What are the differences in thermal shock resistance between PVC and polyethylene?

Thermal shock resistance is a critical property for materials exposed to rapid temperature changes. PVC (Polyvinyl Chloride) and polyethylene are two widely used plastics, but they exhibit distinct behaviors under thermal stress.

PVC has a higher glass transition temperature (Tg) of around 80°C, making it more rigid but less flexible at lower temperatures. When subjected to rapid cooling or heating, PVC is prone to cracking due to its brittleness. In contrast, polyethylene, especially high-density polyethylene (HDPE), has a lower Tg (-120°C to -100°C) and remains flexible across a broader temperature range. This flexibility allows polyethylene to better withstand thermal shocks without cracking.

Additionally, polyethylene's semi-crystalline structure provides better resistance to thermal cycling, while PVC's amorphous nature makes it more vulnerable to stress under temperature fluctuations. For applications involving extreme temperature variations, polyethylene is generally the superior choice due to its enhanced durability and resilience.

In summary, while PVC offers higher rigidity and heat resistance, polyethylene outperforms in thermal shock resistance, making it ideal for environments with frequent temperature changes.