Preparation and Characterization of High Melt Strength Polypropylene
Using isotactic polypropylene(iPP)as the powder,benzoyl peroxide(BPO)as the initiator,trimethylolpropane triacrylate(TMPTA)as the graft monomer,styrene(St)as the co-monomer,the high melt strength polypropylene(HMSPP)without gels was prepared by a twin-screw extruder.The results of Fourier transform infrared spectroscopy(FTIR)and gel permeation chromatography(GPC)indicate that the monomers have been successfully grafted onto the polypropylene molecular chains.Differential scanning calorimetry(DSC)results show that the crystallization temperature of HMSPP increases by 11.8℃.The rheological test results show that the HMSPP exhibits significant shear thinning phenomenon with a longer relaxation time and a lower loss factor,proving the presence of long branched structures.Compared with iPP,the melt strength of HMSPP increases from 0.03 N to 0.37 N,while its impact strength,tensile strength and flexural modulus increase by89.1%,17.5%and42.6%,respectively.
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