Study On Core-shell Structure Toughening PP Composite Materials

As one of the five common plastics, polypropylene (PP) with a rich source of rawmaterials, light weight and high cost performance has gained rapid development, therefore, itsapplication has become even more widely. However, pure PP has poor toughness at lowtemperature and strong tendency to be notched. In order to fill up a deficiency in PPperformance, a great number of studies on toughening modification and quality improvementhave been made at home and abroad and some great breakthroughs has been made inmulti-phase copolymer and blending. Such typical technologies as a rubber toughenedtoughening, thermoplastic elastomer toughening, and other inorganic fillers toughening havebeen applied. Mass fraction of low-modulus component content added in rubber toughenedtoughening and thermoplastic elastomer toughening is higher than15%. Processing of fillinginorganic filler is relatively complicated.This thesis prepared the composite particles with inorganic core-shell by emulsionpolymerization. Since such core-shell composite particles can modify properties of PP, asystematic study on its formulation, microstructure and macroscopic properties have beenmade in order to improve the toughness of PP and perfect the technoloy of toughening,thererfore to apply PP in more fields and promote its development in a functional andhigh-tech way.Specific methods and results are as follows:(1) The composite particles with inorganic-organic core-shell are prepared by emulsionpolymerization and its synthesis according to different addition of initiator, porcelain clay,PMMA monomer are characterized.(2) Initiator/porcelain clay/PMMA monomer blends are melted,casted belts and cuttedinto granules by the single-screw extrude. Rheological behaviour of the blends arecharacterized by rheometers.(3) Dynamic mechanical analysis of blends are analysed by dynamic mechanical analyzerand the effects of tougheners of core-shell are characterized. (4) Surface morphology of the core-shell composite particles and fractured surface of PPblends are observed by scanning electron microscope.(5) Mechanical testing such as tension testing and collision testing of core-shellcomposite particles and PP blends are made and the toughening effect exerted on PP blendsby the core-shell composite particles is demonstrated.The results show that core-shell composite particles act as stress concentrationcenters,inducing a large number of crazes and shear zones, even causing crazing branches. Alot of energy is consumed in producing crazes and shear zones, which results in the delay ofmaterial destruction effectively and improvement of impact strength at room temperature.This will strongly prove that composite particles with core-shell can modify toughness of PPeffectively. In addition, composite particles with core-shell can reduce the viscosity of blendsand increase the...