BUBBLE REMOVAL IN ROTATIONAL MOLDING

摘要

Simple closed form solutions have been obtained for bubble dissolution in typical polymer melts encountered in rotational molding. The solutions are in excellent agreement with experimental data available in the literature. Using these closed form solutions it is shown that under typical rotational molding conditions the polymer melts may be almost saturated. As a result, bubble shrinkage occurs over long periods. Depending on the degree of saturation, surface tension may contribute substantially to the concentration gradient that drives bubble shrinkage. A pressure increase imposed on such an almost saturated polymer melt leads to a steep concentration gradient in the vicinity of the bubble/melt interface that can lead to extremely fast bubble shrinkage. The effect of surface tension on the rate of bubble shrinkage is negligible under such undersaturated conditions.