초록
The crystal structure of the blends of poly(vinylidene fluoride) (PVDF) and poly(vinyl acetate)(PVAc), ethylene/vinyl acetate (20/80) copolymer (PEVAc80), and ethylene/vinyl acetate (30/70) copolymer (PEVAc70) has been studied using a polarizing microscope equipped with a heating stage and an FT -IR spectrometer. The spherulitic morphology in the PVDF/PEVAc blend appeared as three different types, i.e., lamellar splay, concentric, and spiral type. As crystallization temperature and the content of amorphous PVAc and PEVAc80 miscible with PVDF increase, concentric ring and spiral ring type spherulites are formed more easily than in the case of PVDF and a PVDF/PEVAc70 blend system. The extinction band periodicity between the bright zone and the dark zone in the ring-banded spherulites observed under a crossed polarization was found to increase with increasing content of PVAc and PEVAc. Furthermore, the periodic distance between neighboring spiral arms increased from the core to the outer edge, and this may be ascribed to the preferential rejection of PEVAc chains into the inter-spiral regions during crystallization. The FT-IR analysis of samples quenched from the melt to various temperatures shows increase in $\beta-phase$ content as the amounts of PVAc and PEVAc80 blended increase and as the quenching temperature is reduced. In conclusion, the crystal morphology and structure in the PVDFIPVAc and PVDF/PEVAc blend systems were shown to be highly associated with the degree of miscibility of an added amorphous polymer with PVDF.
