Study On Preparation And Properties Of Low Heat Build-up Composite By Latex Co-precipitation Method

In the rubber industry, the solid rubbers and the powder fillers were used as raw material,and the traditional mechanical mixing method was used to prepare masterbatch stock alongwith the rubber processing industry. The traditional mechanical mixing method has theshortcomings of high pollution, high energy consumption, poor working environment.Reinforcing agents, such as carbon black and halloysite nanotubes, could be caused the blackpollution. The carbon black used to reinforcing rubber were nano powders with high surfaceenergy, so it is difficult to disperse the carbon black particles to rubber matrix withmechanical shearing. The nano-particles often aggregated with several microns in the rubbermatrix, causing to damaging the physical and mechanical properties of vulcanizates and highheat build-up. The latex co-precipitation method is a novel technology for preparingmasterbatch using the rubber latex and filler slurry as raw material. The filler particles weredispersed uniformly among the rubber latex particles by liquid mixing. After coagulationco-precipitation, the rubber/filler composites were obtained.In this paper, The NRL/CB composite materials and NRL/CB/HNTs composites wereprepared based on natural rubber latex by latex co-precipitation method. Firstly, the carbonblack dispersion were prepared by using the surfactants, then the stability of dispersion weremeasured by a ultraviolet-visible spectrophotometer. Secondly, the physical and mechanicalproperties of vulcanizates were tested through micro-controlled electronic tensile testingmachine, the dynamic mechanical properties of vulcanizates were tested by RPA2000rubberprocess analyzer and DMA, the heat build-up and heat conductivity were tested throughrubber compression heating machine and rubber thermal analyzer respectively, and finally thefiller dispersed in the rubber matrix by scanning electron microscope. (1)The tensile strength, tear strength,300%modulus and hardness of vulcanizatesprepared by latex co-precipitation method compared to the mechanical mixing method wereincreased by6.5%,4.6%,4.7%and8.8%, while elongation at break decreased by7.3%.Among the vulcanizates prepared by latex co-precipitation method, with increasing of carbonblack particle size, the tensile strength the tear strength and300%modulus first increases andthen decreases. The maximum value occurs when using CB N375. With increasing of thecarbon black structure, tensile strength and tear strength of vulcanizates did not changesignificantly, but100%modulus,300%modulus and hardness gradually increased.(2) The heat build-up of vulcanizates reinforced using the same kind of black by latexco-precipitation method got less and lower temperature. Among the vulcanizates prepared bylatex co-precipitation method, with increasing of carbon black particle size, The heat build-upof vulcanizates decreased. the heat build-up of vulcanized rubber had a minimum whenreinforced by CB N765. With the improvement of the structure of carbon black, the loss factorof vulcanizates decreases, the temperature rise is also reduced compression fatigue.Meanwhile the thermal conductivity of vulcanizates gradually increased, the thermalconductivity of vulcanizate reinforced by CB N375were largest, reaching0.2762W/(m·k).(3)The NRL/HNTs/CB composites with excellent mechanical properties and HNTsuniform dispersion can be prepared by latex co-precipitation method. The mechanicalproperties of the composites in HNTs/CB=20/40were best. With increasing the amount ofHNTs, the degree of cross-linking of composites first increases then decreases, so that tan δ ofthe transition region also first increases then decreases while the compression fatiguetemperature of composites appears a minimum. When using20parts of HNTs substituted CBto reinforce rubber, the compression fatigue temperature of composite dropped10.7℃.Meanwhile improved thermal conductivity, up to0.31W/(m·k).