An open-celled structure was produced using polystyrene and supercritical carbon dioxide in a novel batch process. The required processing conditions to achieve open-celled structures were predicted by a theoretical model and confirmed by the experimental data. The theoretical model predicts that at least a saturation pressure of 130 bar and a foaming time between 9 and 58 s are required for this system to produce an open-celled structure. The foaming temperature range has been selected to be higher than the polymer glass transition temperature yet not higher than a temperature limit where the gas starts leaving the system. The experimental results in the batch foaming process verified the model substantially. The SEM pictures showed the presence of pores between the cells, and the mercury porosimetry test results verified the overall open-celled structure. Experimental results also showed that by increasing the saturation pressure and the foaming temperature, there was a drop in the time required for open-celled structure formation. At saturation pressure of 130 bar, foaming temperature of 150 °C and a foaming time of 60 s, open-celled microcellular polystyrene foams were obtained using supercritical CO2 in the batch process. Based on the results, a schematic diagram, depicting the process of foam structure formation from nucleation to bubble coalescence and gas escape from polymer, was proposed. Theoretical calculations showed that by increasing foaming time, cell size was increased and cell density was reduced and the experimental results verified this prediction.
Microcellular foam Open-celled structure Open-celled model Processing parameters Bubble coalescence
This is a preview of subscription content, log in to check access.
The authors wish to thank Tarbiat Modares University due to financial and logistics supports.
Krause B, Boerrigter ME, van der Vegt NFA, Strathmann H, Wessling M (2001) Novel open-celled polysulfone morphologies produced with trace concentrations of solvents as pore opener. J Membr Sci 187:181–192CrossRefGoogle Scholar
Krause B, Münüklü P, van der Vegt NFA, Wessling M, Sijbesma HP (2001) Bicontinuous nanoporous polymers by carbon dioxide foaming. Macromolecules 34:8792–8801CrossRefGoogle Scholar
Park CB, Padareva V, Lee PC, Naguib HE (2005) Extruded open-celled LDPE- based foams using non-homogeneous melt structure. J Polym Eng 25:239–260CrossRefGoogle Scholar
Lee PC, Wang J, Park CB (2006) Extruded open-celled foams using two semicrystalline polymers with different crystallization temperatures. J Appl Polym Sci 102:3376–3384CrossRefGoogle Scholar
Huang Q, Seibig B, Paul D (2000) Melt extruded open-cell microcellular foams for membrane separation: processing and cell morphology. J Cell Plast 36:112–125CrossRefGoogle Scholar
Janani H, Famili MHN (2010) Investigation of a strategy for well controlled inducement of microcellular and nanocellular morphologies in polymers. Polym Eng Sci 50:1558–1570CrossRefGoogle Scholar
Colton JS, Suh NP (1987) Nucleation of microcellular foam: theory and practice. Polym Eng Sci 27:493–499CrossRefGoogle Scholar
Park HS (2007) Surface tension measurement of polystyrene in supercritical fluids. PhD Thesis, University of WaterlooGoogle Scholar
Matuana LM, Park CB, Balatinecz J (1997) Processing and cell morphology relationships for microcellular foamed PVC/wood-fiber composites. J Polym Eng Sci 37:1137–1147CrossRefGoogle Scholar
Famili MHN, Janani H, Enayati MS (2011) Foaming of a polymer-nanoparticle system: effect of the particle properties. J Appl Polym Sci 119:2847–2856CrossRefGoogle Scholar
Kumar V, Suh N (1990) A processing of making microcellular thermoplastic parts. Polym Eng Sci 30:1323–1329CrossRefGoogle Scholar
Krause B, Mettinkhof R, van der Vegt NFA, Wessling M (2001) Microcellular foaming of amorphous high-Tg polymers using carbon dioxide. Macromolecules 34:874–884CrossRefGoogle Scholar
Park CB, Behravesh AH, Venter RD (1998) Low density microcellular foam processing extrusion using CO2. Polym Eng Sci 38:1812–1823CrossRefGoogle Scholar
Kumar V, Weller J (1994) Production of microcellular polycarbonate using carbon dioxide for bubble nucleation. J Eng Ind 116:413–420CrossRefGoogle Scholar