MB.
Widen the matrix and reduce rule penetration so the board folds rather than cracks.
Reduce tunnel temperature within the band so the board keeps its own moisture.
Re-issue the WVTR figure against the converted carton, not the flat panel, since barrier belongs to the finished construction.

CONFIRM IT IS FIXED

ASTM F1249 on the creased and reformed construction, quoted at 38 C and 90 % RH, inside the TDS range for the coat weight used, together with a loupe inspection of the score showing no continuous crack.

THE TRAP

Re-testing the flat panel to prove the coating is fine. It is fine, and it is not what the pack is made of; the customer's failure is at the score and the flat panel will never show it.

Functional CoatingsWVTR passes flat, fails after creasing (continued)

Fault 15 of 20

Coated board curls or the reel telescopes

WHAT YOU SEE

Sheets bow towards the coated side after the coater, reels telescope or dish, and the converting line jams. Worst on light board and in low-humidity months.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

One-side coating with a moisture imbalanceThe coated side is wetted and then dried harder than the uncoated side, so the two faces end at different moisture contents and the sheet curls towards the drier face.
Tunnel over-driedTaking the board well below its equilibrium moisture maximises the imbalance and the curl with it.
Rewind tension untaperedA reel wound hard to the core with no taper walks under its own stored stress, particularly on a coated, slippery surface.
High coat weight on light boardThe heavier the coating relative to the base, the more the coated face dominates the dimensional behaviour.

Functional CoatingsCoated board curls or the reel telescopes

Fault 15 of 20 · continued

Coated board curls or the reel telescopes

CHECK, IN THIS ORDER

Measure board moisture on both faces before the coater and after the chill roll.
Read the tunnel zone profile and web temperature at the exit with an infrared thermometer.
Check the rewind tension recipe for taper and measure reel hardness from core to outside.
Measure the coating friction with an ASTM D1894 slide test where the reel is walking on a slippery coated face.
Cut a 200 mm square from the finished reel, lay it flat, condition at 23 C and 50 % RH for 24 h and measure the curl height.

THEN CHANGE

Drop tunnel temperature to the lowest that still dries the film, and re-check web temperature.
Add a moisture-restoring station or a light water spray on the reverse where the line has one.
Taper rewind tension properly to the core and reduce the core tension.
Condition the reel at 23 C and 50 % RH before converting.
On light board, reduce coat weight to the bottom of the range, or split the construction so less weight sits on one face.

CONFIRM IT IS FIXED

A 200 mm square cut from the reel, conditioned 24 h at 23 C and 50 % RH, sitting with a curl height inside the converter's acceptance, and a reel that runs the converting line without telescoping over a full shift.

THE TRAP

Winding tighter to stop the telescoping. A tighter reel stores more of the stress that is causing the walk, and it also raises the pressure on the inner wraps, which brings a blocking fault to a job that did not have one.

Functional CoatingsCoated board curls or the reel telescopes (continued)

Fault 16 of 20

OTR rises sharply in humid weather

WHAT YOU SEE

Oxygen transmission on the same construction that measured below 1 cm3/m2.24h.bar dry comes back at 20 to 80 in the monsoon, and packed product goes off in the field in July and not in January.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

The oxygen layer is polar and plasticises with waterThe polyvinyl-alcohol based UniBar-630OB loses most of its barrier as relative humidity rises; this is the polymer, not the coat weight, and it is why the hydrophobic layer goes over it and not under it.
Moisture top coat missing, thin, or under the oxygen layerWithout UniBar-625MB over it, the oxygen coat sits open to ambient humidity and behaves at its wet-condition figure all the time.
Test condition not quoted with the numberThe same sample reads below 1 dry, 2 to 10 at 50 % RH and 20 to 80 at 80 % RH; an unqualified figure is not comparable with anything.
Pinholes or crease cracks in the top coatA defect in the hydrophobic layer lets moisture reach the oxygen layer locally and the whole construction reads at its wet figure.

