Polgmeric Foaming and its Process Development

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The effect of processing variables such as concentration of dissolved gas, release rate of pressure and operation temperature on bubble growth dynamics, nucleation rate and final bubble size was examined by both simulation and fundamental experiments. In the polyolefin foaming process, fundamental experiments showed that bubble size increased when the release rate of pressure decreased, whereas bubble size decreased when the operating temperature decreased. Furthermore, a higher concentration of dissolved gas resulted in smaller bubble size. These results were confirmed by numerical simulation that was newly developed in this project. The simulator was developed based on Shafs nucleation and bubble growth models. Both simulation and experimental results elucidated that release rate of pressure, concentration of dissolved gas and operating temperature are the principal factors which control bubble size and foaming density in the polymeric foaming process. Optimal design of die remained as one of the unsolved problems.