Preparation And Properties Of High Melt Strength Polypropylene

High melt strength polypropylene is a polypropylene resin which has a high meltstrength and perfect melt elasticity. It was expanded in foam, thermoforming and extrusioncoating areas. The researches on it has a great significance. In this paper, The high meltstrength polypropylene was prepared successfully by the means that long chain monomer that1,6-hexanediol diacrylate(HDDA) was grafted on PP. In order to improve the performance ofthe polymer of PP, the β nucleating agent was added to the materials.First, the grafting modification of the difunctional monomer DVB and HDDA on PPwere studied respectively. The graft copolymer PP-g-DVB and PP-g-HDDA was prepared bythe twin-screw extruder, with dicumyl peroxide(DCP) as initiator.Grafted products wasdetermined by formula method of melt flow rate (MFR) and melt strength (MS). The effectsof DVB and HDDA concentration, sag resistance and thermal stability on PP gel content wereinvestigated. The grafted Products were characterized by Fourier Transform infraredspectroscopy (FTIR), thermogravimetric analysis (TGA) and so on. The results showed thatthe grafted products PP-g-DVB and PP-g-HDDA all have high melt strength, goodresistance to sag resistance, and high heat resistance temperature characteristic; while theDVB monomer concentration was1%,the gel content of the grafted products PP-g-DVB is10%, and with the increasing of concentrations of monomer, gel content increased gradually.In the products of PP-g-HDDA, the gel content all less than1.5%, and which is far less thanPP-g-DVB products; The grafted products FTIR spectra showed monomer DVB and HDDAwere grafted onto the backbone of PP.Secondly，the reaction grafting dual monomer St-HDDA on polypropylene to preparethe high melt strength polypropylene products was studied. The effects of speed screwrotation, initiator concentration, reaction temperature on the grafting reaction wereinvestigated, and the effects of the monomer styrene(St) and HDDA mole ratio on the PP gelrate and melt strength were also researched. The results showed that when the mole ratiobetween the St and HDDA is1:1, the less product gel content, the more high melt strength;the best screw rotation speed is180r/min; the best reaction temperature is190℃; The bestconcentration of initiator is0.04%; The grafted products FTIR spectra showed that doublemonomer St-HDDAhave been all grafted onto the backbone of PP.Finally, the high melt strength and high tenacity PP products was successfully preparedby the β nucleating agent introduced into the reaction system. The effects of the PP raw material, the mechanical properties of the products on the concentration of β nucleating agentwas investigated, And characterizations were carried out such as XRD,TGA and mechanicalproperties and so on. Analysis results indicated that after adding β nucleating agent, the βspherulites content improved greatly, And the PP maintained the characteristics of highrigidity and impact strength raised remarkably, this is the reason why the product has goodimpact properties; the β nucleating agent was introduced in the PP-g-(St-HDDA) product,which making the products having improved Performance.