Modern high-solids, reactive
finishes require some knowledge of what’s happening in the mixing room and in the gun. combine this with the painter’s skill, and you’ve got the perfect chemistry.
It has never been proved that Henry Ford said, “You can have any color you want, as long as it’s black,” in reference to his ultra-popular Model T Ford, but the memorable quotation has become part of automotive industry mythology. A few years after Ford allegedly made that comment, nitrocellulose lacquer, the first sprayable automotive finish, was introduced and the monochromatic automobile landscape was changed forever. In its place came a bright, multi-hued palette from which car owners now can choose virtually any color imaginable.Throughout the years, automotive finishes have come a long way from those first nitrocellulose lacquers. Alkyd enamels, which needed no compounding, came along in the 1930s. At the same time, metallics, formulated by adding materials such as bronze powders, became popular. These “glamour” finishes reflected light. Acrylic lacquers, with better gloss and color retention than alkyd enamels, were introduced in the mid-‘50s. In the 1970s came acrylic enamels and urethanes, which, like alkyds, required no compounding and offered the added benefits of fast dry and increased durability. Polyurethanes—the ultimate in durability and chemical resistance—soon followed, and promptly became the favorite of the heavy-duty truck industry.
Pearls also gained popularity in the 1970s and began to supplant some metallics. Pearls gave cars a cleaner look by reflecting the most prominent color in the paint back in the direction of the light source. Today, pearls allow car makers to offer colors that are cleaner and brighter, with more sparkle than metallic flakes.Finishes were almost exclusively single-stage until the 1980s. Then things got slightly more complicated for refinishers. Clearcoats, which delivered increased gloss and durability, became popular with auto manufacturers—so popular, in fact, that today single-stage finishes are almost obsolete. Next came two-component, or activated products—paint manufacturers developed various additives designed to enhance dry time, durability, chip resistance, flexibility and gloss. By the late 1980s, health and environmental regulations spurred the development of high-solids, low-VOC finishes, and, in Europe, waterborne coatings.It’s in the Can
While automotive finishes have become more complex throughout the years, the basic content of a can of paint has remained essentially the same. Paint typically consists of three—and oftentimes four—components, which include the following:Pigment/metallic or pearl flake
Binder
Solvent
Additives
Pigment is the ingredient in paint that imparts color. It does this by reflecting and absorbing light rays. A blue pigment absorbs all the light rays except blue, which it reflects. The same goes for red. The white pigment, however, reflects all the colors of the spectrum. And a black pigment absorbs all the colors of the spectrum.In addition to color, pigments impart durability, corrosion protection and hiding. They may also improve strength and adhesion, change gloss, and modify flow and application properties. The most costly of the components, pigments are made of such elements as aluminum and mica.The size and shape of pigment particles are important. Pigment particle size affects hiding ability, while pigment shape affects strength. Pigment particles may be nearly spherical, rod- or plate-like. Rod-shaped particles, for example, reinforce paint film like iron bars in concrete. Pearls reflect color while metallics reflect light. The binder, or film former, holds the pigment in liquid form, makes it durable and gives it the ability to stick to a surface. The binder is the backbone of paint. It’s generally made of a natural resin—rosin, for example—drying oils such as linseed or cottonseed, or a man-made plastic (methyl methacrylate, polyurethane, polystyrene, polyvinyl chloride, etc.). The binder dictates the type of paint to be produced because it contains the drying mechanism. The binder is usually modified with plasticizers, cross linkers or additives and catalysts. These improve properties such as durability, adhesion, corrosion resistance, mar resistance and flexibility. Lacquers use long chain resins in the binder and rely on entanglement of the resin chains to provide film integrity. These systems are not cross-linked. Today’s refinish systems use a cross-linked binder system in which the binder resins react with an activator to provide a tougher, more durable film than the older lacquer technologies.The third component of paint is solvent, or the transfer medium. Solvent reduces the binder and transfers the pigment and binder through the spray gun to the surface that is being painted. Many solvents are derived from crude oil or hydrocarbons. Others are made of ketones, esters, alcohols and water.When used with enamel, the solvent is called a reducer. With lacquer, it’s called thinner.Properties affected by solvents include viscosity, odor, package stability, flow, appearance, color, toxicity, VOC content and popping.In most automotive finishes, there are other components that can be lumped into a fourth category: Additives. They might make up only a small percentage of a finish, but they have a significant influence on its physical and chemical properties. Additives can speed curing, prevent wrinkling or blushing, or improve chemical resistance or gloss. Once these ingredients are combined, they are then subject to the inconsistencies of both the automaker’s production line and the refinish shop. Both sometimes conspire to change the basic chemistry of a paint color, and, therefore, the appearance of the finish.At the OEM level, two cars painted with the same color can appear quite different when they roll off the assembly line. That’s because they’re often painted in two different plants, under different conditions and with two different paint manufacturers’ products. Even when painted at the same plant, a color on a vehicle that comes off the production line in the morning can look lighter than that same color on a car that rolls out late in the day. That’s because the robotic equipment that applies OEM finishes keeps the paint in constant motion. While this motion ensures proper mixing and metal flake distribution, it can also cause the flakes to bend and break as they collide. The result? The paint appears darker than the standard color because the smaller bent or broken flakes reflect less light.Painter/Chemist?
