Role of the KBr surfaces in crystallization of poly(vinylidene fluoride) films with a KBr powder as a nucleating agent

• We model the crystallization process of PVDF with KBr particles.
• We propose the tailoring method of the high-temperature form of the gamma phase.
• We comprehensively investigate crystallization on the surfaces of additives by DSC, FTIR and SAXS.

We have investigated the crystallization processes of the PVDF films with KBr particles as a nucleating agent by using mainly the DSC measurements. The crystallization processes of the PVDF film containing KBr particles can be explained on the basis of the morphological observations by Lovinger. KBr additive accelerates the nucleation of the γ-form crystallites rather than that of the α-form ones with the epitaxial effect of the KBr surfaces on the nucleation of the γ-form crystallites. The γ-form crystallites grown precedently play a role as the nucleation sites in the α-form crystallization. In the middle temperature range, the overgrowth of the α-form crystallites pins the growth of the γ-form crystallites. Furthermore, the solid–solid phase transition of the α-form crystallites to the γ-form ones takes place from the interfacial regions between the α-form crystallites and the γ-form ones even in the early stage of crystallization. This results in the production of a film having exclusively the γ-form crystallites for a short crystallization time.

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