Property evaluation of mechanically modified thermoset rigid polyurethane foam waste/NBR blends: Effect of blend ratios

Abstract

Burning of rigid polyurethane (PU) foam waste unlike that of natural rubber based product waste as an energy source is generally not performed as it may release toxic gases to the environment, which may lead to the human health issues. Therefore, these wastes are being accumulated in the environment without a proper disposal method. The main aim of this study was to develop a low-cost modification process for rigid thermoset PU foam waste to produce blends with nitrile rubber (NBR) for special applications. In addition to potentially enhancing the qualities and lifespan of the final goods, combining modified PU waste with NBR can help promote environmental sustainability through waste reduction, resource conservation, and energy efficiency. Thermoset rigid PU foam waste was mechanically modified using two roll mill by varying the number of mill passes from 6 to 18 at an interval of 3 mill passes. After evaluation of the properties of the modified PU waste, optimum mill pass was determined. A series of virgin NBR/mechanically modified rigid PU foam waste composites were prepared by varying the percentage of PU foam waste modified using two roll mill from 0 to 30% at 7.5% intervals according to an oil seal formulation. Cure characteristics, physico-mechanical properties such as tensile properties, tear strength, hardness, resilience, abrasion resistance, ageing performance as well as swelling behaviour, crosslink density and oil absorbance of NBR/mechanically modified PU foam waste vulcanizates in toluene and industrial oils were evaluated and compared with those of control vulcanizate. Results indicated that replacement of 30% virgin NBR with mechanically modified rigid thermoset PU foam waste retained 54%, 70% and 83% of tensile strength, elongation at break and tear strength, respectively. Hardness and resilience increased by less than 3%, whereas abrasion volume loss and compression set increased by 44% and 62%, respectively. Modulus at 100% elongation was dropped by 35%. Replacement of virgin NBR with mechanically modified PU up to 15% does not have any marked influence on physico-mechanical properties. Hence, the 85:15 virgin NBR/Modified PU blend compound could be suitable for oil resistant applications.