TPE Pellets Breaking Down Under Heat? Here’s How to Respond

During the processing and use of TPE pellets, prolonged or brief exposure to high temperatures can cause molecular chains to break and oxidize, leading to yellowing, brittleness, a sticky surface, and a significant decline in mechanical properties. This is known as thermal degradation. It not only affects the appearance and feel of the finished product but also shortens its actual service life.

So how can we address thermal degradation in TPE pellets?

The editors at Zhongsu Wang recommend adopting a systematic approach to control thermal degradation by addressing formulation, processing, structural design, and usage conditions.

1. Formulation adjustments form the foundation.

The heat resistance of TPE pellets largely depends on the selection of the base material and additive system. Replacing SBS with SEBS eliminates unsaturated double bonds in the molecular chains, thereby structurally enhancing resistance to thermal and oxidative aging. Regarding antioxidants, combining a hindered phenolic primary antioxidant with a phosphite secondary antioxidant can continuously trap free radicals during thermal processing, thereby slowing the progression of oxidative chain reactions. The choice of plasticizing oil is equally critical; high-purity, multi-hydrogenated white oil is more stable at high temperatures, less prone to oxidation and volatilization, and can reduce the risk of TPE pellets becoming brittle after prolonged exposure to heat. If necessary, a small amount of nano-montmorillonite or carbon black can be added to slow the penetration of oxygen and heat into the material through physical barrier effects.

2. Process controls directly influence the extent of thermal degradation of TPE pellets during processing.

While ensuring proper plasticization and mold filling, appropriately lowering the processing temperature can significantly slow the degradation rate. The residence time of the melt in the high-temperature barrel should also be minimized as much as possible; when the machine is shut down, the barrel should be cooled promptly or emptied to prevent static overheating. Screw speed and back pressure should not be set too high, as excessive shear can cause localized high temperatures and result in invisible thermal damage. Pre-processing drying is equally important; moisture vaporization at high temperatures can induce hydrolysis, accelerating the degradation process of TPE pellets.

3. Product structural design can also play a supporting role.

Wall thickness should be kept as uniform as possible to avoid localized areas of excessive material thickness, which can lead to internal stress concentration and cause cracking when released under high-temperature conditions. Mold venting must be unobstructed; trapped oxygen can exacerbate localized oxidation, creating potential issues in molded parts made from TPE pellets. These structural details often only become apparent gradually during thermal aging tests.

4. End-use specifications also warrant attention.

Products made from TPE pellets should avoid prolonged exposure to temperatures exceeding the material's temperature resistance range under actual operating conditions. In high-temperature environments, direct contact with oils, acidic or alkaline chemicals, or uninsulated metal surfaces should also be minimized. These external media accelerate material aging and shorten the service life of TPE pellet products.

Overall, addressing the thermal degradation of TPE pellets requires a combination of formulation optimization, process control, structural design, and usage guidelines. Formulations should establish a solid foundation for heat resistance; processes should minimize processing damage; designs should reduce stress risks; and usage should avoid conditions that accelerate aging. Only when these elements work together effectively can the stability of TPE pellets in high-temperature environments be better ensured.