Functional CoatingsOTR rises sharply in humid weather

Fault 16 of 20 · continued

OTR rises sharply in humid weather

CHECK, IN THIS ORDER

Run the oxygen transmission at the customer's actual storage humidity to ASTM F1927, which is the coulometric method at controlled relative humidity and temperature; ASTM D3985 covers the dry figure only. Record temperature, carrier-gas RH and test-gas RH with every result.
Confirm the layer order on a cross-section or by selective dissolution: the oxygen base coat must be under the moisture top coat.
Cut and weigh both layers: 2 to 4 g/m2 for UniBar-630OB on 12 micron PET, 8 to 12 g/m2 in two passes for UniBar-625MB.
Inspect the top coat over a light box for pinholes and at the score for cracks.
Check the reel store and the filling hall humidity with a calibrated hygrometer.

THEN CHANGE

Apply or restore the moisture top coat over the oxygen layer at the specified weight and pass count.
Fix pinholes at source: pan foam, pump speed, surface energy.
Re-quote the specification at the pack's real storage condition rather than at 0 % RH.
Where the storage condition genuinely cannot be met by the coating stack, say so and take the construction back to design; a coating cannot carry a barrier the polymer class does not have.
Protect the coated reel in moisture-barrier wrap between coating and converting.

CONFIRM IT IS FIXED

ASTM F1927 on the finished construction at 23 C and the customer's storage humidity, inside the TDS range for that condition, with the temperature and both humidities written on the result, repeated on three samples across the web; the dry figure to ASTM D3985 quoted separately and labelled as dry.

THE TRAP

Adding coat weight to the oxygen layer to recover the number. The loss is a plasticisation of the polymer by water and it is largely independent of thickness, so the extra weight costs money, costs drying capacity and does not move the reading.

Functional CoatingsOTR rises sharply in humid weather (continued)

Fault 17 of 20

Seal strength varies across the web

WHAT YOU SEE

Pouches or lids made from one edge of the web pass and the other edge is soft, or the middle is strong and both edges weak. The average passes; the failures are all on one side.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Coat weight profile across the webBlade wear, chamber starvation at the ends and cylinder deflection all put a different film on the edges than the centre, and seal load follows coat weight.
Jaw face temperature profileA jaw with a failed end heater or uneven tape build-up runs 15 to 25 C cooler at one end, and that end never reaches its initiation temperature.
Drying profile across the tunnelAn unbalanced air knife dries one edge harder, so one edge goes to the reel with carrier still in it and seals soft.
Substrate profileCaliper, treatment and flange geometry vary across a reel or a tray tool, and seal is an interface property.

Functional CoatingsSeal strength varies across the web

Fault 17 of 20 · continued

Seal strength varies across the web

CHECK, IN THIS ORDER

Cut and weigh at five positions across the web, not three, and plot the profile.
With the jaw drive isolated and locked off, place thermal indicating strips at five positions along the jaw face, then read the profile on a single controlled closure.
Make ASTM F2029 seals from the same five web positions and pull all of them to ASTM F88 at 300 mm/min, 24 h later.
Measure surface energy with ISO 8296 test inks at the same five positions.
Check the tunnel air balance and the chamber fill at both ends of the coating head.

THEN CHANGE

Correct the coating profile: blade condition, chamber end seals, cylinder alignment.
Repair the jaw heater profile with the jaw cold and isolated, and re-face evenly; butt the Teflon rather than overlapping it.
Balance the tunnel air knives and re-measure web temperature across the web.
Trim the affected edge where the profile cannot be corrected and the order allows it.
Re-qualify the corrected web across all five positions before releasing the reel.

CONFIRM IT IS FIXED

ASTM F88 loads from five cross-web positions, 24 h after sealing, all inside the TDS range and within 15 % of each other, with a coat weight profile flat to 10 % across the same five positions.

THE TRAP

Judging the reel on a sample cut from the middle. The centre is almost always the best part of the web, so a centre sample releases a reel whose edges will fail at the filler, and the failure arrives as a customer complaint rather than a quality hold.

Functional CoatingsSeal strength varies across the web (continued)

Fault 18 of 20

Hot tack fails at the filler, cold seal is fine

WHAT YOU SEE

Vertical form-fill-seal pouches burst or the seal opens as the product drops in, although a cold seal pulled the next day meets the specification comfortably.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Seal loaded before it has cooledHot tack is the strength of the seal while it is still hot, and it is a different property from cold seal strength; a lacquer can be strong cold and weak at 0.2 s.
No cooling jaw, or cooling jaw ineffectiveThe machine is asking the lacquer to carry the product drop before it has set, which is a machine timing problem expressed as a seal fault.
Jaw temperature too highOverheating leaves the seal softer for longer, so peak hot tack falls even though the cold seal rises.
Coat weight above rangeA thicker molten layer takes longer to cool through and carries less load at the moment the product arrives.
Product drop timing too early for the line speedEvery 50 ms earlier is 50 ms less cooling, and hot tack falls steeply over that window.

