Thermoplastic elastomers from polypropylene — powdered rubber scrap blends
Polimery 1997, No 7-8, 491
When vulcanized in an internal mixer under specific shearing conditions at temperatures exceeding the melting point of PP and with sulfur or cumylperoxide or (sulfur + cumyl peroxide) used as a crosslinking agent, powdered rubber waste—PP blends gave thermoplastic materials exhibiting properties close to those of thermoplastic elastomers. Studies on the content of polymer-bound sulfur in, and on the solubility of, the resulting materials in selective solvents (chloroform, xylene) at elevated temperatures showed the chemical reactions of dynamic vulcanization to involve bonding of sulfur by the polymer, continued crosslinking reactions and degrading of the powdered scrap, and PP transformations including grafting of PP on powder particles. Compared with the original PP, the resulting materials were characterized by enhanced impact strength at -20°C, greater elongation at break, and still acceptable breaking strength.