Toughening of polypropylene with recycled Tire-rubber

Abstract

The immiscible blends of recycled tire rubber, ither reclaimied tire-rubber or ground rubber tire and homolypropylene had been investigated. TGA demonstrated that reclaimed tire-rubber was the miscible mixture of devulcanized natural rubber, styrene-butadiene rubber and butadiene rubber, wheres ground rubber tire was the mixture of vulcanized natural rubber, styrene-butadiene rubber and butadiene robber. These blends were prepated by melt-mixing in two consecutive machines, firstly a two-roll mill and then a counter-rotating twin screw extruder. Two types of crosslinking agents, sulfur with other additives or maleic anhydride and dicumyl peroxide, were added into the blend during milling. After injection to the impact specimens, they were subjected to the measurement for their notch-lzod impact strength. In addition, the melt flow index, thermal properties and surface mprphology of these blends were also observed. It was found that homopolypropylene/ground rubber tire blends, with three different mesh sizes of ground rubber tire, at the ration of 70/30 had similar impact strength which were slightly higher than homopolypropylene. However, it was observed that homopolypropylene/ground rubber rubber tire blend, containing ground rubber tire with mwsh size of 40, exhibited the highest impact strength for both vulcanization using sulfur crosslinking agent and non-vulcanization. In case of homopolypropylene/reclaimed tire-rubber blends, various ratios, i.e., 80/20, 70/30, and 60/40 were attempted both with vulcanization using sulfur crosslinking agent and without vulcanization. The homopolypropylene/reclaimed tire-rubber blends at 70/30 had highest impact strength for both vulcanized and non-vulcanized blends. When maleic anhydride/dicumyl peroxide was used, it was found that higher impact strength of the hompolypropylene/reclaimed tire-rubber blend at 70/30 was obtained. This could be attributed to the cohesion the polymer chains in each phase, homopolypropylene phase and ruber phase, and the interfacial adhesion between homopolyropylene and reclaimed tire-rubber chains in these two phases. Such phenomena would lead to good dispersion and distribution of reclaimed tire-rubber in homopolypropylene matrix as clearly exhibited in their scanning electron micrograhs.