Functional CoatingsHot tack fails at the filler, cold seal is fine

Fault 18 of 20 · continued

Hot tack fails at the filler, cold seal is fine

CHECK, IN THIS ORDER

Time the product drop against the jaw-open signal on the machine; it costs minutes and settles two of the causes.
Check the cooling jaw is actually cooled, with a surface thermocouple on the face fitted while the drive is isolated, not with the water gauge.
Cut and weigh the coat against the grade range.
Measure hot tack to ASTM F1921 Method B at 0.2 s delay across a jaw temperature series and find the peak.
Compare that peak with the 2 to 4 N/15 mm typical for UniSeal-530LK on the stated construction.

THEN CHANGE

Set the jaw at the hot tack peak, which is usually below the cold-seal optimum, not at the top of the window.
Repair or fit the cooling jaw and verify its face temperature.
Delay the product drop, or reduce line speed, until the hot tack test and the machine agree.
Bring coat weight back into range.
Where the machine timing genuinely cannot be changed, move to a grade with a higher hot tack peak rather than trying to buy it with jaw temperature.

CONFIRM IT IS FIXED

ASTM F1921 Method B at 0.2 s delay giving the TDS hot tack figure at the jaw temperature the machine will run, backed by 200 consecutive filled pouches at full line speed with no burst and no seal opening.

THE TRAP

Raising the jaw temperature because the seal is failing. Hot tack peaks and then falls with temperature, so above the peak every degree added makes the burst rate worse while the cold seal test keeps saying the lacquer is fine.

Functional CoatingsHot tack fails at the filler, cold seal is fine (continued)

Fault 19 of 20

Grit, streaks and blinded filters

WHAT YOU SEE

Fine hard particles in the coating, continuous scratch lines down the web, and filters that blind within minutes of a change. The drum often looks separated or has a skin on it, or the fault arrives in the first hundred metres after a stop.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

The dispersion has been frozenA frozen dispersion coagulates irreversibly and does not recover on thawing; it looks acceptable after stirring and then blinds every filter on the line.
The drum was shaken rather than stirredShaking entrains air and shears the dispersion; the resulting micro-coagulum reads as grit and, in a barrier coating, prints as pinholes.
Coating dried in the cells, the chamber and on the blade over a stopA line left standing over a break or a shift change dries coating in the engraving and in the chamber end seals; it comes away as hard flakes and gives score lines and a step in coat weight over the first hundred metres.
pH has fallen far enough to destabilise the dispersionBelow the stability range the polymer starts to come out, and the first evidence is grit at the blade, not a number on a meter.
Skin from a part-used drum stirred back in, or a drum past its shelf lifeDried skin does not redissolve; it breaks into hard flakes that pass a coarse filter and lodge in the cells. An aged dispersion gives the same blinded filters: take twelve months for the lacquers and barrier coatings, six months for the water-based primers and the polyvinyl-alcohol oxygen base coat, and six months for the UV LED primer at 15 to 25 C in the dark.

Functional CoatingsGrit, streaks and blinded filters

Fault 19 of 20 · continued

Grit, streaks and blinded filters

CHECK, IN THIS ORDER

Filter a 500 ml sample through a 100 micron mesh and inspect and weigh the residue.
Check the drum history: manufacturing date and shelf life, store temperature log, part-used date, and whether it has been outside in winter.
Read pH with a calibrated electrode.
Inspect the drum for a skin and for separation before any stirring is done, and inspect the chamber, the end seals and the engraving after any stop.
Trace the line and pan history for the previous product run through them, and check the static bars where fibre and dust are in the film rather than coagulum.

THEN CHANGE

Reject a frozen, coagulated or out-of-date drum; it cannot be filtered back into specification.
Stir, never shake, and give a part-used drum a proper low-shear stir before use.
Skim and discard the skin rather than stirring it in.
Wash up properly at every stop: flush the chamber, strip and clean the end seals, and flood or wash the engraving rather than leaving coating to dry in it; run the first hundred metres after a start-up to waste and re-weigh the coat before releasing web.
Restore pH with the supplied stabiliser before the dispersion goes further out, and flush the line and pan thoroughly between products of opposite charge, recording the sequence.

