Study of crystallization behavior of neat poly(vinylidene fluoride) and transcrystallization in carbon fiber/poly(vinylidene fluoride) composite under a temperature gradient
The crystallization behavior of poly(vinylidene fluoride) (PVDF) and transcrystallization in carbon fiber (CF)/PVDF composite were investigated under a temperature gradient. The crystallization temperature (Tc) was controlled in the range of 110 180 degC. For neat PVDF, the results showed that exclusive g phase formed at Tc above 164 degC, but coexisted with a phase at Tc ranging from 137 to 160 degC. The promotion of g phase to nucleation of a phase at low Tc was observed for the first time. For CF/PVDF composite, a cylindrical transcrystalline (TC) layer formed on the surface of CF when Tc was between 137 and 172 degC. The TC layer was exclusively composed of g phase at Tc above 164 degC. The hybrid nucleation was dominated by g phase though some a phase nuclei emerged on the surface of CF when Tc was in the range of 144 160 degC. As Tc decreased, competition between the hybrid nucleation of a and g phase became more intense. The g phase nuclei was soon circumscribed by the rapidly developed a phase when Tc was below 144 degC. Furthermore, some a phase nuclei were induced at the surface of the g phase TC layer, and developed into a phase TC layer when Tc was in the range of 146 156 degC, which resulted in a doubled TC layer of a and g phase at the interface of the composite. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43605.