Effect of poly(methyl methacrylate) addition on the dielectric and energy storage properties of poly(vinylidene fluoride)

Poly(methyl methacrylate) (PMMA) was introduced into poly(vinylidene fluoride) (PVDF) via a solution blending process, and a series of PVDF/PMMA blends were obtained in an effort to reduce the energy loss of pure PVDF. The effects of the composition and thermal treatment on the properties of the polymer blends were carefully studied. The results show that the introduction of PMMA led to a lower crystallinity and a smaller crystal size of PVDF for its dilution effect. As a result, the dielectric constant and energy storage density of the polymer blends were slightly reduced. Meanwhile, the phase transition of the PVDF crystals from the α phase to the β phase happened during the quenching of the blend melt to ice-water; this was also observed in the untreated or annealed blends with PMMA contents over 50 wt %. Compared with the α-PVDF, the PVDF crystals in the β phase possessed a lower melting temperature, a higher dielectric constant, and a lower dielectric loss. The addition of PMMA reduced the energy loss of PVDF significantly, whereas the energy storage density decreased slightly. The optimized blend film with about 40 wt % PMMA and PVDF in the β phase showed a relative high energy storage density and the lowest energy loss.