Study On Crystallization, Structure And Morphology Of The Copoly (Vinylidene Fluoride-chlorotrifluoroethylene)

The crystallization and melting behavior, crystal structure and morphologies of the copoly(vinylidene fluoride-chlorotrifluoroethylene) were thoroughly studied with the aim of a better understanding of the crystallization process of this copolymer. The main conclusions read as follows.The crystallization of polyvinylidene(PVDF), polychlorotrifluorethylene(PCTFE) and random copolymers with an approximate 1:1 and 1:3 mole ratio of vinylidene fluoride (VDF) to chlorotrifluoroethylene (CTFE) were analyzed by differential scanning calorimetry (DSC) and polarized optical microscope (POM). The PVDF was found to melt at 160℃, to have a crystallinity of about 33% and to form spherulites when the samples crystallized at 140℃ from the melt. While the melting point and the crystallinity of the PCTFE was 206℃ and about 28%, respectively, and the rod-like crystals were appeared when the samples crystallized at 180℃ from the melt. For the random copolymer with an approximate 1:3 mole ratio of VDF to CTFE, a low crystallinity of 2.6% was observed with a melting point of 80-100℃, whereas the random copolymer with an approximate 1:1 mole ratio of VDF to CTFE did not crystallize at all.The crystallization of a random copolymer with an approximate 1:4 mole ratio of VDF and CTFE was also analyzed by DSC. Amorphous copolymer with such mole ratio of monomers was isothermally crystallized at a temperature in the range of 40 -80℃ and a low crystallization rate and crystallinity were observed. With the increase in crystallization time or temperature, it was found that the melting point shifts to higher temperature and the lamellar thickness increases. The copolymer had a melting point of 118℃ after annealing at 80℃ for 1440h, with a lamellar thickness of about...