Investigation of effects of different nanoparticles and ionic additives on the microstructure and crystallization behavior of PVDF

In recent years, interest has been increasing in efficient, environmentally friendly, self-operating piezoelectric materials. Polyvinylidene fluoride (PVDF) is a semi-crystalline thermoplastic polymer that attracts attention with its high thermal and mechanical strength, flexibility, biocompatibility and electroactive properties. In particular, the piezoelectric properties of PVDF are directly related to its electroactive polar β phase structure, in which the same atoms are arranged in the same direction on the chain. Nowadays, composites of PVDF that support these properties are being investigated. In this thesis, the effects of different types of nano-sized particles and ionic additives on the crystallization behavior and microstructure of PVDF were examined. Among the additives, aluminum oxide nanowire, zinc oxide and organoclays were used as nano-sized particles, and polydadmac was used as ionic additive. Samples were prepared at 1-5% by weight using the melt blending and solution casting method. Dimethyl formamide (DMF) was used as the solvent and a laboratory type double screw blending device was used for melt blending. It was pressed into a film to remove the thermal history and to prevent any solvent remaining in the composite. Among the composites containing organoclay were found to be sufficient for the kinetic study, and their kinetic properties were examined by crystallization at constant temperature and different cooling rates with thermal analyzes performed on a differential scanning calorimeter (DSC) device. Relative crystallinity values were calculated from the area under the crystallization curve and the compatibility of the calculated kinetic data with Avrami, Ozawa, Liu-Mo and Jeziorny models was evaluated. The effects of additives on the microstructure of PVDF were determined by fourier transform infrared spectroscopy (FT-IR) analysis. When the data were evaluated, it was determined that organoclays had nucleation effect by increasing the initial temperature of crystallization in non-isothermal conditions, made crystallization more difficult in according to kinetic data and significantly increased the formation of the electroactive β phase.