Effect of Molecular Structure on Environmental Stress Crack Resistance of Polyethylene Used in Caps and Closures

Environmental stress crack resistance (ESCR) of polyethylene is mainly due to the nature of tie-molecules. Polyethylene crystalline morphology, molecular weight and MWD affect tie-molecules density and movement. Decreasing of lamellas thickness led to more tie-molecules and higher ESCR. As the molecular weight increases the number of tie-molecules increase. It was found that in broad molecular weight distributions, long molecular chains portion crystallized in several lamellas which led to higher ESCR.

Keywords:

Polyethylene , ESCR , tie-molecule , crystallinity , molecular weight distribution