In the expanding industry of polymer processing, a prominent area of current research is to process polymers efficiently without creating any environmental hazards. Processing of poly(2,6-dimethy1-1,4-phenylene oxide) (PPO) requires high processing temperature and toxic plasticizers due to its high glass transition temperature (T-g) and phenylene oxide groups in the backbone. Very few research works have reported the use of superheated liquids to process high T-g, intractable polymers. This research work presents a systematic study to explore the advantages of processing PPO with superheated liquids composed of two nontoxic and ubiquitous polar liquids, ethanol and water. Microcellular foams of PPO having a density range from 0.13 to 0.56 g/cm(3) can be produced with the aid of superheated ethanol, water and ethanol/water mixtures. Such foams also exhibit high specific strength. In addition, PPO can also be extruded with superheated ethanol or ethanol/water mixtures at a temperature, which is 150-180 degrees C below the conventional extrusion temperature for PPO.