The effect of uni-axial orientation on macroporous membrane structure

The effect of uni-axial stretching on the material properties of macroporous poly(vinylidene fluoride) (PVDF) membranes was experimentally determined. Atomic force microscopy (AFM), differential scanning calorimetry, scanning electron microscopy, and digital image analysis were used to characterize physical structure of the membrane before and after stretching. The effects of strain rate, temperature, and total strain on pore aspect ratio, pore area, surface roughness, glass transition temperature, porosity, and membrane thickness were all examined in this study. Membrane stretching was found to dramatically change the pore structure of PVDF membranes, but was found to have little effect on polymeric properties such as glass transition temperature. Current popular AFM characterization techniques were unable to capture the physical changes in the surface morphology.