Study On Microstructure And Properties Of PP/Liquid Nitrogen Ground Tire Rubber Powder Composites

Polypropylene(PP)/liquid nitrogen ground tire rubber powder(LGTR)were melt blended by a twin-screw extruder in this subject.The toughening modification,reinforcing modification and preparation of PP/LGTR composites were studied.The first part is the toughening modification of PP/LGTR composites.Mechanical properties and microstructure of the compounds were investigated.The result indicated that mechanical properties of the PP reduced with addition of LGTR.But notched impact strength increased with the LGTR content.Compatibility of two phase got better with addition of compatibilizer resulted in the improving of mechanical properties.Notched impact strength and compatibility improved with addition of polyolefin thermoplastic elastomer(POE)or maleic anhydride grafted with EPDM(EPDM-g-MAH).Using high density polyethylene(HDPE)/POE as a toughing system could further improve the toughness and notched impact strength of the blends.The second part is the reinforcement modification of PP/LGTR composites.The effects of different fillers material and high temperature treatmenton mechanical properties of blends were studied,The dispersion and content of filler in substrate were studied too.The result indicated that the masterbatch and calcined kaolin can improve the mechanical properties of the blend system better than the other two filler materias,Considering the performance and cost,15 parts of mica or calcined kaolin are the best.The mechanical properties of the blend system were further improved by high temperature treatment.Mica and calcined kaolin are dispersed well in the substrate and all kinds of fillers are lost in the processing process.The third part is the research on the preparation process of PP/LGTRcomposites.Mechanical properties and microstructure of the compounds were investigated.The result indicated that the Mechanical properties of of the blends was best when the screw speed was 145r/min with the injection pressure was 90 bar and the holding time was 36 S.The mechanical properties of the blends could be improved with the smelting of LGTR and the best process was 60℃ smelting 5min.Mechanical properties and compatibility of the PP/LGTR blends could further be improved with high temperature treatment.The fourth part is the research on processing flow performance and surface quality of PP/LGTR composites.The influence of different brands of PP on the processing fluidity of PP/LGTR composites was studied by comparing the melting index differences of PP/LGTR composites obtained by mixing different brands of PP and LGTR,the effect of lubricant on the processing fluidity of PP/LGTR composites was studied.The effects of processing technology and brightener on the surface quality of products were studied.The result indicated that the processing fluidity of PP/LGTR composites is mainly affected by PP.The higher the PP melting index,the better the processing fluidity of PP/LGTR composites and the use of lubricant can improve the processing fluidity of PP/LGTR composites.When the screw speed of extruder is 120 rpm,the injection pressure is 70 bar and the holding pressure is 75 bar,the surface quality of products is better,and the use of brightener can effectively improve the surface quality of products.