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首页> 外文期刊>Chemical Engineering Science >Experimental and numerical studies on the effects of pressure release rate on number density of bubbles and bubble growth in a polymeric foaming process
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Experimental and numerical studies on the effects of pressure release rate on number density of bubbles and bubble growth in a polymeric foaming process

机译：聚合物发泡过程中压力释放速率对气泡数密度和气泡生长影响的实验和数值研究

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A simulation of simultaneous bubble nucleation and growth was performed for a batch physical foaming process of polypropylene (PP)/CO2 system under finite pressure release rate. In the batch physical foaming process, CO2 gas is dissolved in a polymer matrix under pressure. Then, the dissolved CO2 in the polymer matrix becomes supersaturated when the pressure is released. A certain degree of supersaturation produces CO2 bubbles in the polymer matrix. Bubbles are expanded by diffusion of the dissolved CO2 into the bubbles. The pressure release rate is one of the control factors determining number density of bubbles and bubble growth rate. To study the effect of pressure release rate on foaming, this paper developed a simple kinetic model for the creation and expansion of bubbles based on the model of Flumerfelt's group, established in 1996 [Shafi, M.A., Lee, J.G., Flumerfelt, R.W., 1996. Prediction of cellular structure in free expansion polymer foam processing. Polymer Engineering and Science 36, 1950-1959]. It was revised according to the kinetic experimental data on the creation and expansion of bubbles under a finite pressure release rate. The model involved a bubble nucleation rate equation for bubble creation and a set of bubble growth rate equations for bubble expansion. The calculated results of the number density of bubbles and bubble growth rate agreed well with experimental results. The number density of bubbles increased with an increase in the pressure release rate. Simulation results indicated that the maximum bubble nucleation rate is determined by the balance between the pressure release rate and the consumption rate of the physical foaming agent by the growing bubbles. The bubble growth rate also increased with an increase in the pressure release rate. Viscosity-controlled and diffusion-controlled periods exist between the bubble nucleation and coalescence periods. (c) 2008 Elsevier Ltd. All rights reserved.
机译：在有限的压力释放速率下，对聚丙烯（PP）/ CO2系统的间歇物理发泡过程进行了同时气泡成核和生长的模拟。在间歇式物理发泡过程中，CO2气体在压力下溶解在聚合物基质中。然后，当释放压力时，聚合物基质中溶解的CO 2变得过饱和。一定程度的过饱和会在聚合物基质中产生CO2气泡。气泡通过溶解的二氧化碳扩散进入气泡而膨胀。压力释放速率是确定气泡数密度和气泡生长速率的控制因素之一。为了研究压力释放速率对泡沫的影响，本文基于1996年建立的Flumerfelt小组的模型[Shafi，MA，Lee，JG，Flumerfelt，RW，1996]建立了一个简单的动力学模型，用于气泡的产生和膨胀。在自由膨胀聚合物泡沫加工中孔结构的预测。高分子工程与科学36，1950-1959]。根据在有限压力释放速率下气泡产生和膨胀的动力学实验数据对它进行了修改。该模型涉及用于气泡产生的气泡成核速率方程和用于气泡膨胀的一组气泡生长速率方程。气泡数密度和气泡生长速率的计算结果与实验结果吻合良好。气泡的密度随着压力释放率的增加而增加。模拟结果表明，最大气泡成核速率取决于压力释放速率与不断增长的气泡消耗物理发泡剂的消耗速率之间的平衡。气泡的增长率也随着压力释放率的增加而增加。在气泡成核和聚结阶段之间存在粘度控制和扩散控制的时期。 （c）2008 Elsevier Ltd.保留所有权利。

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