How does the molecular weight of polyethylene influence its impact strength?

The molecular weight of polyethylene (PE) plays a crucial role in determining its impact strength, a key property for applications requiring durability and resistance to cracking. Higher molecular weight polyethylene generally exhibits greater impact strength due to longer polymer chains that enhance entanglement and energy absorption during deformation.

Low-density polyethylene (LDPE) with lower molecular weight tends to be more flexible but less impact-resistant, while high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE) offer superior toughness. The increased chain length in UHMWPE, for example, improves resistance to wear and impact, making it ideal for demanding industrial uses.

Crystallinity and branching also interact with molecular weight—linear PE with high molecular weight has higher crystallinity, further boosting impact resistance. Understanding this relationship helps engineers select the right polyethylene grade for specific performance needs.