Preparation Of BR/SBR/NR Foam And Study On Its Structure And Properties

Rubber foams have been used commercially in a wide range of applications including impact,gaskets,sound deadening,thermal insulations,and shoe products due to its cellular.The aim of the industry was prepared the material which was the lighter and higher property.In this paper,Ternary composites of 1,4-cis polybutadiene rubbers(BR),styrene-butadiene rubber(SBR),and natural rubber(NR)foams containing chemical blowing agents Oxybis(benzene sulfonyl)hydrazide(OBSH)were prepared by one-stage and two-stage compression molding technique.The effect of temperature,precure degree,feeding volume on the structure and properties of BR/SBR/NR foams were investigated,and the kinds of chemical blowing agent and the two compression molding technique of BR/SBR/NR foams were compared to the shrinkage.The foaming and vulcanizate characterics of BR/SBR/NR foams were synchronous tested by foam force rheometer(FFR).This study was also focus on the relation between structure and properties by magnetism resonance crosslinking density spectrometer(XLDS),scanning electron microscopy(SEM),differential scanning calorimeter(DSC),The results were obtained as follows:The FFR results shown,with the increasing of temperature,the pressure was increased gradually,and the maximum foaming rate and the maximum cure rate was increased and shift to earlier.The two rates at 150?were the closest than those of other temperatures,only 44 seconds.The time of the maximum foaming rate was ealier only 13 seconds than that of the maximum cure rate at precured degree of 30%.The precured degree also had great influence on the crosslink structure.Equilibrium swelling technique and XLDS measurement were both shown consistency results that crosslink density was increased with the increasing of precured degrees.DSC showed that each curve exhibits two steps in heat capacity for BR/SBR/NR blend.With the increasing of precured degrees,the two groups of Tgs was shift to the higher temperature.With further increasing the precured degrees,SEM and mechanical property showed that the average cell size declined,cell wall thickness became thicker and cell distribution became narrower,and tensile strength,tensile modulus,elongation at break and tear strength were all increased.The crossover point of density,hardness and impact resilience were and persented at precure degree of 30%.The results of the effect of various feeding volume on the FFR were presented that the range of feeding volume between 70%-80%synchronous appeared the typical vulcanization process and foam process clearly.With the increasing of feeding volume between 60%and 90%,the cell size decreases obviously,the cell wall thickness becomes thinner apparently,and the number of cells per cubic centimeter increases obviously.The effect of the kinds of chemical blowing agent and compression molding technique on the properties were investigated.The blowing agent H had great influence on vulcanization and foaming characteristics.The blowing agent H cooperated with OBSH was the best way to prepare the foams in this system.With the increasing of time,density and shrinkage were increased.The shrinkage could be effective reduced by two-stage compression molding technique.All in all,BR/SBR/NR foams were prepared by two-stage compression molding,and the first precured technique was120?×T30,the second technique was 150? ×(T90-T30),and the feeding volume was 90%,which could prepared BR/SBR/NR foams with the uniform cell.