Paint DurabilitySign Builder Illustrated Magazine

December 2007Article Reprint

Sign painters have longbeen an integral part of the sign industry.

The coatings they use provide finished signs

with dynamic colors, enhanced texture, and

outstanding visual appeal. With this in mind,

their paint selection is an important compo-

nent of the fabrication process.

Polyurethane coatings are among the high-

est-performing paint systems, and they’re

also the primary type of paint being used

within the sign industry . “Polyurethanes have

superior abrasion resistance, excellent chem-

ical resistance, and are highly resistant to UV

light degradation,” explains Donna Schaefer,

marketing manager at Matthews Paint

(www.matthewspaint.com). “They’re speci-

fied because of their excellent weathering

and their color and gloss retent ion.

Polyurethane chemistry is the industry stan-

dard—where graffiti resistance is a priority

in topcoat selection. Polyurethane coatings

retain their hard, durable finish and good-

looking appearance for years.”

Pa i n t sB y J e f f Wo o t e n

PaintDurability

2

Making sure one’s paint jobwill last for years to come.

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Sign painters have longbeen an integral part of the sign industry.

The coatings they use provide finished signs

with dynamic colors, enhanced texture, and

outstanding visual appeal. With this in mind,

their paint selection is an important compo-

nent of the fabrication process.

Polyurethane coatings are among the high-

est-performing paint systems, and they’re

also the primary type of paint being used

within the sign industry . “Polyurethanes have

superior abrasion resistance, excellent chem-

ical resistance, and are highly resistant to UV

light degradation,” explains Donna Schaefer,

marketing manager at Matthews Paint

(www.matthewspaint.com). “They’re speci-

fied because of their excellent weathering

and their color and gloss retent ion.

Polyurethane chemistry is the industry stan-

dard—where graffiti resistance is a priority

in topcoat selection. Polyurethane coatings

retain their hard, durable finish and good-

looking appearance for years.”

Pa i n t sB y J e f f Wo o t e n

PaintDurability

2

Making sure one’s paint jobwill last for years to come.

PH

OTO

CO

UR

TE

SY

OF

OF

AG

I/VIR

GIN

IA B

EA

CH

, VIR

GIN

IA.

Sign painters have longbeen an integral part of the sign industry.

The coatings they use provide finished signs

with dynamic colors, enhanced texture, and

outstanding visual appeal. With this in mind,

their paint selection is an important compo-

nent of the fabrication process.

Polyurethane coatings are among the high-

est-performing paint systems, and they’re

also the primary type of paint being used

within the sign industry . “Polyurethanes have

superior abrasion resistance, excellent chem-

ical resistance, and are highly resistant to UV

light degradation,” explains Donna Schaefer,

marketing manager at Matthews Paint

(www.matthewspaint.com). “They’re speci-

fied because of their excellent weathering

and their color and gloss retent ion.

Polyurethane chemistry is the industry stan-

dard—where graffiti resistance is a priority

in topcoat selection. Polyurethane coatings

retain their hard, durable finish and good-

looking appearance for years.”

Pa i n t sB y J e f f Wo o t e n

PaintDurability

2

Making sure one’s paint jobwill last for years to come.

PH

OTO

CO

UR

TE

SY

OF

OF

AG

I/VIR

GIN

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EA

CH

, VIR

GIN

IA.

durability: humidity, salt air, and tem-perature extremes, to name a few envi-ronmental examples.

It also helps to think of the future andconsider if durability will be an issuedown the road. If they believe this couldbe a potential problem, an investmenttoday in high-quality paint will forestallheadaches later on.

According to paint experts, this is anideal opportunity where spending theextra money will prove to be worth theinvestment.

Jeff Damm, new product and color

specialist at Matthews Paint, explainsthat paint durability is dependent on thestrength of the coating. “The three mostimportant factors behind the cause ofsurface coating breakdown are a com-bination of UV light, heat, and mois-ture,” Damm explains.

To protect against breakdown, it’simportant to consider the followingitems:

Binder. There are three basic com-ponents found in paint: the binder (thebackbone of paint), the pigment (which

provides the color), and the solvent(which provides fluidity). Let’s discussthe binder.

There are different qualities of binders(acrylics, alkyds, lacquers, etc.), but typ-ical binders for durable coatings are(listed in order of durability and, inci-dentally, cost): Polyvinyl fluorides (flu-oropolymer coatings), acrylic urethanes,and pure acrylics.

