Preparation And Application Of Hydroxylethyl Methacrylate Grafted Natural Rubber Latex

By grafting vinyl monomer onto natural rubber （NR） molecules, the properties of naturalrubber can be significantly improved and the applications of natural rubber can be greatlyextended. In this paper, The grafting copolymer with semi-interpenetrating polymer networksfrom2-hydroxyethyl methacrylate （HEMA） and natural rubber （NR） latex was synthesized byemulsion method using cumene hydroperoxide/tetraethylene pentamine as initiator systemand triethylene glycol dimethacrylate （TEGDMA） as crosslinking agent. The changes ofgrafting ratios and grafting efficiencies with the swelling conditions, the reaction time andtemperature, the concentrations of crosslinking agent, initiator and monomer wereinvestigated. The molecular structure and rubber particle morphologies of grafting productswere characterized by FT-IR, Particle Sizer and TEM, respectively and the hydrophilicity wasdetermined using telescopic goniometer. Furthermore, the anti-coagulation behaviour againstblood for NR-g-HEMA films, the bonding effect of NR-g-HEMA-basaed adhesives andNR-g-HEMA latex used as interfacial compatilizer of composite materials were alsoevaluated.The swelling temperature and times of monomers against NR latex particles were found tobe of great effects on the grafting copolymerization and the appropriate swelling conditionswere16°C×20h. The optimal conditions for preparing NR-g-HEMA latex were preferred bysingle-factor experiment method. The mass ratios of m（monomer）:m（NRL）:m（initiator（CHPO:TEPA=1:1））:m（crosslinking） were20:100:0.2:0.1and the reaction conditions were8h×16℃. And a grafting ratio of NR-g-HEMA up to14%can be obtained at these conditions. FT-IR analyses of NR-g-HEMA and TEM observation of latex particles implied that thepoly（HEMA） molecular chains were attached firmly onto the NR latex particles. After graftedwith poly（HEMA）, the water contact angle of NR-g-HEMA latex film decreased graduallywith the increase of grafting ratio due to the hydrophilicity of poly（HEMA） and could bereduced to about71oas the grafting ratio was up to14%. TGA results showed that the thermalstability of modified NR-g-HEMA was higher than that of NR.The blood compatibility of NR-g-HEMA films was evaluated by platelet adhesionmeasurement. It showed that the number of adhered platelets on the NR-g-HEMA latex filmdecreased greatly with the grafting ratio up to14%, and the platelets were disk shaped. Thecorresponding NR-g-HEMA adhesives with different grafting ratios were prepared. Then theplywood was pressed by the adhesives, and the bonding properties of plywood were measured.The shear strength test showed that the polarity and adhesive properties of the adhesivesincreased with the increasing grafting ratios of NR-g-HEMA latex. And the maximum shearstrength（1.88Mpa） of corresponding plywood increased by84%compared with NR latexadhesive. In addition, the effect of NR-g-HEMA latex used as interfacial compatilizer ofNR/SiO₂composite materials was also evaluated. The results showed that the tensile strengthand tear strength of composite materials increased by22%and36%respectively, by adding3phr of14%NR-g-HEMA latex when the content of SiO₂was8phr. It showed that theaddition of NR-g-HEMA latex could improve the dispersion of SiO₂in natural rubber latex bySEM observation, but the amount of NR-g-HEMA latex couldn’t more than half of the SiO₂amount. Thermal analysis results showed that the thermal stability of NR/SiO₂compositematerials could be improved by adding in NR-g-HEMA latex.