Given the indignities that paint is subject to at the OEM level, it’s imperative that the autobody shop does nothing further to change the chemistry of refinish coatings. This leads to the question: How much chemistry does a painter need to know to produce a good color match? Probably not much more than the information outlined above. But there are a few things that he or she should keep in mind.“Most systems are chemically reactive,” says Jay Kaiser, product platform manager for DuPont Finishes. “So the painter needs to ask a question such as: What is the shelf life? What is the pot life of the chemistry in question? Is the ready-to-spray mixture the right viscosity?”The temperature in which the finish is cured can have a profound effect on results, says Vince Goldman, R&D manager for Transtar Autobody Technologies. “Manufacturers will recommend longer cure times at cooler temperatures, so the refinisher will need to be more patient before sanding a primer and before buffing a clearcoat. He or she must follow these directions carefully. If one rushes in cooler temperatures, problems like sand scratching are sure to show up. Conversely, in the warmer months, it may be necessary to use additives to ensure optimum clearcoat appearance.”Mixing accuracy is critical, of course, and it’s made even more so by the characteristics of modern high-solids finishes. Brent Wallace, a product manager for BASF’s R-M and Limco Brands, says “Many of today’s paint lines are more highly pigmented, to impove hiding, than those in the past. This means that even small overpours can affect a formula. That’s why it’s important for shops to use software that can automatically recalculate formulas if an overpour occurs.”Whole Lotta Shakin’
Because most toners employ high pigment loads to achieve quick opacity, it’s important that the toners and mixing bank are properly maintained, says Mark Rapson, brand manager for PPG Collision Refinish. “Keep the toners regularly agitated according to the manufacturer’s recommendation,” he advises. “Improper maintenance of the mixing scheme is the No. 1 reason for poor or inconsistent color match.”Chemistry aside, most experts agree that a painter’s skill and experience are usually the most important factors in achieving an accurate match. “Over the years, the best painters come to rely on their ability to adjust and move color based on a labor-intensive process of spray-out, adjust and tint,” says Alan Craighead, manager of technical services for Akzo Nobel.“We work with customers to streamline that process, and help painters move from being applicators to artisans.”
Kent Gardner, president of Matrix System Automotive Finishes, says technology has not changed the color-matching process to any great extent. “The painter still needs the skill and talent to tint and blend colors to match OEM finishes that vary from standards,” he says.As for the immediate future, painters should be prepared to see more ultraviolet cured undercoats and topcoats. “Clearly the most exciting advance in auto refinish coatings, and the one that has had the greatest impact on the repair process, is the introduction of UV cured undercoats,” Rapson says. “UV-cured primers reduce the repair and prep time from the point of application to point of topcoat by as much as 80 percent.” And don’t forget UV-cured clearcoats. “These are the next chemistry that will be adopted in the body shop as the UV curing technology expands,” says Tim Herrington, color and compliance manager for Valspar. “These products will speed the repair process and reduce the cost for utilities because gas-fired or electrically heated booths will not be required to cure the coatings.”Darlene Eilenberger, BASF brand marketing manager, offers a cautionary note. “There are still issues that need to be worked out with regard to safety, light sources and other equipment that is designed for use in body shops,” she says. “Once these issues are resolved, UV coatings will increasingly become a factor in the body shop because of the potentially dramatic productivity improvements they offer.”Another trend that painters can expect is special effect colors, such as Xirallic pigments, which have a pearl-like appearance head on, with a brighter side tone versus the muddy side tone of a pearl. Another popular special effect, offered by a handful of OEMs, is a finish that changes color depending on the viewing angle. “The number of OEM vehicles painted with special effect colors increases each year,” says Bob Pittenger, training manager for Spies Hecker. “As this trend continues, painters will need to be knowledgeable and properly trained in handling these colors, as reducer selection and gun technique become more critical.” Environmental considerations will continue to have an effect on paint chemistry, according to DuPont’s Kaiser. “Regulatory changes will increasingly force the elimination of hazardous materials like chromium, HAPS containing solvents, and eventually higher solids levels,” he says. “As products use new solvent blends and move to higher solids, the need for a highly skilled painter who can adapt to new products will be more important.”Whither Waterborne?
