How does the crystallinity of polyethylene influence its resistance to stress cracking?

The crystallinity of polyethylene plays a critical role in determining its resistance to stress cracking. Higher crystallinity levels result in a more tightly packed molecular structure, which enhances the material's mechanical strength and rigidity. However, this increased crystallinity can also reduce the polymer's flexibility, making it more susceptible to stress cracking under prolonged strain or environmental exposure.

Semi-crystalline polyethylene, with a balance of amorphous and crystalline regions, often exhibits better stress cracking resistance. The amorphous regions provide elasticity, allowing the material to absorb stress, while the crystalline regions contribute to overall toughness. Factors like molecular weight, branching, and processing conditions further influence crystallinity and, consequently, stress cracking behavior.

Understanding this relationship helps in selecting the right polyethylene grade for applications requiring long-term durability, such as piping, packaging, and automotive components.