Carbon nanotubes accelerated poly(vinylidene fluoride) crystallization from miscible poly(vinylidene fluoride)/poly(methyl methacrylate) blend and the resultant crystalline morphologies

• CNTs promoting PVDF crystallization from miscible PVDF/PMMA blend is demonstrated.
• Two types of spherulites with different degrees of thermal stability are observed.
• Accelerated phase separation during crystallization by adding CNTs is proposed.
• CNTs exhibit double effects of nucleation and inducing phase fluctuation.

A few acidized carbon nanotubes (CNTs) (0.2 and 0.5 wt%) were introduced into miscible poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend with a certain weight ratio of 50/50. The dispersion states of CNTs were comparatively investigated using optical microscope, scanning electron microscope and transmission electron microscope. The crystallization behaviors of PVDF component were systematically investigated through different strategies, including nonisothermal crystallization, isothermal crystallization, and the strategy that combined melt-annealing with nonisothermal crystallization. Polarized optical microscope, differential scanning calorimetry and rheometer were used to investigate the crystallization behaviors. The results showed that CNTs exhibited homogeneous dispersion in the PVDF/PMMA/CNT blend composites. The crystallization of PVDF component from miscible PVDF/PMMA blend was greatly accelerated by adding CNTs. Specifically, it was observed for the first time that the two types of spherulites, i.e. ring-banded spherulites and compact spherulites, which were simultaneously induced during the isothermal crystallization process, exhibited different degrees of thermal stability. The latter spherulites exhibited higher thermal stability compared with the former spherulites. The crystallization of PVDF component could be further enhanced after the samples being melt-annealed at high temperatures. It was suggested that the accelerated crystallization of PVDF component from miscible PVDF/PMMA blend was not simply attributed to the nucleation effect of CNTs but possibly attributed to the joint effects of CNT nucleation and inducing phase fluctuation during the crystallization process.

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