Relationship between UV transmittance and poly(vinylidene fluoride) crystal structures of poly(vinylidene fluoride)/poly(methyl methacrylate) blends after annealing

In this study, we will report the relationship between crystal structures of poly(vinylidene fluoride) (PVDF) and UV transmittance of poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blends heat-treated in several ways. Crystallinity of the annealed samples (QA), heat treated Q samples increased in all blend ratios. We examined the dependence of UV transmittance on the weight fraction of PVDF. UV transmittance of QA samples, except for 80 wt% PVDF, decreased from that of Q samples. S samples and the annealed samples (SA), heat-treated S samples, showed low UV transmittance. The wide angle X-ray diffraction (WAXD) curves of PVDF 80 wt% blends are very different. It seems that QA sample has the crystal structure of PVDF (I). On the other hand, SA and S samples have PVDF (II) structure. Q sample is amorphous. It is known that different crystalline structures are obtained according to the crystallization speed. It is considered that the crystallization speed of PVDF 80 wt% QA sample is comparatively slow and form me PVDF (I) structure. The difference of refractive indexes between PVDP (I) and PMMA is smaller than that between PVDF (II) and PMMA. Therefore, PVDF 80 wt% QA sample, in spire of its high crystallinity, has high UV transmittance.