Urethanes are the coating of choicein the signage industry because of theirversatility, their high performance char-acteristics, and their ease of use. Theyalso sport a greater range of color thanpolyvinyl fluorides.

As far as durability, a sign profes-sional needs to be aware of the possi-bility of the paint chalking. “Chalkingoccurs when the binder or pigmentbreaks down,” says Steve Sawar, tech-nical director at Matthews Paint.

Pigments. There are many grades ofpigments, some more durable than oth-ers. High-end paint systems use onlytop-grade pigments that are light-fast.

“The pigments used, for example, ininterior flat paint are different than whatwould be used in automotive-style coat-ings,” comments Damm. “The pigmentsthat we—and all high-end paint manu-facturers—use are ‘automotive-grade,’which means they possess the highestdurability as that type of pigment canhave.”

Damm also notes that lower-end coat-ings use lower-end pigments, whichleads to chalking and color differencemuch sooner than you’d experience witha high-end paint.

(Note: What most people describe asfading results not from the pigment itself,but instead from when the binder resinbreaks down and chalks. You lose thegloss through the binder breaking down.)

Surface properties. The surface ofa coating can affect durability. For exam-ple, a less permeable film will degradefaster than high-gloss coatings.“Sincethey’re not as ‘tight’ as a full-gloss fin-ish, they’re more easily invaded by water,moisture, etc.,” comments Sawar.

Film thickness also comes into playhere. “Low film thickness is often thecause of paint failures in urethanes,” saysSawar, “as the proper film thickness ofthe primer and the topcoat is critical topaint system durability.”

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Sign painters want their finished workto be visibly appealing for as long aspossible. Some frequently asked ques-tions regarding paint durability and per-formance include:

� How long will the paint last?

�What happens if somebody van-dalizes the finish?

� How does it weather?

�Will it stick to the primer I used?

� Can I afford this paint?

�How do you clean a painted sign?

“Ultimately sign makers and end-users want a long-lasting, cleanable, anddurable-painted coating,” says JanScheske, customer service/inside salesmanager at Matthews Paint. “Becausethe sign is their advertising tool and pro-motes the image of a company, userswant it to look as good as possible foras long as possible.”

To make certain that their signage willlast as long as possible, sign paintersneed to consider a variety of factors thatcan affect a paint’s performance and

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to make certain that the painted signhas the appropriate amount of time forcuring, so that it hardens to its fullestbefore being handled, packaged, andshipped.”

However there’s a difference in beingfully dry to the touch and being cured.“Typically urethanes can take betweenfive to seven days to reach full cure,unless the sign is being baked or accel-erated,” says Sawar. “One of the reasonsthe industry has come up with accelera-tors is to speed up the polimerizationprocess (the paint/catalyst reaction). Forexample, using an accelerator enablesthe sign builder to apply vinyl in hoursrather than days.”

Sawar also points out that packing-related problems can occur if the paintused on the sign isn’t allowed time to

fully cure. “If you wrap your sign withbubble wrap or plastic film too soon,then when it comes time to open up thepackage, the packing might end up stuckto the face of the paint or it might leavetracks,” he says.

Temperature also plays a crucial rolein a urethane’s ability to cross-link. Forexample, painting in a cold environment(55°F or lower) will stop the coatingfrom cross-linking, which will in turncause irreversible damage to the film’sdesirable properties. Once the cross-link-ing process has stopped, it will neverresume.

(Note: When curing, it’s also impor-tant to store the painted signage in cleanareas above 55°F and to not expose it tomoisture.)

Clear coats. Clear coats are alwaysa good idea if the ultimate in longevityis what the sign builder is looking for;a clear coat will add an additional layerof protection.

A key point with clear coats is thatthe higher the gloss, the better it’s goingto hold up due to not having inert mate-rials that tend to compromise filmintegrity.

Finally Scheske advises sign paintersto call their paint manufacturers withany questions they might have about theproduct. It’s very important to know thetechnical requirements before starting aproject. Finding out these answersupfront will help to ensure a long-lastingand high-quality paint job today and theforseeable future. b

There are a variety of testing methods employedby manufacturers to make certain that urethanepaints will be able to last in an environment or geo-graphic location for as long as possible. These spe-cific tests include:

1.Natural weathering test. This is a real world testof paint durability, and it’s usually conducted at

test farms in Arizona, Florida, and other places thatexperience high sunlight intensity and/or significantheat and humidity. “In this type of test, you paint thesubstrate and then leave it out in the sun,” says SteveSawar, technical director at Matthews Paint. “Forexample, in the state of Florida, a standard test wouldbe five years.”

