Papers by Author: Chul B. Park

Abstract: Microcellular foaming behavior of polypropylene/polystyrene (PP/PS) composites with or without the addition of nanoclay was compared in an extrusion foaming process by using supercritical CO₂ as the foaming agent. The influence of CO₂ content on foaming of the composites was investigated in the study. Our experiment results demonstrated that the introduction of nanoclay dramatically improved the foaming of the PP/PS blends with increased cell-population density and decreased cell size. With the increase of CO₂ injected in the foaming process, cell-population density of the foam samples further increased.

Abstract: In this study, the effects of annealing temperature and annealing time on the crystallinity of polylactide foams were investigated. The foam samples were prepared through a tandem extrusion line by using CO₂ as a blow agent. The research results showed that crystallinity of foamed samples could be significantly increased by annealing. The optimum annealing temperature and annealing time to achieve high crystallinity were varied according to the cell morphology of foams.

Abstract: The effect of PDMS on foamability of R-PP was investigated using a single screw extrusion foaming system, with supercritical carbon dioxide as the blowing agent. Experimental results indicate that the addition of a small amount of PDMS will improve expansion ratio of R-PP foamed samples. Furthermore, compared with pure R-PP, cell-population density of foamed samples obtained from R-PP/PP-g-MAH/PDMS blends was obviously higher than that of pure R-PP foams.The experimental results show that blending with PDMS is beneficial for improving foaming performance of R-PP.

Abstract: Recently, a novel processing route for fabricating microcellular ceramics has been developed. The strategy for making the microcellular ceramics involves: (i) forming some shapes containing a mixture of preceramic polymer, expandable microspheres and optional fillers by a conventional ceramic forming method, (ii) foaming the compact by heating, (iii) cross-linking the foamed body, and (iv) transforming the foamed body into microcellular ceramics by pyrolysis. The flexural strength and compressive strengths of the microcellular ceramics were investigated; values up to 30 MPa and 100 MPa, respectively, were obtained at room temperature. The superior mechanical properties were attributed to homogeneous distribution of cells in microcellular ceramics.