But many coatings have benefits that are more than skin deep, going beyond visual appeal. Many coatings consist of four components: a solvent (which may be water) to give a fluid consistency; a binder, which binds pigment particles and adheres to the substrate; pigments, which provide hiding, color and mechanical properties; and additives, which provide additional properties.
Some coatings are flame-retardant, meaning they have properties that let them absorb heat and reduce heat transfer while forming insulation pockets between the surface and the flame, melting into a glasslike consistency or producing nonflammable gases.
Other benefits and applications abound. Zinc primer coatings conduct electricity, providing a high degree of cathodic protection. Aluminum coatings are used to reflect light or retain heat. Powder-coated surfaces are extremely resistant to dents. The list goes on and on.
But one thing all coatings have in common is a need for resistance to impact. Accidents happen. Vacuum cleaner handles can scrape against a painted wall. Shopping carts are prone to bumping car fenders and doors. But these types of impact accidents do not have to lead to chips, cracks, dents and dings. This is where proper impact testing of coatings is so important.
Today's impact test instruments cannot only tell us how coatings can stand up to varying degrees of impact, but also how they withstand impact under a variety of environmental conditions such as sub-ambient winter cold and summer heat and humidity. In the past, unsophisticated "drop the ball on the painted plaque" tests produced questionable results. Although inexpensive (or perhaps because they are inexpensive), these types of testing were subjective and inefficient.
Today, coating manufacturers are turning to more sophisticated and reliable impact testing equipment. One such company is Red Spot Paint & Varnish Co., a leader in the production of ecologically sound, high-performance coatings for automotive plastics, as well as coatings for plastics in sports and consumer products. Headquartered in Evansville, IN, Red Spot prides itself on its new product development and related R&D. So it shouldn't be a surprise that they use the most advanced impact testing equipment.
Red Spot's Lab Manager Jeff Adler says, "We've found that the Dynatup impact test instrument from Instron gives us the accuracy and repeatability we need. Unlike equipment that we've used in the past, the Dynatup provides us with a computer analysis of the impact test, including the velocity and total energy of each impact event."
Testing equipment is used to test the mechanical properties and performance of various materials, components and
structures in a variety of environments. Coatings are just one of the many materials Instron systems test.
At Red Spot, the Dynatup machine allows the manufacturer to efficiently perform hundreds of impact tests. Red Spot is able to see how its coatings perform when bonded to a variety of different plastics and when used under a range of different conditions. In so doing, it can identify what raw materials work to decrease the brittleness of unpainted plastics, and thus which materials work best in its paint formulas.
The Dynatup tests impact properties of polymers, metals, composites as well as the paints and coatings used on these products. Unlike most testers, it captures, plots and analyzes the entire impact event. This means the system is able to determine important data such as the ductile-to-brittle transition point, ductility, incipient damage, max load and absorbed energy.
The machine helps Red Spot meet the most stringent industry standards. "We perform a test method per GM9904P," Adler says, "which provides us with information on the traits of a given coated plastic and the reasons for failure, whether it be ductile or brittle or whether it is unable to stand up to extremes in temperature and environment. For Ford Motor Co., we perform tests to meet ASTM D 3763, and we see a wide variety of impact retention changes. I have seen impact retention as low as 10% and as high as 200%."
Adler knows the dangers inherent to not using the most reliable impact testing equipment. "Because our customers count on us to predict how coatings perform, a lot is riding on our impact testing. With the Instron testers, we can be certain that our products meet the required specifications before they go out the door."
Thanks to today's impact test instrument, companies like Red Spot have a greater understanding of the real-world properties and characteristics of the coatings they manufacture. And vacuum cleaner handles, shopping carts, airborne pebbles and the like can have much less impact on the coated products we use everyday. c
For more information on testing equipment, contact Frank Lio, Instron, 100 Royall St., Canton, MA 02021; phone
800/564.8378; fax 781/575.5751; e-mail info firstname.lastname@example.org; visit www.instron.com.