(Note: This is considered to be the most reliable ofpaint testing methods.

2.Accelerated weathering test. This procedureexposes coatings in a QUV cabinet to a combi-

nation of UV bombardment by special fluorescentlight, moisture, and heat. Cabinets can be set up forfour-hour cycles (four hours of light exposure andfour hours of heat and humidity or any number ofeven hours.) This method is good for quick head-to-head evaluation of coating variations or competitiveproducts, but it can’t be equated with “x” number ofyears natural exposure in the real world.

3.Carbon arc chamber exposure. Similar to theQUV cabinet but using a carbon arc light and

lacking the moisture/condensation cycle. Since itdoesn’t contain some of the wavelengths that fluores-cent bulbs do, it’s a more natural accelerated weath-ering test.

4.Salt spray (fog chamber). This testing method isconducted in a chamber and uses salt fog. “Salt

spray is an accelerated corrosive environmentintended to check how corrosion-resistant the coat-ing system is,” says Sawar.

There are also a couple of tools that are used innatural and accelerated weathering tests:

Spectrophotometer. This is used to measure colorshift. The unit of measure is Delta E (total color differ-ence). Some of the mathematical models used are:CIE Lab, CIE Luv, Hunter Lab, FMCII, and CMC. “[DeltaE] turns color into numbers,” explains Jeff Damm,new product and color specialist at Matthews Paint.“You can assign numbers to the color shift induced.For example, if there was five delta E differencebetween a control panel and a weathered panel, itcan be used as a basis for comparison of differentformulations.”

Glossmeter. This is used to measure the surfacecondition (gloss) of paint films, there are three types:60-degree glossmeter (general purpose instrument),20-degree glossmeter (used to measure high-glossfinishes), and 85-degree glossmeter (used to measurevery low gloss (matte) finishes).

“You simply beam down a light at a certain angleand then a sensor reads how much of that is reflectedoff that same angle,” explains Damm. “The moretextured a surface is, the more light that’s going to bescattered and the less light that’s going to bereceived by the receptor. In exposure testing, gloss-meters are used to calculate gloss loss by comparingreadings of control and exposed panels.”

Testing Coating Durability

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Proper mixing. Two-part (2K) ure-thanes are dependent on the proper ratioof paint and catalyst. Improper mixingcauses the loss of desirable properties.Without a catalyst, a 2K urethane simplywill not cross-link (i.e., the build-up oflong-chain polymers that are highlyresistant to sunlight and chalking). “It’smore related to the proper volumes thatare being mixed,” explains Damm.

Surface preparation and primers.Proper substrate preparation—sanding,cleaning, etc.—is very important; so tooare the primers that are being used. Theprimer acts to improve the substrate’ssurface and gives the topcoat greateradhesion capabilities. Without a properprimer, even the best surface coatingwon’t perform well.

“The appropriate primer depends onwhat type of substrate you’re paintingonto,” says Sawar. “When you’re talkingabout metals, most companies have a vari-ety of primers you can use—dependingon the corrosion resistance required andthe level of filling capability needed, toname a few.

“There are a variety of primers avail-able for almost any type of substrate—including etching primers, epoxy primers,and urethane primers. It’s important toensure that you use the correct primer forthe job you’re doing.”

Clean equipment. Cleanliness is anessential component of the successfulpaint job. Sawar points out that not onlydo sign painters need to always useclean tools when applying primers andcoatings, they also need to make cer-tain that the surface of the substrate isclean. “This will assist in the ultimatequality of what’s being sprayed,”remarks Sawar.

According to Sawar, there are clean-ers available in the marketplace that aredesigned to prepare and clean your sprayequipment and the substrate you’reusing.

Cure time. It’s important to followthe paint manufacturer’s directions interms of cleaning, application, and theamount of time it takes to go from wetto fully cured and developed. “In ourindustry, turnaround time is critical,”says Scheske. “Sign professionals aretrying to paint and get the productshipped off quickly. However one needs

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Matthews Paint offers everything you need to transform your idea into colorful reality.

Let Matthews Paint enhance and preserve your image.

Call for your freeProduct Overview Guide.

1.800.323.6593www.matthewspaint.com

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