Poly (vinylidene fluoride)/multi-walled carbon nanotube composites: Polymorphs transformation induced ductility

Poly (vinylidene fluoride)/multi-walled carbon nanotube (PVDF/MWCNTs) composites with different filler loadings were fabricated via a combined method of solution mixing and melt blending. Excellent CNT dispersion was seen by electron microscopy. With very low CNT content, prepared composites display significantly enhanced ductility as compared with neat PVDF which results in largely increased fracture toughness with the context of no loss in modulus. With as low as 0.2 wt. % CNT loading, the elongation at break has been almost quadrupled. Investigations show that the elevated ductility (toughness) originates from the polymorphs transformation of PVDF matrix. A minor γ phase PVDF was obtained in composite samples and this phase gradually disappeared with the development of stretching. It is believed that this γphase continue to feed and transformed into β crystalline during the stretching. The disassembly of γphase and re-assembly into β phase create a plasticized section around CNT. This plasticizing zone-like section leads to striking increase of ductility of the composites.