No discussion of the future of refinish paint would be complete without mentioning waterborne finishes. These environmentally-friendly products account for more than 30 percent of the market in Europe, and they’ve been nipping at the edges of the U.S. refinish industry for years. PPG’s Rapson confirms that they are “the future.”“Outside North America, water is growing at double digits annually,” he says. “If you look at any trend within the industry, you find North America generally follows five to 10 years behind Europe. In North America, waterborne got a poor start early on, based on the technology introduced at the time, but over the last 10 years there have been significant advances in waterborne basecoat.”Several manufacturers are poised and ready if and when the water spigot is turned on in the U.S. And that appears to be inevitable, according to some industry observers.“There are 99 OEM plants in North America, 33 of which apply waterborne basecoat to production vehicles,” says Petra Schroeder, Standox product manager. “This number is expected to double in the next five years. From the OEMs, the use of waterborne finishes moves to their vehicle processing centers, where manufacturers like Mercedes-Benz, BMW and Porsche use predominately waterborne technology. This path is expected to continue downward from the vehicle processing centers to the body shops, where the repair will be more consistent if the repair materials reflect the properties of the original finish.” Kaiser believes that only larger, better-equipped shops will be able to use waterborne effectively. “Water’s key attribute is appearance and the ability to paint relatively quickly,” he explains. “Then it’s a question of whether or not you are facilitized to dry it. I’m not sure I’d want it in a small shop with a relatively low airflow booth on a humid day.”Matrix’s Gardner agrees. “If the U.S. government mandates much lower VOC basecoats, water will be the only way to go,” he says. “[But] many small-to mid-size shops may have problems with water systems because of the atmospheric controls and equipment required to spray them effectively.”Valspar’s Herrington remains skeptical. “Waterborne products, beyond waterborne cleaners, will not be widely adopted in the refinish market unless their use is required by governmental legislation,” he says. Who knows? The collision repair paint of the future may be something entirely different, as indicated by BASF’s Eilenberger, “There is talk in the industry of paint films. If paint films become marketable, their impact on the market would be dramatic. For one thing, VOCs would no longer be an issue.”
It has never been proved that Henry Ford said, “You can have any color you want, as long as it’s black,” in reference to his ultra-popular Model T Ford, but the memorable quotation has become part of automotive industry mythology. A few years after Ford allegedly made that comment, nitrocellulose lacquer, the first sprayable automotive finish, was introduced and the monochromatic automobile landscape was changed forever. In its place came a bright, multi-hued palette from which car owners now can choose virtually any color imaginable.Throughout the years, automotive finishes have come a long way from those first nitrocellulose lacquers. Alkyd enamels, which needed no compounding, came along in the 1930s. At the same time, metallics, formulated by adding materials such as bronze powders, became popular. These “glamour” finishes reflected light. Acrylic lacquers, with better gloss and color retention than alkyd enamels, were introduced in the mid-‘50s. In the 1970s came acrylic enamels and urethanes, which, like alkyds, required no compounding and offered the added benefits of fast dry and increased durability. Polyurethanes—the ultimate in durability and chemical resistance—soon followed, and promptly became the favorite of the heavy-duty truck industry.
