Effect of composition ratios and mixing steps on properties of BR/NR/NBR blends and blends foam

Abstract

This research is aimed to prepare foam from BR/NR/NBR blends which should integrate key property of these three rubbers. BR possesses high abrasion resistance but low tensile strength while NR possesses high tensile strength [1]. The addition of NBR was advantage for non-polar solvent resistance [2]. The effect of the mixing steps of rubber with vulcanizing additives on vulcanization of rubber and on mechanical properties and foaming of BR/NR/NBR were reported. The ratios of BR/NR/NBR were various as 60/20/20, 40/40/20 and 20/60/20. The vulcanizing additives used for rubber compounding were 5 phr ZnO, 2 phr stearic acid, 1.5 phr MBTS and 2 phr sulfur. The first part of the work was to study the effect of mixing step on rubber blends. Compounding system I was carried out by masticated BR, NR and NBR on a two-roll mill after that vulcanizing agent was added consecutively obtaining BR/NR/NBR rubber compounds with various rubber compositions. Rubber compounds were then characterized and vulcanized in order to investigate vulcanizate properties. In System II, three rubbers were mixed separately with required vulcanizing additives on the two-roll mill, obtaining BR, NR and NBR compound containing the same content of vulcanizing agent. Then the compounds were blended to obtain compound blended for the same blend ratios in System I. The blended rubber compounds were then characterized and vulcanized for their properties. In term of rubber blend foaming these two mixing systems were also used to compound the rubbers by addition foaming agent into the compound during mastication or blending of rubber on the two-roll mill. The results showed that mixing step affected the properties of rubber compound and vulcanizate in rubber blend. As various rubbers were mixed in different step resulting in different viscosity and hence affect foaming of rubber and subsequently properties of rubber foam.