Cooperative effect of shear and nanoclay on the formation of polar phase in poly(vinylidene fluoride) and the resultant properties

The polar crystalline phase is the most important crystal mode for poly(vinylidene fluoride) (PVDF); its high content is urgently desired in the large-scale processing fabrication likes injection-molding. In this study, we proposed a convenient pathway to achieve large amount of polar phase in injection-molding part through cooperation of exerting oscillatory shear field and adding nanoclay. The effects of these two factors on the polymorphic composition were well demonstrated by infrared spectroscopy and X-ray diffraction. The increment of polar phase content was limited when shear field was solely imposed or only less amount of nanoclay, 1 wt%, was added. Whereas, by simultaneously exerting shear field and adding 1 wt% nanoclay, an extremely high polar phase fraction was achieved. So a positive cooperative effect of shear and nanoclay on the formation of polar phase can be proved absolutely. The simultaneously exerting shear and adding nanoclay leaded to not only high content of polar phase but also highly oriented structure. With this unique structure, an order-of-magnitude increase in the ductility (elongation) as well as good piezoelectric property has been achieved for the molded parts of PVDF/nanoclay nanocomposites.