Study Of Polypropylene Grafting Modification And Montmorillonite Filling Modification

As one of the five general plastics,the development of polypropylene(PP)is very rapid in recent years,but general PP has defects such as poor toughness,low temperature brittle and small polar etc,which greatly limit the application scope of PP.At present,functional modification in material preparation and properties of PP receive much concern and have great research value.In this paper,by means of solid phase grafting and aqueous suspension grafting methods,PP graft modification was achieved successfully,and montmorillonite(MMT)filled PP nanocomposites with excellent performance were prepared.Firstly,the diffusion speed of small molecular substances diffuse from the PP surface diffusion to the interior was studied.The experimental results showed that the small molecular substances’ diffusion speed is related with temperature,time,concentration and particle size of PP.At the same time when interface agent diffuse into internal PP,it has a swelling effect on PP,which can improve the diffusion speed of the monomer and initiator agent.Ultrasonic treatment can significantly accelerate the diffusion speed of small molecules,and the order of the small molecules,diffusion speed from fast to slow is:V cyclohexane>VSt>VMAH>VAIBN.Secondly,by using solid phase graft and water suspension graft,PP grafting MAH and St copolymer(PP-g-MAH/St)was prepared.Preparation,storage and graft characteristics of the oxidated polypropylene(OPP)were studied.Copolymerization reaction mechanism was analyzed,and the characterization of the grafted product was carried out.The experimental results showed that temperature,time,initiator concentration,surfactant content,monomer concentration and ratio all have a certain impact on the grafting reaction.Whether it was in the solid phase graft copolymerization system or in the water suspension grafting system,St can significantly improve the MAH grafting ratio and grafting efficiency.With the increase of grafting rate,the molecular weight of the grafting products increases,melt strength increases,hydrophilicity improves further more,thermal stability increases.There is a gradient distribution from the outside to the inside of the graft,and the graft copolymer has an effect of induce β forming nucleation.Peroxide content in OPP is related with initiator concentration,temperature and air velocity etc.Inert atmosphere and low temperature is favorable for OPP storage.Monomer’s grafting rate and grafting efficiency can reach as high as 3.55%,73.65%,but the graft product has certain degradation,thus its thermal stability would decrease.At last,organic modification of the MMT was carried out,and by using melt intercalation method PP/MMT and PP/MMT/POE composite materials were prepared.MMT organic modification and intercalation mechanisms were analyzed,composite material characterization of FTIR,MFR,TG,DTA,XRD,SEM and other testing methods were used.The experimental results showed that,the organic modification formed an ordered high-level spacing montmorillonite structure.For the PP/MMT composite system,a certain amount of OMMT and appropriate PP-g-MAH/St grafting rate can improve the compatibility of montmorillonite and the polypropylene matrix,the mechanical properties,heat resistance and thermal stability properties of materials.The tensile strength of the composite can reach 34.75 MPa,impact strength reach 8.45 kJ·cm-1 50%hot weight loss temperatures increase near 70 ℃ higher than the raw material PP.For PP/MMT/POE composite system,when the content of POE is 15%,the impact strength of the composite reaches 13.70 kJ·cm-1,which is 176%higher than the raw PP,thermal stability is also improved,the spacing of MMT is increased from 1.94 nm to 3.71 nm and 8.88 nm.PP-g-MAH/St has better mechanics and thermal stability than the composite materials prepared by commercially available PP-g-MAH compatible agents.