Pearls also gained popularity in the 1970s and began to supplant some metallics. Pearls gave cars a cleaner look by reflecting the most prominent color in the paint back in the direction of the light source. Today, pearls allow car makers to offer colors that are cleaner and brighter, with more sparkle than metallic flakes.Finishes were almost exclusively single-stage until the 1980s. Then things got slightly more complicated for refinishers. Clearcoats, which delivered increased gloss and durability, became popular with auto manufacturers—so popular, in fact, that today single-stage finishes are almost obsolete. Next came two-component, or activated products—paint manufacturers developed various additives designed to enhance dry time, durability, chip resistance, flexibility and gloss. By the late 1980s, health and environmental regulations spurred the development of high-solids, low-VOC finishes, and, in Europe, waterborne coatings.It’s in the Can
While automotive finishes have become more complex throughout the years, the basic content of a can of paint has remained essentially the same. Paint typically consists of three—and oftentimes four—components, which include the following:Pigment/metallic or pearl flake
Binder
Solvent
Additives
Pigment is the ingredient in paint that imparts color. It does this by reflecting and absorbing light rays. A blue pigment absorbs all the light rays except blue, which it reflects. The same goes for red. The white pigment, however, reflects all the colors of the spectrum. And a black pigment absorbs all the colors of the spectrum.In addition to color, pigments impart durability, corrosion protection and hiding. They may also improve strength and adhesion, change gloss, and modify flow and application properties. The most costly of the components, pigments are made of such elements as aluminum and mica.The size and shape of pigment particles are important. Pigment particle size affects hiding ability, while pigment shape affects strength. Pigment particles may be nearly spherical, rod- or plate-like. Rod-shaped particles, for example, reinforce paint film like iron bars in concrete. Pearls reflect color while metallics reflect light. The binder, or film former, holds the pigment in liquid form, makes it durable and gives it the ability to stick to a surface. The binder is the backbone of paint. It’s generally made of a natural resin—rosin, for example—drying oils such as linseed or cottonseed, or a man-made plastic (methyl methacrylate, polyurethane, polystyrene, polyvinyl chloride, etc.). The binder dictates the type of paint to be produced because it contains the drying mechanism. The binder is usually modified with plasticizers, cross linkers or additives and catalysts. These improve properties such as durability, adhesion, corrosion resistance, mar resistance and flexibility. Lacquers use long chain resins in the binder and rely on entanglement of the resin chains to provide film integrity. These systems are not cross-linked. Today’s refinish systems use a cross-linked binder system in which the binder resins react with an activator to provide a tougher, more durable film than the older lacquer technologies.The third component of paint is solvent, or the transfer medium. Solvent reduces the binder and transfers the pigment and binder through the spray gun to the surface that is being painted. Many solvents are derived from crude oil or hydrocarbons. Others are made of ketones, esters, alcohols and water.When used with enamel, the solvent is called a reducer. With lacquer, it’s called thinner.Properties affected by solvents include viscosity, odor, package stability, flow, appearance, color, toxicity, VOC content and popping.In most automotive finishes, there are other components that can be lumped into a fourth category: Additives. They might make up only a small percentage of a finish, but they have a significant influence on its physical and chemical properties. Additives can speed curing, prevent wrinkling or blushing, or improve chemical resistance or gloss. Once these ingredients are combined, they are then subject to the inconsistencies of both the automaker’s production line and the refinish shop. Both sometimes conspire to change the basic chemistry of a paint color, and, therefore, the appearance of the finish.At the OEM level, two cars painted with the same color can appear quite different when they roll off the assembly line. That’s because they’re often painted in two different plants, under different conditions and with two different paint manufacturers’ products. Even when painted at the same plant, a color on a vehicle that comes off the production line in the morning can look lighter than that same color on a car that rolls out late in the day. That’s because the robotic equipment that applies OEM finishes keeps the paint in constant motion. While this motion ensures proper mixing and metal flake distribution, it can also cause the flakes to bend and break as they collide. The result? The paint appears darker than the standard color because the smaller bent or broken flakes reflect less light.Painter/Chemist?
Given the indignities that paint is subject to at the OEM level, it’s imperative that the autobody shop does nothing further to change the chemistry of refinish coatings. This leads to the question: How much chemistry does a painter need to know to produce a good color match? Probably not much more than the information outlined above. But there are a few things that he or she should keep in mind.“Most systems are chemically reactive,” says Jay Kaiser, product platform manager for DuPont Finishes. “So the painter needs to ask a question such as: What is the shelf life? What is the pot life of the chemistry in question? Is the ready-to-spray mixture the right viscosity?”The temperature in which the finish is cured can have a profound effect on results, says Vince Goldman, R&D manager for Transtar Autobody Technologies. “Manufacturers will recommend longer cure times at cooler temperatures, so the refinisher will need to be more patient before sanding a primer and before buffing a clearcoat. He or she must follow these directions carefully. If one rushes in cooler temperatures, problems like sand scratching are sure to show up. Conversely, in the warmer months, it may be necessary to use additives to ensure optimum clearcoat appearance.”Mixing accuracy is critical, of course, and it’s made even more so by the characteristics of modern high-solids finishes. Brent Wallace, a product manager for BASF’s R-M and Limco Brands, says “Many of today’s paint lines are more highly pigmented, to impove hiding, than those in the past. This means that even small overpours can affect a formula. That’s why it’s important for shops to use software that can automatically recalculate formulas if an overpour occurs.”Whole Lotta Shakin’
Because most toners employ high pigment loads to achieve quick opacity, it’s important that the toners and mixing bank are properly maintained, says Mark Rapson, brand manager for PPG Collision Refinish. “Keep the toners regularly agitated according to the manufacturer’s recommendation,” he advises. “Improper maintenance of the mixing scheme is the No. 1 reason for poor or inconsistent color match.”Chemistry aside, most experts agree that a painter’s skill and experience are usually the most important factors in achieving an accurate match. “Over the years, the best painters come to rely on their ability to adjust and move color based on a labor-intensive process of spray-out, adjust and tint,” says Alan Craighead, manager of technical services for Akzo Nobel.“We work with customers to streamline that process, and help painters move from being applicators to artisans.”
