Study On Long Chain Branching Reaction Of Polyprppylene

In order to prepare long chain branching polypropylene and improve the melt strength of polypropylene,the reaction rule of polypropylene with different reactive monomer (TAIC,PETA,FS,RES,DVB) and polymer(modified EVA and SBS) was studied by general single screw extruder in this paper.Experiment results showed that 1,4-benzodiol (RES) and Divinylbenzne(DVB) can improve the melt strength of PP obviously,and enhance the application value of PP.In order to investigate the modification effect of RES and DVB,melt reaction rule of polypropylene with RES and DVB was studied.The results showed that the most suitable initiator was Dicumyl peroxide(DCP),when RES was 0.2wt%,the melt strength of modified PP can increase to 8KPa.s that was 4 times than raw material,when DVB was 0.4wt%,the melt strength of modified PP can increase to 30KPa.s that was 15 times more than that of the raw material.In modified process,co-monomer styrene can restrain degradation and crosslink of PP,and increase the long chain bracning structure in PP.PP melt properties were modified with DVB by various extruders,including single screw extruder,twin-screw extruder and grafting reactive extruder,it was found that the most suitable extruder was single screw extruder.The modified PP prepared by single screw extruder was tested and characterized, Experiment results showed MFR of modified PP decreased obviously,melt strength was 15 times more than that of the raw PP and higher than the Basell Corporation HMS-PP,the melt properties of PP were improved evidently.When DVB was 0.6wt%,the gel of modified PP was 0.4 wt%but had no influence on the process ability of material.The extruding diameter of modified PP increased to 4.3mm that was 2 times more than raw PP,it was suggested that the long chain branching structure existed in modified PP.The capillary rheometer test showed apparent shear viscosity and viscous activity energy of modified PP increased obviously,the apparent shear viscosity of modified PP increased from 1340Pa.s to 8975Pa.s.The FTIR showed that the molecular structure was not changed during reactive extrusion. The DSC and WAXD showed that T_m and T_c increased obviously,β-crystalline had formed in modified PP.The mechanical property test showed that tensile strength and impact strength of modified PP increased obviously.