Effect of heat-treatment temperature after polymer melt and blending ratio on the crystalline structure of PVDF in a PVDF/PMMA blend

We analyzed control of the crystalline structure of poly(vinilydene fluoride) (PVDF) in a PVDF/poly(methylmethacrylate) (PMMA) blend by varying the polymer blend ratio (PVDF/PMMA=60/40, 70/30 and 80/20 wt%) and the heat-treatment temperature (160–210?°C) just after the polymer melt. We obtained PVDF (form I) limitedly by heat treatment at 185 and 190?°C after blending PVDF/PMMA 70/30 wt%. The samples produced under other conditions indicated PVDF (form II). Results of differential scanning calorimetry (DSC), polarized light micrography and light transmittance indicated that samples of PVDF/PMMA 70/30 wt% heat-treated at 185 and 190?°C exhibited high compatibility between PVDF and PMMA, respectively. In contrast, PVDF (form II) samples obtained in other conditions indicated lower compatibility. We assumed that PVDF crystalline structure became the structure of the PVDF (form I) according to decrease of the crystallization rate by the highest compatibility between PVDF and PMMA. Pure PVDF crystallized very fast, so PVDF (form I) cannot be developed from pure PVDF by simply controlling the heat-treatment temperature.