Kent Gardner, president of Matrix System Automotive Finishes, says technology has not changed the color-matching process to any great extent. “The painter still needs the skill and talent to tint and blend colors to match OEM finishes that vary from standards,” he says.As for the immediate future, painters should be prepared to see more ultraviolet cured undercoats and topcoats. “Clearly the most exciting advance in auto refinish coatings, and the one that has had the greatest impact on the repair process, is the introduction of UV cured undercoats,” Rapson says. “UV-cured primers reduce the repair and prep time from the point of application to point of topcoat by as much as 80 percent.” And don’t forget UV-cured clearcoats. “These are the next chemistry that will be adopted in the body shop as the UV curing technology expands,” says Tim Herrington, color and compliance manager for Valspar. “These products will speed the repair process and reduce the cost for utilities because gas-fired or electrically heated booths will not be required to cure the coatings.”Darlene Eilenberger, BASF brand marketing manager, offers a cautionary note. “There are still issues that need to be worked out with regard to safety, light sources and other equipment that is designed for use in body shops,” she says. “Once these issues are resolved, UV coatings will increasingly become a factor in the body shop because of the potentially dramatic productivity improvements they offer.”Another trend that painters can expect is special effect colors, such as Xirallic pigments, which have a pearl-like appearance head on, with a brighter side tone versus the muddy side tone of a pearl. Another popular special effect, offered by a handful of OEMs, is a finish that changes color depending on the viewing angle. “The number of OEM vehicles painted with special effect colors increases each year,” says Bob Pittenger, training manager for Spies Hecker. “As this trend continues, painters will need to be knowledgeable and properly trained in handling these colors, as reducer selection and gun technique become more critical.” Environmental considerations will continue to have an effect on paint chemistry, according to DuPont’s Kaiser. “Regulatory changes will increasingly force the elimination of hazardous materials like chromium, HAPS containing solvents, and eventually higher solids levels,” he says. “As products use new solvent blends and move to higher solids, the need for a highly skilled painter who can adapt to new products will be more important.”Whither Waterborne?
No discussion of the future of refinish paint would be complete without mentioning waterborne finishes. These environmentally-friendly products account for more than 30 percent of the market in Europe, and they’ve been nipping at the edges of the U.S. refinish industry for years. PPG’s Rapson confirms that they are “the future.”“Outside North America, water is growing at double digits annually,” he says. “If you look at any trend within the industry, you find North America generally follows five to 10 years behind Europe. In North America, waterborne got a poor start early on, based on the technology introduced at the time, but over the last 10 years there have been significant advances in waterborne basecoat.”Several manufacturers are poised and ready if and when the water spigot is turned on in the U.S. And that appears to be inevitable, according to some industry observers.“There are 99 OEM plants in North America, 33 of which apply waterborne basecoat to production vehicles,” says Petra Schroeder, Standox product manager. “This number is expected to double in the next five years. From the OEMs, the use of waterborne finishes moves to their vehicle processing centers, where manufacturers like Mercedes-Benz, BMW and Porsche use predominately waterborne technology. This path is expected to continue downward from the vehicle processing centers to the body shops, where the repair will be more consistent if the repair materials reflect the properties of the original finish.” Kaiser believes that only larger, better-equipped shops will be able to use waterborne effectively. “Water’s key attribute is appearance and the ability to paint relatively quickly,” he explains. “Then it’s a question of whether or not you are facilitized to dry it. I’m not sure I’d want it in a small shop with a relatively low airflow booth on a humid day.”Matrix’s Gardner agrees. “If the U.S. government mandates much lower VOC basecoats, water will be the only way to go,” he says. “[But] many small-to mid-size shops may have problems with water systems because of the atmospheric controls and equipment required to spray them effectively.”Valspar’s Herrington remains skeptical. “Waterborne products, beyond waterborne cleaners, will not be widely adopted in the refinish market unless their use is required by governmental legislation,” he says. Who knows? The collision repair paint of the future may be something entirely different, as indicated by BASF’s Eilenberger, “There is talk in the industry of paint films. If paint films become marketable, their impact on the market would be dramatic. For one thing, VOCs would no longer be an issue.”
