A Study of the Solubility of Blowing Agents in Foam Extrusion Systems

MIHAYASHI Tsuyoshi, MOTANI Shigeru, HAYASHI Takahiro, YOSHIDA Hiroyuki

doi:10.4325/seikeikakou.3.425

The solubility of fluorocarbon blowing agents in foam extrusion of thermoplastic resin was investigated by both experimental and theoretical approaches. The thermoplastic resin used was polystyrene, while CFC-12 and HFC-134 a were the selected fluorocarbon blowing agents.<br>First of all, in our experimental approach, we developed a direct observation system using a fiberscope, and observed the shape and behavior of gas bubble in the extrusion system. In this experiment, we used CFC-12 as the blowing agent. It was noted that (1) the phenomena called gas dispersion in this field is the same as gas solubility in the resin, (2) huge voids generated in the plastic foam was mainly caused by poor solubility of the blowing agent. We considered the effects of pressure, temperature, and residence time in additional experiments.<br>Next, we constructed a quantitative theoretical model by applying the concept of absorption velocity that is defined for gas-liquid equilibrium for this phenomena. In a numerical simulation based on this model, the results showed good agreement with experimental results.<br>Finally experimental production parameters (pressure, temperature and residence time) were caluclated for HFC-134 a and polystyrene.

A Study of the Solubility of Blowing Agents in Foam Extrusion Systems

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