矩形截面微模具通道中熔体的黏性耗散效应

Viscous dissipation effect of polymer melt in a rectangular cross section micro mold channel

基于对微注塑成型过程中聚合物熔体充模流动时黏性耗散效应的理论分析,以聚丙烯(PP)和高密度聚乙烯(HDPE)两种聚合物材料,在不同工艺参数作用下流经不同当量直径和长径比矩形截面微模具通道时,由黏性耗散效应引起的微通道中熔体温度变化进行了试验测量和数值模拟。结果显示,微通道出口熔体温度的试验测量和数值模拟值与理论计算值非常吻合,且其平均误差小于1℃。同时研究发现,增大微模具通道当量直径和长径比时,熔体流动时的黏性耗散热量增多,通道出口熔体温度升高;而当微通道几何尺寸一定时,其黏性耗散热量随注射速度和注射压力的升高而增加,随熔体温度和模具温度的升高而降低;但同样试验条件下,对剪切作用敏感性强的PP材料的黏性耗散热量明显高于对剪切敏感性弱的HDPE材料。

Based on the theoretical analysis of viscous dissipation effect when polymer melt flowing in micro injection mold, the change of the melt temperature of the polypropylene （PP） and high density polyethylene （HDPE） caused by the viscous dissipation effect were tested and simulated in the rectangular cross section micro channels with different equivalent diameters and ratios of length to diameter under a variety of process parameters. The results showed that the theoretical calculation and numerical simulation values were highly consistent with the test results, and the average errors were all less than 1 ℃. The study found that when the equivalent diameter and ratios of length to diameter were increased, the heat of viscous dissipation increased, thus the outlet temperature of channel rose. When the geometry size of the micro channels remains unchanged, the viscous dissipation heat increased with the increase of the injection speed and injection pressure, and decreased with the increase of the melt temperature and mold temperature. But under the same test condition, the viscous dissipation heat of PP material which is more sensitive to shear was obviously higher than that of HDPE.