CONFIRM IT IS FIXED

A 500 ml sample through a 100 micron mesh leaving no visible residue, stable pH inside 8.0 to 9.0 over an hour, and 500 m of coated web with no streak lines under grazing light and coat weight inside 10 % of the TDS figure.

THE TRAP

Straining the drum and running it anyway. The fine coagulum passes the strainer, reaches the cells and the coating head, and turns a rejected drum into a rejected reel plus a cylinder clean.

Functional CoatingsGrit, streaks and blinded filters (continued)

Fault 20 of 20

Repulpability result comes back short

WHAT YOU SEE

The coated board fails the recyclability test at the coarse-reject stage, or the handsheets show sheet adhesion, on a construction that passed at approval.

WHAT IT LOOKS LIKE

CAUSES, MOST LIKELY FIRST

Coat weight well above the qualified figureThe typical result is quoted at 8 to 12 g/m2 on a stated base; a construction running at 18 g/m2 puts more polymer film into the pulper than the method was qualified for.
Crosslinker over-dosedPolycarbodiimide added to chase water resistance makes the film harder to break up, and the coarse reject rises with it.
Base board changedRepulpability is a property of the finished construction; a different fibre furnish or an existing barrier layer on the base changes the answer with nothing in the coating having moved.
A different test method usedCEPI version 2, PTS-RH 021 and TAPPI UM 213 with the Fibre Box Association protocol do not give interchangeable numbers, and a result under one method cannot be read against an acceptance written for another.

Functional CoatingsRepulpability result comes back short

Fault 20 of 20 · continued

Repulpability result comes back short

CHECK, IN THIS ORDER

Cut and weigh the coat and compare with the qualified 8 to 12 g/m2.
Read the additive log for crosslinker addition against the recommended dose.
Confirm which method was run, at what consistency and temperature, and on what screen; the default here is repulping at 4 to 5 % consistency and 40 to 45 C with coarse reject on a 0.15 mm slotted screen.
Compare the base board certificate with the one used at approval.
Ask whether the failing sample was converted board with a laminate, window or adhesive on it, which the coating did not put there.

THEN CHANGE

Bring coat weight back to the qualified figure.
Reduce or remove the crosslinker and recover water resistance with a second pass instead.
Re-run the test on the customer's own base at the coat weight their machine lays down, and quote the figure against that construction.
Agree the method in writing before testing, because the acceptance and the method have to belong together.
Do not issue a claim beyond the tested construction.

CONFIRM IT IS FIXED

The agreed method run on the customer's own construction at the measured coat weight, returning coarse reject below 5 % of the charge, no sheet adhesion and fibre yield above 85 % of the fibre in the base board, with the method and the construction recorded alongside the result.

THE TRAP

Describing the board as certified or compliant once one test passes. Regulation (EU) 2025/40 applies from 12 August 2026, but its design-for-recycling performance grades come through delegated acts that have not yet been adopted, due by 1 January 2028, so nothing can be certified against them today; check the status before this document is reprinted. The honest wording remains: repulpable, tested to the named method on the named construction.

Functional CoatingsRepulpability result comes back short (continued)

At the press

One page to work from, and the methods behind every number.

Quick reference

One page at the press

Symptom	Check this first	Change this first
Seal will not make at the available jaw temperature	Cut and weigh the coat; thermocouple on the jaw face, drive locked off	Restore coat weight, then buy load with dwell, not jaw
Peelable seal has gone to tear	ASTM F2029 series at 10 C steps, pulled to ASTM F88	Bring jaw to mid-window and coat weight to 3 to 4 g/m2
Blocking in the reel	Infrared thermometer at chill exit; reel store max-min	Web below 35 C at rewind, and taper the tension
Seal soft on an aged reel, fine on fresh web	Fresh versus aged ASTM F88 at the same settings; ASTM D1894 COF	Take wax and slip out; rotate stock and cool the store
Seal fails only over print or varnish	ASTM F88 on printed against unprinted area of the same web	Clear the seal land, or use a slip-free varnish there
Kit or Cobb60 short on coated board	Cut and weigh per pass, then the sheet over a light box	Split the weight into two dried passes
Pinholes and craters in the barrier	Look at the pan for a standing foam head	Slow the pump and submerge the return line
Viscosity climbing through the run	pH with a calibrated electrode, pan temperature, crosslinker log	Correct pH with stabiliser; add water only last

