Inert Gases as Alternative Blowing Agents for Extruded Low-Density Polystyrene Foam

Abstract

A 1.25" segmented single screw extruder was custom designed and used for foaming polystyrene with physical blowing agent such as carbon dioxide, nitrogen, and argon. The type of gas, the pressure, nucleating agents, and the extrusion conditions were found to be of significant importance affecting density cell size, cell size distribution, and foam stability. The lowest density achieved was3 lbs/cu.ft. Melt pressure oscillation was found to be a problem, which could be addressed by the addition of talc or endothermic nucleating agents.

Foamability of Cellulose Palmitate Using Various Physical Blowing Agents in the Extrusion Process

“…Blowing agents can be divided into physical and chemical blowing agents depending on the gas production method. Physical blowing agents are, for example, low boiling point organic hydrocarbons (e.g., isobutane and pentane) [ 6 , 7 , 8 ] or inorganic materials (e.g., nitrogen, carbon dioxide, water, and argon) [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ] that are added to the polymer matrix as liquid or gas and usually go through a phase change during foaming. Chemical blowing agents (e.g., sodium bicarbonate, citric acid, and azodicarbonamide) [ 14 , 15 , 16 ] produce gaseous products through chemical reactions, usually decomposition upon heating.…”

Gas atomization of high molecular weight polymers: feasibility studies and process development

“…A large aspect of polymer processing with supercritical fluids revolves around solubility of the fluid in the polymer. Polymer/gas system solubility is often described by Henry's Law [16][17][18], given [19][20][21][22][23][24][25][26][27][28]. Supercritical fluids, as a solvent, not only reduce the viscosity of its polymer solute, but also have a viscosity lower than their own liquid counterpart [14].…”

“…Gas-assisted extrusion technology was chosen because of its ability to decrease the viscosity of molten extruded materials. It is known that gas injection is used in the production of polymeric foams from materials such as polystyrene and polypropylene [ 17,32], which are the selected materials of interest for advancing polymer atomization to higher molecular weight materials. Carbon dioxide was selected specifically as the injecting agent a variety of reasons.…”