Preparation and properties of graphene functionalized polyvinylidene fluoride dielectric composites

In order to obtain the composites with high dielectric properties, polyvinylidene fluoride (PVDF) was used as matrix, graphene oxide modified by ionic liquid as filler (GO-IL) and GO-IL/PVDF binary dielectric composites with different GO-IL contents were first prepared by solution blending method. And then, hydroxylated barium titanate (BT-OH)-GO-IL/PVDF ternary composites with different proportions were prepared by solution blending. The effects of GO-IL and BT-OH contents on the thermal, mechanical and electrical properties of the composites were investigated by FTIR, FESEM, XRD, tensile, electrical and differential scanning calorimetry (DSC) tests. FTIR test shows that IL is successfully grafted on GO, and the addition of GO-IL promotes β-crystal formation of PVDF. DSC and XRD characterizations further improve that the addition of GO-IL promotes the growth of β-crystal. The crystallinity reaches 35.3% and 36.9% when the filler is 2% GO and 2% GO-IL, respectively. Electrical test shows that GO-IL is easier to form local conductive networks in PVDF matrix, promoting the electronic displacement polarization and improving the dielectric constant of the composites. For GO-IL/PVDF composite, when the content of GO-IL filler is 2%, the dielectric constant of composites reaches 24.28, which is 2.6 times of pure PVDF. However, when the filler content reaches 8%, the dielectric constant of the composite reaches 78.46, and the dielectric loss also increases sharply, reaching 2.25. The resistance of the composite is 1-2 orders lower than that of pure PVDF. When the content of GO-IL is 2% and the content of BT-OH filler is 20%, the composite shows the best comprehensive properties, the dielectric constant is 40.32 and the dielectric loss is 0.38.