You can’t escape the sun, and neither can rubber. You may not realize it because it happens gradually, but the sun’s rays can cause long-term damage to rubber, leading to cracking. That’s why it’s important to understand how the sun causes this damage, where cracking most often occurs, and which types of rubber offer the best resistance.
Cause and Prevention
Ultraviolet (UV) radiation from the sun is a primary cause of cracking. This is due to a process called photodegradation, which breaks down chemical bonds (in this case, polymer chains, molecules bonded together) within rubber. The results include stiffness, loss of elasticity and tensile strength, and surface cracking. Degradation can also be enhanced by ozone, which is generated by UV light. Ozone further affects the chemical compounds in rubber, contributing to cracking.
To ensure UV resistance, some rubbers can be manufactured with additives like stabilizers. Examples include titanium dioxide, zinc oxide, and carbon black, which absorb and scatter UV radiation to prevent cracking or other sunlight-based damage. UV antioxidants, such as p-Phenylenediamines (PPDs), offer a similar result by absorbing radiation to protect the rubber.
Where to Find Cracking
It’s important to know where cracking most often occurs. Rubber in items or tools used outside or in direct sunlight is most prone to damage. Your car’s wiper blades are an example of this, with their frequent exposure to the sun causing them to crack and become less effective. Vehicle tires can also suffer UV damage and develop cracks.
Gardening equipment like hoses and outdoor furniture should be monitored for signs of cracking. Rubber used in construction, such as roofing and window seals, also faces damage from sunlight. Caution should also be applied to indoor locations that use artificial UV lights, such as lamps in medical and storage facilities. Even though these types of light aren’t “real” in the sense that they don’t come from the sun, they can still cause cracking and reduce rubber effectiveness.
Excellent Resistance
Ethylene propylene diene monomer (EPDM) is known for its excellent durability to UV rays and ozone, which is why it’s used in outdoor applications like roofing, electrical insulators, and connectors for wires and cables. Fluorocarbon (FKM, also known as Viton®) is another great choice because of its UV resistance, often found in solar panels and smartwatch bands. Silicone rubber has many versatile characteristics, including high resistance to ozone and UV light. These qualities make it a popular choice for electrical insulation and construction.
If you’re considering using a rubber like EPDM, FKM, or silicone, ensure you understand the demands and application for which you’ll be using it. Consider the type of flexibility, strength, temperature range, and other types of resistance (such as water) you’ll need from the rubber for your specific application. Also, think about how strong the sunlight will be and how much of it will be hitting the rubber.
Shining a Light On Us
If you’re looking for o-rings and seals that are resistant to UV light and ozone, among others, check out our varied list of products. And if you’re looking for help on any rubber project under the sun, reach out to us, and we’ll be glad to help.