How does the length of polymer chains affect their tensile strength in materials such as plastics?

Longer polymer chains give materials more points to pull apart, so they can stretch further before breaking, which often means higher tensile strength. As chains grow, the bonds between them become more numerous and the chains can slide and reorganize under stress, distributing the force over a larger area. This sliding reduces the chance that a single weak spot will cause a fracture, so the material resists tearing better. For example, a polyethylene film with very long chains can stretch twice as far as one made with short chains before it snaps. Thus, chain length usually improves a plastic’s ability to hold up under pulling forces.