UV Light Resistance Testing for Polyurethane and Vinyl Materials

An increasingly important performance value for coated fabrics is ultraviolet (UV) light resistance. It is known that polyurethane and vinyl materials used for both interior and exterior applications are subject to photo-degradation when exposed to ultraviolet light. Photo-degradation is a process whereby the polymer chains in the product break down due to exposure to UV radiation. The UV light, which makes up about 10% of sunlight, is electromagnetic radiation with a wavelength shorter than visible light but longer than x-rays. 

UV radiation from sunlight can be ameliorated or prevented by adding anti-UV chemicals to the polymer when mixing the ingredients for a product. UV stabilizers in plastics usually act by absorbing the UV radiation, and dissipating the energy as low level heat. The chemicals used are similar to those used in sunscreen cosmetic products, which protect skin from UV light.

In order to test the UV stability of polymers several weathering test methods have been developed using artificial light sources to provide accelerated test procedures. These test methods are used to predict the UV stability of a product over a number of years.

Two of the accepted UV stability tests in the coated fabrics industry include AATCC Test Method 16-2004 -- Colorfastness to Light, and ASTM D4329-05 -- Standard Practice for Fluorescent UV Exposure of Plastics. These tests simulate weathering and realistically reproduce the physical damage caused by short-wave UV radiation by exposing materials to alternating cycles of UV light (using special fluorescent UV lamps) and moisture at controlled, elevated temperatures. In a few days or weeks, the UV test machine can reproduce the damage that occurs over months or years naturally.

Samples of the textile material to be tested are exposed to a UV light source under specified conditions. The colorfastness to light of the specimen is evaluated by comparison of the color change of the exposed portion of the test specimen to the unexposed original material. The change in color can be measured by a spectrophotometer. 

The upholstery industry standard for UV resistance test is at least 40 hours with no color change. High performance faux leather upholstery for hospitality, contract and healthcare applications can pass 200/+ hours with no color change.