【作者】 高峰；

【导师】 刘涛；

【作者基本信息】 华东理工大学 ， 化学工程， 2016， 硕士

【摘要】 以高密度聚乙烯（HDPE）和低密度聚乙烯（LDPE）熔融共混物为原料,超临界二氧化碳（scCO2）为物理发泡剂,通过挤出发泡的方法制备聚乙烯共混物的泡沫材料。系统研究了不同种类成核剂以及复合成核剂的成核效果,并通过对发泡结果、材料流变学性质、CO₂在聚合物中的溶解扩散性能以及聚合物的结晶性能进行分析,综合考察挤出发泡影响因素。结果表明,1.0 wt%滑石粉（talc）和1.0 wt%聚乙烯乙酸酯（PVAc）的复合成核剂发泡效果最佳,制备的聚乙烯共混物泡沫材料平均孔径可达254μm,孔密度6.6O×104 cells·cm-3,发泡倍率6.02。针对添加优选成核剂的HDPE/LDPE复合材料,优化其挤出发泡工艺,制备泡沫材料。结果表明：合适的模头温度（130。C）可以使熔体保持在适宜的剪切黏度范围内,有助于得到较好的泡孔形貌；随着进气量的增加,发泡倍率呈现线性增长趋势,泡孔直径下降,气量为0.8 mL·min-1,泡孔直径最小为217.5 μm,当气量超过1.2mL·min-1时,会出现较为明显的泡孔合并现象,进一步增加气量会造成流道不稳定。结合毛细管流变仪测试表明,温度上升以及CO₂进气量的增加都会降低PE的剪切黏度,且随着剪切速率的增加,剪切变稀现象更为明显。通过工艺条件优化,可以得到平均孔径217.5μ,泡孔密度为6.17m104cells·cm-3,表观密度为0.163 g·cm-3的PE发泡线材。更多还原

【Abstract】 In this work, high density polyethylene （HDPE） blending with low density polyethylene （LDPE） in a mass ratio of 7:3 were used as the raw materials, the supercritical carbon dioxide （scCO₂） as the physical blowing agent, and the nucleation effect of different nucleating agents was systematically studied by extrusion foaming. The results of foam, the rheology characterization, the solubility and diffusivity of CO₂ in composites and the crystal properties of polymer were used to analyze the effect of foam. The composite contained with 1.0wt% PVAc and 1.0wt% talc foamed best with the average cell size of 254 μm, cell density of 6.60×104 cells·cm-3 and expansion ratio 6.02.PE composites was used for extrusion foaming with scCO₂. The result showed that the proper die temperature kept the melt in the range of suitable shear viscosity, which helped to get good cell morphology. As the gas inlet increasing, the expansion ratio of PE foams increased linearly, as well as the cell size decreased. When the gas inlet was 0.8 mL·min-1, the cell size was smallest; when the gas inlet was higher than 1.2 mL·min-1, the cells got merged, and the flow was unstable with a much higher gas inlet. The shear viscosity was calculated by capillary rtheometer. It was shown that shear viscosity decreased when temperature and gas inlet increased. And shear thinning was more obvious as shear rate rose. With process optimization, the liner PE foams were produced with the apparent density of 0.163 g·em-3, cell density of 6.17×104 cells·cm-3 and average cell size of 217.5 μm.更多还原