Effect of solution-blended poly(styrene-co-acrylonitrile) copolymer on crystallization of poly(vinylidene fluoride)

Effect of solution-blended poly(styrene-co-acrylonitrile) (SAN) copolymer on crystallization of poly(vinylidene fluoride) (PVDF) was investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). Acrylonitrile segment in SAN copolymer was partially miscible with PVDF. Styrene segment in SAN reduced the copolymer's polarity and its miscibility with PVDF. FTIR and WAXD tests both showed as-prepared PVDF was mainly β-phase. We employed an index Aβ divided by Xc, suggesting that blended SAN could decrease the content of β-phase of PVDF. By DSC, the smaller content of PVDF made the system more misci- ble so that the Tg,SAN of pure SAN decreased from 86.6 to 81.6°C of sample PVDF/SAN = 20/80; further increase PVDF to 50/50, the Tg,SAN had a relative increase to be 84.2°C. However, for SAN by melt molding, Tg,SAN increased with the increase of PVDF content, which might be due to the incorporation of SAN into inter-spacing of PVDF lamellae, because PVDF molecular chains had not enough mobility to retreat from the SAN's embrace and crystallize despite of the exit of SAN.