The effect of gas desorption on foaming ratio of microcellular foamed plastics

Microcellular plastics (MCPs) are one of the most significant developments in the plastics industry over the last decade. Microcellular plastics keep mechanical strength loss and plastic weight to a minimum through microcells inside MCPs. The size and number of cells inside MCPs have a direct correlation with foaming ratio. The cell size has to be consistent to ensure higher quality of MCPs, and a great number of cells are needed for a high foaming ratio. This underscores the need to control the size and number of cells to meet products' required performance. In the microcellular batch process, saturation and foaming conditions are major factors that influence the size and number of cells. This article describes how desorption time, defined as the time lapse between saturation and foaming processes, affects cell formation. Our particular concern is the effect of varying desorption time on foaming ratio and cell morphology. The general rule is that the shorter the desorption time, the higher the foaming ratio (i.e., more cells of smaller sizes are formed because of more dissolved gas molecules remaining in the sample). In our study, however, an opposite trend was observed for desorption time less than 2 minutes. As such, different desorption times ranging from 1 to 5 minutes were used to systematically investigate the corresponding changes in foaming ratio and cell morphology. A possible mechanism of action for this anomalous phenomenon is suggested.