科研之友
微信
新浪微博
Facebook
分享链接
摘要
Nucleating agents have long been employed in polymeric foaming processes to promote cell nucleation, increase cell density, and improve cell uniformity This improvement in foam morphology is usually considered to result from the enhanced heterogeneous nucleation caused by the lower free energy barrier for cell nucleation However, less is known about the underlying mechanisms of nucleating-agent-enhanced nucleation In the polymer foaming process, pressure is a critical parameter that affects the degree of supersaturation of gas within a polymer-gas solution In most previous theoretical studies on cell nucleation, a uniform pressure was assumed throughout the solution Although this assumption may be acceptable when no particles have been added, its validity is questionable when nucleating agents are present It has been speculated that growing cells that have already been nucleated generate local flow fields that Induce tensile stresses around nearby particles, resulting in local pressure fluctuations The discontinuity at the Interface between a nucleating agent particle and the surrounding polymer melt yields local pressure and stress fields around the particle that are different from those in the bulk, which may enhance it as a potential heterogeneous nucleation site This paper presents a numerical analysis to investigate the pressure profile in the vicinity of nucleating agents and provides new information about the underlying mechanism that promotes cell nucleation in the presence of nucleating agents
- 出版日期2010-12-15
