Contribution of residual solvent to the nucleation and reinforcement of poly (vinylidene fluoride)

Poly (vinylidene fluoride) (PVDF) films or membranes are generally produced using solution media, and this process raises two interesting questions which deserve to be explored, i.e., whether residual solvent exists and what is the effect of any residual solvent on the structure and properties of the PVDF matrix. Samples with residual N-N-dimethylformamide (DMF) were prepared via a solution precipitation method followed by different drying times. Fourier transform infrared spectroscopy results demonstrated that residual solvent existed in the PVDF matrix even although the samples were dried for 72 h at 60 °C. This can also be verified by energy dispersive X-ray spectroscopy results. Results of differential scanning calorimetry revealed that the residual solvent promotes the nucleation of PVDF markedly during its crystallization. Both dynamic mechanical and melt rheology tests showed that elastic moduli are greatly increased owing to the reinforcement in samples containing DMF residual.