Preparation And Characterization Of A Natural Rubber Core/PBMA Or Rubber Core/PST Shell By Grafting Polymerization

As vinyl monomer,butyl methacrylate and styrene are used to graft onto natural rubber,and the different effects of two kinds of monomer were studied when reaction with natural rubber.The grafting of the butyl methacrylate(BMA)/styrene(ST)monomer onto natural rubber using potassium persulfate(KPS)as an initiator was carried out by seeded emulsion polymerization.The effects of NR/BMA or NR/ST mass ratio,initiator amount and reaction temperature on grafting degree and grafting efficiency are investigated using orthogonal experimental design.The NR-g-BMA and NR-g-ST were characterized by Fourier transform infrared(FT-IR)spectroscopy,differential scanning calorimetry(DSC),and transmission electron microscope(TEM).AS for butyl methacrylate,the results show that the grafting degree and grafting efficiency are highest when NR/BMA mass ratio was 100/80,initiator amount was 0.25phr and reaction temperature was 60℃.Meaningwhile,for styrene,the results show that the grafting degree and grafting efficiency were highest when NR/ST mass ratio was 100/80,initiator amount was 0.75phr and reaction temperature was 90 ℃.IR spectra indicated that BMA and ST were successfully grafted onto NR,DSC curves revealed NR/PBMA and NR/ST both were partially compatible system and TEM studies demonstrated NR-g-BMA and NR-g-ST latex particles had a clear NR core/PBMA shell structure and a clear NR core/PST shell structure.But there was a slightly difference on the process of butyl methacrylate and styrene.Relatived to the styrene,butylmethacrylate firstly graft onto natural rubber particles,after inside extroversion reaction,graft copolymerization was carried out with butylmethacrylate themselves and at last,the complete shell structure formed.As for styrene,the complete shell structure firstly formed,then the extroversion introversion graft copolymerization was carried out with natural rubber particles.The blended vulcanized films were prepared according to diffierent mass ratio of graft copolymer(GNR)and natural rubber(NR).Furthermore,the mechanical properties such as tensile strength and tear strength when before and after aging,thermostability,hardness,crosslink density were investigated.The results showed that compared to natural rubber,the tensile strength and tear strength before and after aging of GNR/NR blended vulcanized films significantly increase.Using scanning electron microscope to observe the tensile fracture morphology of blending vulcanization film,found that with NR-g-BMA mass ratio of graft copolymer increased,the surface tended to be more tight and smooth.While,increased NR-g-ST mass ratio,the surface had little obvious change,but the copolumer particles which evenly dispersed in rubber tended to be more and dense.