Modification Of Natural Rubber Latex By Graft Copolymerization Of 2-Ethylhexyl Acrylate And Methacrylic Acid

Natural rubber(NR)grafted with 2-ethylhexyl acrylate(2-EHA)and methacrylic acid(MAA,collectively NR-g-PEHA/MAA)was synthesized by emulsion polymerization.To further enhance its mechanical properties by adding trimethylolpropane tris(3-aziridinylpropanoate)as crosslinking agent before the latex film formation and curing at room temperature.In this paper,the effects of reaction temperature,feeding mode,monomer and initiator concentration on mechanical properties,thermal properties,swelling degree,viscosity,monomer conversion and particle size were investigated.The grafted products were characterized by FT-IR,TEM),TGA,DSC,universal electromechanical machine and nanometer particle size and Zeta potentiometer.The results showed that the mechanical properties,thermal stability and solvent resistance of NR-g-PEHA/MAA were improved compared with natural rubber(NR).The successfully graft of 2-EHA and MAA onto the NR skeleton were confirmed FT-IR.The morphology of NR latex and NR-g-PEHA/MAA particles were observed by TEM.It was found that the grafted polymer chains were wrapped on the surface of NR particles,and the particles with small size were more easily grafted.It was found that optimal mechanical properties were obtained under the following conditions:reaction temperature at 50°C,2-EHA at 14.7 phr,initiator concentration at 0.8 phm,and functional monomer MAA at 0.3 phr,with MAA being fed at 7 h after initiation of the redox reaction.The optimal tensile strength,elongation at break,toughness,and elastic modulus were 8.45 MPa,1279%,37.64 MJ/m~3,and 1.69 MPa,respectively.The thermal stability of the modified product has also been improved.The decomposition temperature of the best-performing NR-g-PEHA/MAA at a mass loss of 5%and 50%was 16?and 12?higher than that of NR,respectively.The change of the glass transition temperature(T_g)before and after NR modification was too little to be observed.The crosslinking degree of NR-g-PEHA/MAA was characterized by toluene swelling finding that the swelling degree fluctuated around 10 g/g.The system viscosity of the modified latex was tested,and the result showed that the viscosity of the sample with the best mechanical properties was 13.67 c P,and the change of viscosity of NR-g-PEHA/MAA latex mainly depended on the MAA content and feeding mode.And the process and formulation of emulsion production affected the monomer conversion and emulsion particle size by controlling the reaction activity,the length of graft chain,the number of crosslinking points and the content of oligomers in the aqueous phase.