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 temperatu re and pressure. From visual inspection the aged material appeared not to be homogeneous. Therefore, samples from three distinguishable regi ons were compared with a sample cut from the virgin material by studyi ng their small-and wide-angle X-ray scattering (SAXS and WAXS). The re sults show that plasticizer has vanished from the aged material, the c rystalline layer thickness distribution has narrowed, amorphous lamell ae are collapsed and voids have been created. Within the aged material the number of voids varies: there are more at the inner surface and f ewer 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 propo sed, which only requires a simple kind of SAXS measurement.