Study On The Microstructure Adjusting And Toughening Of Polypropylene Composites

The fabrication of toughened polypropylene(PP)materials with balance between strength and toughness is an important task in toughening modification of thermoplastic resin.It is of great scientific significance for the development of toughening modification theory of polymers,and it also has significant engineering value for the fabrication of PP materials with high performance.Therefore,in this work,we tried to establish the "structure-property" relationship of PP blends and PP composites and to achieve the balance between strength and toughness of PP materials.The main achievements are as follows:(?).Different kinds of polyethylene were used to study the influence factors of toughening efficiency for polypropylene/ethylene propylene rubber/polyethylene(PP/EPR/PE)blends with polymeric core-shell particles.The corresponding toughening mechanism was also established.A pretty good interfacial strength between the core and shell is critical to transmit the stress between phases.The intrinsic meaning of the "equivalent rubber content" can be concluded:the shear yielding of the core promoted by the pressure stress that the shell puts on the core plays the same role as the cavitation of rubber shell.Then the interparticle distance decreases,and the percolation of stress volumes happens.(?).A combination of styrene-[ethylene-(ethylene-propylene)]-styrene block copolymer(SEEPS)and EPR was used to toughen PP,and the balance between strength and toughness was achieved.Dynamic mechanical properties and phase morphology observations demonstrate that EPR component and EP domain of SEEPS are completely miscible,and they form the compound rubber phase.The incorporation of SEEPS also increases the "equivalent rubber content",and consequently PP/EPR/SEEPS blends present excellent low-temperature toughness.(?).The PP composites with excellent low-temperature toughness were prepared by introducing hydrophobically modified SiO2 nanoparticles into PP/EPR blends,and it can also tailor the brittle ductile transition temperature(Tbd).The results of impact strength demonstrate that compared with PP/EPR blends,PP/EPR/SiO2 composites own much lower Tbd,and their Tbd decreases with the increase of EPR content and SiO2 content.Inspiringly,a Tbd as low as-45 ? was obtained.Phase morphology results show that the silica nanoparticles are located at the interface of PP and EPR,and the interfacial area increases due to the decreased size and more irregular shape of rubber particles.The rubber particle size,interparticle distance and interfacial area were studied systematically,and a quantitative correlation between Tbd and interfacial area was established.