Poly(vinylidene fluoride)/submicron graphite platelet composite: A smart, lightweight flexible material with significantly enhanced beta polymorphism, dielectric and microwave shielding properties

摘要

We report a facile technique to fabricate flexible and self-standing films of exfoliated graphite submicron platelets (GPS) impregnated poly(vinylidene fluoride) (PVDF) composite. Detailed structural and thermal characterizations of the fabricated material indicate the gradual increase of electroactive beta-phase in the PVDF matrix with increasing GPs loading and 96% beta phase of PVDF is obtained at 0.5 wt% filler loading. Significant enhancement of remnant polarization value also supports the formation of enhanced electroactive phase. The results obtained for EMI shielding efficiency (in X-band) indicate that PVDF/GPs composites exhibits fair EMI shielding and radar absorption at high filler concentration, whereas dielectric measurement at lower filler concentration (<= 0.5 wt%) shows that electrical property of the composites is dominated by charge storing mechanism resulting high dielectric constant. 400 gm thin composites film can efficiently block 97.5% of incident EM radiation at 8.2 GHz, while a near five times higher dielectric constant is achieved for the composites film having thickness of 300 pm with a low tangent loss. Series-Parallel model was successfully used to describe the filler concentration dependence of the dielectric constant. Therefore the range of composite below and above the critical filler loading (0.5 wt%) can be potentially exploited in thinner, lighter, flexible energy storage, energy harvesting and EMI shielding materials.