Functional CoatingsQuick reference

Quick reference

One page at the press

Symptom	Check this first	Change this first
Seals leak where product dust lands	Contaminated-seal test, 10 mg of their own product	Coat weight to the top of the range, fix dust extraction
Mottle or dry-back on absorbent board	Cobb60 on the uncoated base at three positions	Lower sealing pass first, then the barrier pass
Deposit building on the sealing jaw	Jaw face temperature against top of the window	Drop the jaw to mid-window; re-face the Teflon cold
Primer failing on metallised film	Look at the tape: clear film means the metal came away	Back to the film supplier, or cut primer to 0.3 to 0.8 g/m2
WVTR fails only after creasing	ASTM F1249 flat versus creased, same sheet	Widen the matrix; move to a more flexible grade
OTR poor in humid months	ASTM F1927 at the real storage RH; D3985 is the dry figure	Restore the moisture top coat over the oxygen layer
Seal strong one edge, weak the other	Coat weight at five cross-web positions; jaw profile	Correct the blade and chamber ends; repair jaw heaters
Pouch bursts at the filler, cold seal fine	Time the product drop against the jaw-open signal	Cool the seal, then set the jaw at the hot tack peak

Functional CoatingsQuick reference

Quick reference

One page at the press

Symptom	Check this first	Change this first
Grit, streaks and blinded filters	500 ml through a 100 micron mesh; drum date and history	Reject the drum; wash up the chamber and engraving

Functional CoatingsQuick reference

Test methods

The measurements this guide relies on

Measurement	Method	What it tells you, and the usual acceptance
Heat seal sample preparation	ASTM F2029	Defines how the seal under test was made. Reference condition here is flat Teflon-faced jaws, one side heated, 0.5 s dwell at 0.2 N/mm2, unless the customer's own line settings are being matched. Seal initiation temperature quoted without a dwell and a pressure is not a specification.
Seal strength	ASTM F88/F88M	15 mm strip at 300 mm/min, 23 C and 50 % RH, not less than 24 h after sealing. Typical acceptance: 350 to 900 g/15 mm for UniSeal-510PS, 600 to 1200 for 515PT, 1500 to 2500 for 530LK against a design floor of 1200, 500 to 1000 for 545LT, all on the stated construction and re-measured on the customer's own material before it goes into a specification.
Hot tack	ASTM F1921 Method B	Strength of the seal while still hot, read at 0.2 s delay. Typical 2 to 4 N/15 mm at the peak for UniSeal-530LK. It peaks and then falls with jaw temperature, which is why it is measured rather than inferred from cold seal strength.
Blocking	Written in-house method based on ASTM D1146 or ASTM D3354	Face to reverse, 24 h at the grade's stated temperature and 50 % RH under 10 kPa, then separated on a tensile tester at a stated rate. Report the separation force together with what is seen: lacquer transfer, print lift, audible pick. Standard grades are quoted at 50 C, UniSeal-545LT at 40 C. Attach the method to the specification, because a blocking figure without its method and its storage condition is not a specification.
Flow cup viscosity	ISO 2431, 4 mm orifice	Supply and pan viscosity at 25 C: heat-seal lacquers 22 to 30 s, grease and water barrier 25 to 40 s, oxygen base coat 30 to 45 s, moisture top coat 25 to 35 s. A DIN 53211 cup, the so-called DIN 4, is a different geometry and does not read the same seconds on the same material, so record which cup was used and never compare the two. Primers are quoted on Ford Cup B4 and must not be compared with either.
Water absorption, Cobb60	ISO 535	60 s contact, 23 C and 50 % RH, reported in g/m2, on the approval base board: UniBar-610GW at 6 to 8 g/m2 gives 8 to 15; UniBar-625MB at 8 to 12 g/m2 in two passes gives 3 to 8; UniBar-655HB gives 5 to 12. Uncoated kraft or board runs 25 to 40 for scale. Every figure in this table is on a stated base at a stated coat weight; it is an indication of what the coating can do, not a property of the coating, and the number that goes into a specification is the one measured on the customer's own board at the coat weight their machine lays down.
Grease resistance, kit rating	TAPPI T 559	3M kit reagents, 23 C and 50 % RH, scale 1 to 12, on the approval base board: UniBar-610GW gives kit 9 to 11 at 6 to 8 g/m2 and 11 to 12 at 10 to 12 g/m2 in two passes. It is a cold screening method; hot grease is checked separately at 60 C for 30 min on the customer's own base, and the specification figure is the one measured on that base.

