Influence of heat‐setting temperature on the properties of a stretched polypropylene microporous membrane

Abstract The influence of heat‐setting temperature on the stress–strain curves, differential scanning calorimetry ( DSC ) curves and properties of a stretched polypropylene microporous membrane was studied. It was found that with an increase of heat‐setting temperature, a plastic plateau region in the stress–strain curves and a melting endotherm plateau in the DSC curves became apparent. The permeability and porosity firstly increased with the temperature to 145 °C and then decreased. The pore structure arrangement showed similar changing trend. On the one hand, higher heat‐setting temperature could decrease the shrinkage of the microporous membrane. On the other hand, the crystallization of some chains around separated lamellae during heat‐setting was unfavorable to the properties of the microporous membrane. The occurrence of crystallization during heat‐setting explained the origin of the plastic plateau. For the fabrication of microporous membranes based on the melt‐stretching mechanism with good dimensional stability, heat‐setting is necessary, but too high a heat‐setting temperature can destroy the permeability. © 2013 Society of Chemical Industry