How Does UV Light Affect Rubber and Plastic? (1/23/2023)

Learn about how different types of rubber and plastic responds to UV light exposure.

Article - January 23, 2023 By LarsonElectronics.com

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How Does UV Light Affect Rubber and Plastic?

Ultraviolet (UV) light imposes degrading effects on different types of materials and surfaces. This process is known as UV degradation, which originally and naturally stems from the sun. However, with the rise of artificial UV lights that emit UV-A, UV-B or UV-C bands (depending on the lamp), UV degradation now extends to indoor locations. Specifically, buildings that use UV lights for sanitation, paint curing, quality inspection, materials testing and machining are prone to this form of damage.

As the deteriorating effect varies from material to material, choosing products made from UV-stable polymers or reinforced with UV-resistant coatings is an effective way to deter UV degradation in work facilities and on machines.

Rubber

Rubber is a resilient manufacturing material that is prone to UV damage in extreme conditions, which can cause the component to lose its elastic features, display cracking or become soft. A 2007 study presented the effects of 300 nm to 700 nm UV light on samples of rubber. All samples represent the same type of rubber found in bridge bearings that connect overhead roadways. Accelerated UV exposure tests were conducted on samples of natural rubber (NR), chloroprene rubber (CR), ethylene-propylene-diene rubber (EPDM) and high damping rubber (HDR) at staggered durations.

The results showed all samples displayed cracking on the surface after 720 hours; though the amount of damage varied depending on the specific type of rubber sample. Scientists concluded in the study that UV light makes rubber stiff and decreases its “elongation at break and tensile strength.” This UV degradation mechanism causes rubber to become hard and brittle.

Plastic

UV degradation of plastic is common and is frequently found on a wide range of outdoor equipment exposed to the sun for long periods of time. This form of UV degradation appears chalky (a fine powder residue) and can fade colors, making coatings look dull. During the degradation process, the photons that make up plastic generate free radicals when exposed to UV light. Catalyst residues and impurities, which may act as receptors, causes the material to become unstable resulting in damage. Cross linking, or hardening of the surface, may also occur and is associated with brittle.

Not all plastics have the same tolerance to UV light. Unmodified plastics, such as polyoxymethylene (POM) and acrylonitrile butadiene styrene (ABS), are more prone to UV degradation compared to polyethylene terephthalate (PET), polyamide 12 (PA12) and polyphenylene oxide (PPO). High-grade plastics that offer resistance to UV light and are less prone to UV damage include polytetrafluoroethylene (PTFE), fluorinated ethylene-propylene (FEP) and polyimide. Damage from UV light on high-strength plastics is usually limited to the surface, roughly 0.5 mm in depth.