Functional CoatingsTest methods

Test methods

The measurements this guide relies on

Measurement	Method	What it tells you, and the usual acceptance
Oxygen transmission rate	ASTM D3985 dry, ASTM F1927 at controlled humidity	Coulometric, 1 atm oxygen, cm3/m2.24h.bar. D3985 is the dry-gas method and gives the 0 % RH figure only; a humidity-conditioned number is run to F1927, which humidifies both carrier and test gas. UniBar-630OB at 2 to 4 g/m2 on 12 micron PET under the top coat: below 1 dry, 2 to 10 at 50 % RH, 20 to 80 at 80 % RH. Always quote temperature and both humidities with the number, because the polymer plasticises with water.
Water vapour transmission rate	ASTM F1249	Modulated infrared sensor on the finished coated board. UniBar-625MB at 8 to 12 g/m2 in two passes: 10 to 30 g/m2 in 24 h at 38 C and 90 % RH, or 4 to 12 at 23 C and 85 % RH, on the stated base board. The two conditions differ by a factor of two to three on the same sample, so the condition travels with the number.
Wetting tension	ISO 8296, or ASTM D2578 on polyethylene and polypropylene film	Substrate surface energy, measured on the reel about to run rather than on the certificate. ISO 8296 is the general film and sheeting method and is the correct citation for PET, metallised PET and BOPP; ASTM D2578 is scoped to polyethylene and polypropylene film. Treated film for water-based coating and primer work needs 38 to 42 mN/m or above. Dyne pens are a screening tool only and typically read 2 to 4 mN/m high against the inks.
Coefficient of friction	ASTM D1894	Static and kinetic friction of the coated face, used to follow slip additive arriving at the surface over reel age and to explain a reel that walks on the converting line. Quote the mating face, the sled load and the speed with the figure; a COF measured against steel is not the figure measured face to face.
Solvent resistance, MEK double rubs	ASTM D5402	Used on the UV LED primer to show the network has formed, not as an adhesion test. Rub under local extraction, away from ignition sources, in gloves and eye protection. Report the number of double rubs and the load; an aqueous coalescing film is not judged by this method.

Functional CoatingsTest methods

When the press-floor fixes have not worked

What to send us

300 mm of the full web width, unslit, from the reel that failed, with the reel number, the metre mark and the position in the run written on it; and the same again from a reel that ran well, because the comparison is what makes the sample useful.
300 mm of the uncoated base material from the same reel or pallet, plus the mill's or film supplier's certificate for it, including the extrusion date and the slip and antiblock package where the fault is a seal fault, since almost every barrier and adhesion figure belongs to the construction rather than to the coating.
A 500 g sample drawn from the pan at the moment of the fault, not from the drum, together with the drum batch number, the manufacturing date and the drum's own store history.
The coating log for that reel: cup seconds with the cup type and the sample temperature, ISO 3251 solids, pH, any crosslinker addition and the time it was made, line speed, tunnel length, tunnel zone set-points, measured web temperature at the tunnel exit and at the chill roll, anilox or cylinder specification with its last measured volume in cm3/m2, and the cut-and-weigh coat weights across the web.
The failed seals or failed packs themselves, unopened where possible, each marked with the jaw temperature, dwell, pressure and machine; plus photographs of the fault with a scale rule in frame.
The customer's own acceptance as written: which method, which condition, which number, and who signed it, because a WVTR at 38 C and 90 % RH and one at 23 C and 85 % RH are not the same requirement.
The date of coating and the date of the failure, with the reel store and filling hall temperature and humidity record for the period between them, which is the missing evidence in most blocking, most additive migration and most humidity-related barrier complaints.

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Functional CoatingsTechnical service