Abstract
High-pressure high-temperature sintering (HPHTS) is a novel recycling technique that makes it possible to recycle vulcanized rubber powders made from waste rubber (namely scrap tires) through only the application of heat and pressure. A brief look into the mechanism of sintering will be presented along with information about the influence of molding variables, such as time, temperature, pressure and rubber particle size on the mechanical properties of the produced parts. One of the most interesting observations is that powders of every crosslinked elastomer attempted sintered together via this technique, including silicone rubber (SI), sulfur cured [natural rubber (NR), ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR)], peroxide cured butadiene rubber (BR), and fluoroelastomers (FKM). Early work on sintered rubber made from commercially available rubber powder had a modulus of 1 to 2 MPa, strength of 4 to 7 MPa and an elongation at break of 150–250%. Recently, in-house ground samples of SBR have had sintered values over 9.5 MPa strength and 275% elongation, or greater than 60% retention of the original properties. Many of these mechanical properties are comparable with industrially manufactured rubbers, and it is believed that recycled rubbers produced via HPHTS offer the potential to replace virgin rubber in numerous applications.
