The hard elastic high density polyethylene(HDPE)cast film was cold-stretched uniaxially with different stretching ratios and rates in a process of preparing HDPE microporous membranes. AFM

FE-SEM and WAXD were used to observe the variations in the lamellar structure during the cold-stretching processes

and the microporous structure of resulting microporous membranes was evaluated with measurements of porosity and permeability. It was found that increasing cold-stretching ratio could promote the separation of row-nucleated lamellar structure in the films

and be beneficial to the increase of porosity and permeability in the microporous membranes. However

over high cold-stretching ratio led to the collapse of the lamellae

destroying the microporous structure. With the increase of stretching rates

the lamellae was separated to a greater extent

resulting in generation of more micropores and more uniform distribution. During the cold-stretching

the broken micro-second crystals at the lamellae edge and the crystallized long tie chains between lamellae converted to bridges connecting separated lamellae.