Authors: Jing Cao Na Wen Yuying Zheng
Publish Date: 2016/07/28
Volume: 34, Issue: 9, Pages: 1158-1171
Abstract
Long chain branched polypropylene random copolymers LCBPPRs were prepared via reactive extrusion with the addition of dicumyl peroxide DCP and various amounts of 16hexanediol diacrylate HDDA into PPR Fourier transform infrared spectrometer FTIR was applied to confirm the existence of branching and investigate the grafting degree for the modified PPRs Melt flow index MFI and oscillatory shear rheological properties including complex viscosity storage modulus loss tangent and the ColeCole plots were studied to differentiate the LCBPPRs from linear PPR Differential scanning calorimetry DSC and polarized light microscopy PLM were used to study the melting and crystallization behavior and the spherulite morphology respectively Qualitative and quantitative analyses of rheological curves demonstrated the existence of LCB The effect of the LCB on crystalline morphology crystallization behavior and molecular mobility and thereby the mechanical properties were studied and analyzed Due to the entanglements between molecular chains and the nucleating effect of LCB LCBPPRs showed higher crystallization temperature and crystallinity higher crystallization rate more uniformly dispersed and much smaller crystallite compared with virgin PPR thus giving rise to significantly improve impact strength Moreover the LCBPPRs exhibited the improved yield strength The mobility of the molecular chain segments as demonstrated by dynamic mechanical analysis DMA was improved for the modified PPRs which also contributed to the improvement of their mechanical properties
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