Effect Of Xanthate Accelerator And Modified Calcium Carbonate Whiskers On The Properties Of NRL Film

Natural rubber latex has excellent comprehensive properties and it is widely used in impregnated products and extruded products.However,in the process of using,the mechanical properties still have to be needed further improved such as tensile strength and tear strength.This project investigates the natural rubber latex film from two directions of accelerator and filler,aiming to improve its comprehensive mechanical properties.In terms of accelerators,five different xanthates which are zinc methyl xanthate?ZMX?,zinc ethyl xanthate?ZEX?,zinc n-propyl xanthate?ZPX?,zinc n-butyl xanthate?ZBX?,and sodium n-butyl xanthate?SBX?were synthesized by wet alkali method.And their physical properties were analyzed by Fourier transform infrared spectroscopy tester and simultaneous integrated thermal analyzer.The results show that the characteristic absorption peaks of xanthates appear in all five substances.The order of thermal degradation stability from small to large is ZMX,ZEX,ZPX,ZBX.The degradation temperatures of xanthates are all above100°C,and they can be applied to low temperature vulcanization of nature rubber latex as accelerators.The effect of zinc xanthates with different lengths of alkyl segment on the properties of natural rubber latex film were studied.The ZMX,ZEX,ZPX and ZBX were added to the natural rubber latex in different amounts to prepare vulcanized films.It is found that the reduction of the length of the alkyl segment lead to a decrease in the performance of nature rubber latex film which are vulcanized by zinc xanthates in the same amount.The more the amount of the same accelerator the higher the crosslink density of the vulcanized film.The mechanical property first increases and then decreases with the increasing of xanthates,and the performance is optimal when the amount is 2 phr.the difference between zinc xanthate and common accelerators called zinc diethyl dithiocarbamate?ZDC?were investigated,ZDC vulcanized films were prepared.The results express that the comprehensive performance of films vulcanized by ZBX and ZPX are better than those by ZDC,but the performance of films vulcanized by ZEX and ZMX vulcanized films are inferior.The difference in vulcanization between zinc salt of xanthate and sodium salt were researched,the film vulcanized by SBX were prepared.The results indicate that the vulcanization effection of the sodium salt is lower than that of zinc salt.The vulcanization formulas were optimized when temperature was 60°C and the time of process was 2 h.The results show that the best vulcanization formula is that the amount of sulfur,the accelerator,zinc oxide is 1 phr,2 phr,1 phr,respectively.In terms of filler,the calcium carbonate whiskers were surface treated by polydopamine?PD?with different modification time.The surface characteristics of the modified calcium carbonate whiskers?PD-CaCO₃?were analyzed by contact angle meter and spectroscopy tester and scanning electron microscope.The consequeces reveal that the loading of PD becomes saturated after 2 h of modification.The contact angle of PD-CaCO₃ whisker is less than 90°.The amount of PD adhesion on PD-1-CaCO₃ whisker is less when modification time is 1 h;PD is distributed uniformly on the surface of the PD-2-CaCO₃ when modification time is 2 h;The load of PD on PD-3-CaCO₃ whisker is more when modification time is 3 h,but there is an aggregation of the PD.PD-CaCO₃ whiskers with different modification time were added to the natural rubber latex to prepare composite films.The mechanical properties,thermal stability,SEM of the tensile and tear sections of the film were analyzed.Experiment results show that the mechanical properties of composite films from high to low in order is PD-2-CaCO₃/NRL composite film,PD-3-CaCO₃/NRL film,PD-1-CaCO₃/NRL film,CaCO₃/NRL film.In order to the effect of the amount of PD-2-CaCO₃ on the properties of the film was researched,different amounts of PD-2-CaCO₃ were added to the natural rubber latex to prepare composite films.With the increase of the amount of PD-2-CaCO₃ whiskers in the natural rubber latex,the thermal stability of the composite films increases gradually,and the mechanical properties increases first and then decrease.When the dosage is 5 phr,the comprehensive performance of the film is best.It can be seen that the PD-CaCO₃ whiskers are tightly bonded to the rubber matrix by scanning electron micrograph to observe the fracture surface of the film,it indicates that PD is effective to modify the surface of calcium carbonate whiskers,and the calcium carbonate whiskers can fully exert the reinforcing effect in the latex.