Fabrication of Fine-celled PP/Ground Tire Rubber Powder Composites Using Supercritical Carbon Dioxide

PP/Ground Rubber Tire (GRT) powder microcellular blend foams were prepared by supercritical carbon dioxide. The effects of blend composition like the content of GRT and maleic anhydride-grafted polypropylene (PP-g-MA) on crystallinity, solubility, diffusivity, morphology and mechanical properties of PP/GRT microcellular composites were studied. The results showed that the PP/GRT composite foams with a unique bimodal (large and small) cellular structure, in which the large-cells embrace a GRT powder. Depending on the composition, generally, the higher content of GRT results in the smaller cell sizes, higher cell densities and relative densities, whereas the 20 wt% GRT composite shows the lowest relative density. The mechanical properties of the microcellular PP/GRT composite foams are directly related to the blend composition and the processing conditions. The PP-g-MA/GRT (50/50) produced microcellular foams with a very fine and uniform cell structure, lower relative densities and improved mechanical properties.