Studying the Microstructure of Unaged and Aged PVDF by Small- and Wide-Angle X-ray Scattering

A layer from plasticized poly(vinylidene fluoride) (PVDF) was aged by exposing one of its faces to an aggressive fluid at elevated temperature and pressure. From visual inspection the aged material appeared not to be homogeneous. Therefore, samples from three distinguishable regions were compared with a sample cut from the virgin material by studying their small- and wide-angle X-ray scattering (SAXS and WAXS). The results show that plasticizer has vanished from the aged material, the crystalline layer thickness distribution has narrowed, amorphous lamellae are collapsed and voids have been created. Within the aged material the number of voids varies: there are more at the inner surface and fewer at the outer surface beneath the rods of a supporting metal grid. Based on the results of this study and theoretical considerations, a method for the quantitative description of the ageing process is proposed, which only requires a simple kind of SAXS measurement.