Ultraviolet Resistance of Engineering Plastics
There are some polymers that are susceptible to attack form sunlight, in particular, the ultraviolet segment of the spectrum. When ultraviolet attack occurs the material may have a color shift, become chalky on its surface, and/or crack. There are a number of methods to reduce this problem. The addition of carbon black to the polymer will usually absorb most UV radiation. Chemical inhibitors are available for certain plastics, which improve the UV resistance. Paint and silicone coatings can also be used to completely cover exposed surfaces to sunlight (UV radiation). Additionally, there are several polymers on the market that are inherently UV resistant as well.
Acetal Homopolymer, Copolymer (polyozymethylene, POM)
Unmodified acetal resin will degrade over time upon exposure to sunlight. The material can crack, embrittle, and develop a chalky appearance. Pigmented and chemically modified formulations are available including Delrin® 107 acetal and Delrin® 507. DuPont has developed 20 year exposure data on these materials.
Nylon (all types)
Unpigmented resins will degrade upon exposure to sunlight evidenced by discoloration and embrittlement. Formulations containing carbon black particles provide the best UV stability.
Thermoplastic polyurethane exhibits good weathering characteristics. Upon exposure to UV radiation it does experience a color shift, however there is a minimal change in mechanical properties.
Unmodified polycarbonate resins (Hydex® 4301, Lexan®, Makrolon®) will degrade upon exposure to sunlight. Polycarbonate will yellow and become hazy after 1 year of exposure. UV resistant grades are available.
Polybutylene terephthalate (PBT) (also known as Hydex® 4101, Valox®, Celanex®, Ultraform®) is “inherently” UV resistant. Supplier data indicates that there is little degradation in mechanical properties after several years of exposure. Black pigmented resins have better property retention.
Polyetherimide (Ultem®) is inherently resistant to ultraviolet radiation. After 1000 hrs. of exposure, no measurable change with tensile strength.
ABS is not suitable for outdoor applications because of its poor UV resistance. Current UV stabilized grades refer only to color fastness not mechanical property retention.
Polysufone (Udel®) will experience some degradation upon exposure to sunlight. Black pigmented formulations are recommended for improved performance.
E = Excellent UV resistance
F = Fair UV resistance
U = Unacceptable UV resistance
Delrin® is a registered trademark of E. I. DuPont de Nemours Co., Inc.
Celanex and Celcon® is a registered trademark of Ticona – Division of Hoechst Group.
Ultraform® is a registered trademark of BASF Corporation.
Lexan® and Ultem® are registered trademarks of General Electric Company.
Udel® is a registered trademark of the Amoco Chemicals.
Hydex® is a registered trademark of the A. L. Hyde Co.
We believe this information is the best currently available on the subject. It is subject to revision as additional knowledge and experience is gained. The A. L. Hyde Company makes no guarantee of results and assumes no obligation of liability whatsoever in connection with this information. Anyone intending to use recommendations contained in this publication should first satisfy himself that the recommendations are suitable for his use and meet all appropriate safety and health standards. This publication is not a license to operate under, or intended to suggest infringement of any existing patents. References to products not of A. L. Hyde manufacture do not indicate endorsement of named products or unsuitability of other similar products.
Copyright © 1999 A. L. HYDE Company
Last Modified: November 2, 1999