Improvement of Cell Opening by Maintaining a High Temperature Difference in the Surface and Core of a Foam Extrudate
- 1 November 2007
- journal article
- research article
- Published by SAGE Publications in Journal of Cellular Plastics
- Vol. 43 (6), 431-444
- https://doi.org/10.1177/0021955x07079150
Abstract
This article presents an extrusion-based, open-cell foaming process using thermoplastic polymers such as polystyrene (PS) and polycarbonate (PC) with supercritical CO2. Our previous studies have indicated that a cell opening can be promoted by inducing: (i) a nonhomogeneous melt structure by cross-linking, polymer blending, or filler compounding, (ii) cell-wall thinning by a high volume expansion ratio while maintaining soft cell walls, (iii) cell-wall thinning by a high cell-population density, and (iv) plasticization of the soft region of the cell walls with a secondary blowing agent. Until now, the foam extrudate temperature across the cross-section was maintained uniformly for the simplicity of the experiments. In this study, the significant temperature difference between the core and surface of the foam extrudate was induced by surface cooling method. This method increased the chance of cell opening by: (i) increasing the core temperature of the foam extrudate and thereby softening the cell walls, and (ii) decreasing the foam surface temperature to prevent gas loss and thereby increasing the internal gas pressure within the cells. The effects of CO2 content, surface quenching, die geometry, and temperature on foam morphologies were investigated. Low-density, microcellular, open-cell foams were successfully produced. The large intercellular pores were observed from micrographs for both PS and PC foams at optimum processing conditions.Keywords
This publication has 7 references indexed in Scilit:
- Extrusion of microcellular open-cell LDPE-based sheet foamsJournal of Applied Polymer Science, 2006
- Extruded Open-Cell Foams Using Two Semicrystalline Polymers with Different Crystallization TemperaturesIndustrial & Engineering Chemistry Research, 2005
- Increase of open-cell content by plasticizing soft regions with secondary blowing agentPolymer Engineering & Science, 2005
- A diffusion model for water vapor transmission through microporous polyethylene/CaCo3 filmsColloids and Surfaces A: Physicochemical and Engineering Aspects, 2001
- Melt Extruded Open-Cell Microcellular Foams for Membrane Separation: Processing and Cell Morphology RelationshipJournal of Cellular Plastics, 2000
- Polycarbonate hollow fiber membranes by melt extrusionJournal of Membrane Science, 1999
- Preparation of hydrophilic polyethylene foam of open cell type by radiation grafting of acrylic acidJournal of Applied Polymer Science, 1989