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The microcellular foaming process consists of the saturation process for dissolving gas molecules into plastic and the subsequent foaming process for cell formation. Foaming characteristics of microcellular plastics (MCPs) such as foaming ratio and cell morphology are largely determined by the saturation conditions, particularly by the saturation pressure. In this study, we investigate the effects of saturation pressure on the foaming characteristics of MCPs, when the quantity of dissolved gas (or the weight gain) is kept constant. Because the weight gain of a specimen is an increasing function of saturation pressure, different desorption times are used in order to maintain the same weight gain across specimens from different saturation pressures. Contrary to the common belief, for specimens with the same weight gain higher saturation pressures lead to lower foaming ratios. A hypothesis for the underlying mechanism and a practical ramification of the phenomenon are discussed. [ABSTRACT FROM AUTHOR]

Microcellular plastics (MCPs) are manufactured through a batch process comprised of saturation and foaming stages. In the saturation process, gas molecules are dissolved into plastic in a high-pressure vessel. Following the saturation process, micro-cells are formed inside the plastic as the gas-dissolved plastic sample undergoes the foaming process. In this paper, we investigate the effects of repeating the batch process on the formation of MCPs. Because the plastic sample after the first batch process has developed microcells, these pre-existing cells are expected to affect the second round of the batch process. Of particular interest is the effect of repeated saturation at different saturation pressures. Experiments show that repeating the batch process can lead to favorable outcomes in terms of foaming ratio and cell morphology, which are otherwise unattainable particularly with a single batch process. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]