Dynamic analysis of the melting behavior of polymers showing polymorphism observed by simultaneous DSC/X-ray diffraction measurements

The melting behavior of isotactic poly(propylene) (iPP) and poly(vinylidene fluoride) (PVDF), which contained several crystal modifications, was measured by simultaneous differential scanning calorimeter (DSC)/wide angle X-ray diffraction (WAXD) measurements. The DSC heating curve of iPP showed at least two endothermic peaks and one exothermic peak. These peaks were assigned to melting of beta- and alpha-modifications of iPP and melt-recrystallization of beta-modification which occurred immediately after starting the melting of beta-modification. The DSC heating curve of a polymer blend of PVDF/poly(methylmethacrylate) (PMMA) (PVDF content was 80 wt%) showed three endothermic peaks, which were assigned to melting of I(beta), II(alpha) and III(gamma)-modifications of PVDF, respectively. The prepared PVDF/PMMA blend film originally contained these three modifications.