Conversion of Polyolefin Waste
Professor Nien-Hwa Linda Wang has been conducting investigations that seek to curb the negative impacts of polymer wastes by recycling and reusing the polymers. Since waste from electronic applications of polycarbonates is the fastest growing polymer waste stream, Wang and her team decided to focus their attention on this issue. In one study, the researchers developed a roomtemperature sequential extraction process using solvent mixtures that enabled the recovery of polycarbonates and other polymers from electronic waste. Importantly, the method consumes little energy, has a high yield (>95%), and produces high-purity (>99%) polymers with similar molecular weight distributions as the virgin polymers. The recovery cost is only about 30% of the cost for synthesis of virgin polymers. Recovering high-purity polymers with a high yield is difficult for various reasons, one of which is that polymer wastes are often complex mixtures with extremely variable compositions. The various polymers have similar physical properties and broad overlapping molecular weight distributions, which make their separation quite challenging. Since no single solvent was found to selectively dissolve polycarbonates in the waste, the team created new sequential extraction processes using multiple solvent mixtures. One major benefit is the reduction of environmental hazards associated with the polymer wastes found in landfills or oceans, by introducing financial incentives for collecting and recycling the wastes. Ultimately, Wang’s aim is to develop various mixed-solvent extraction processes that would facilitate effective polymer recycling, thereby reducing the need for raw materials from petroleum and other sources, and significantly reducing CO2 emissions.