HDPE's tightly packed, largely linear molecular structure with minimal branching gives it the highest density and stiffness of the polyethylene grades. That stiffness translates into excellent tensile strength and a distinctive crinkly, paper-like feel that is instantly recognizable in retail merchandise bags and grocery sacks.
The same crystalline structure that gives HDPE its strength makes it more brittle than LLDPE or LDPE, with lower elongation and a tendency toward stress whitening and easier tear propagation once a tear initiates. It also has a hazier appearance than the other polyethylene grades, which rules it out for applications where product visibility matters. HDPE is rarely run alone in demanding film applications; it is more commonly blended or layered to add stiffness and strength without inheriting its full brittleness.