Study on the Rheological Properties and Analytical Methods of Polyvinylidene Fluoride Solutions for Lithium Electric Adhesives
The relative molecular mass of polyvinylidene fluoride(PVDF)used for lithium electric adhesives is relatively high.According to the polymerization technique,PVDF could be divided into two categories,emulsion-polymerized PVDF and suspension-polymerized PVDF.Due to the structure differences,the rheological properties of the two PVDFs are unlike.In this paper,the molecular structures and rheological properties of PVDFs produced by the emulsion and suspension methods were systematically studied by using gel permeation chromatograph,differential scanning calorimeter,nuclear magnetic resonance spectrometer and rotary rheometer.The results show that there are some microgels and a few branched structures in emulsion-polymerized PVDF.The suspension-polymerized PVDF has long straight chain structures,a higher melting point,and a higher crystallinity.The rheological properties of the two PVDF solutions are very different.The viscosity of emulsion-polymerized PVDF is relatively high at low shear rate,the critical shear rate of shear thinning is lower.The suspension-polymerized PVDF shows the first Newtonian region at low shear rate and has a high critical shear rate.Besides,through investigating the relationships between the PVDF solution rheological properties and the relative molecular mass,the relationships between the zero shear viscosity of long straight chain PVDF solution and the weight-average molecular weight are obtained.The established relationship makes it feasible to calculate the PVDF weight-average molecular weight by the rheological method.
万方数据
维普
