【作者】 李春艳；

【导师】 何继敏；

【作者基本信息】 北京化工大学 ， 机械设计及理论， 2008， 硕士

【摘要】 泡沫塑料是一种性能卓越的聚合物/气体复合材料,具有许多优异性能,用途很广,已遍及各行各业。泡沫塑料中的结构发泡塑料具有不发泡或少发泡的皮层,这不仅使泡体表面光滑平整,而且其力学性能明显优于自由发泡塑料,使得泡沫塑料的应用更加广泛。挤出结构发泡成型最早出现于60年代,应用于聚氯乙烯（PVC）挤出结构发泡仿木材料。目前,PVC挤出结构发泡成型技术比较成熟。鉴于PVC挤出结构发泡成型的研究技术日益成熟,其它塑料挤出结构发泡成型也相应地受到了关注。由于聚丙烯（PP）树脂密度低,力学性能优异,其泡沫产品可回收性好,有利于环保,其挤出结构发泡成型趋势看好。但是,PP适合发泡的温度范围非常窄,熔体强度低,发泡过程很难控制。针对这一情况,本文对PP挤出增强结构发泡成型进行了研究。根据塞路卡法结构发泡原理,专门设计了适用于PP挤出结构发泡的成型机头,实现了PP挤出结构发泡,制得了具有光滑坚硬结皮,发泡芯层的结构发泡试样。通过添加增强材料,进一步改善了试样的力学性能,获得了PP挤出增强结构发泡试样。通过大量的实验,从宏观性能及微观结构两方面,重点研究了配方、工艺参数对PP挤出增强结构发泡成型的影响。本文通过对发泡剂及助发泡剂的实验研究获得了较好的配方比例;通过加入高熔体强度聚丙烯（HMSPP）、低密度聚乙烯（LDPE）及三元乙丙橡胶（EPDM）对PP进行共混改性,提高其熔体强度,改善了发泡效果,减小了泡孔尺寸,增大了泡孔密度;通过添加玻纤改性PP母粒,对PP挤出结构发泡试样进行了增强。结果表明:在其它配方组分固定的基础上,与未添加增强材料的试样相比,随着玻纤改性PP母粒含量的增加,试样的泡孔尺寸变大,泡孔密度减小,但表观密度逐渐减小,力学性能显著提高。合适的机头温度及螺杆转速下可以获得较好的结构发泡试样。通过研究配方及工艺参数对PP挤出结构发泡的影响,获得了本研究的最佳配方及工艺参数。配方为:LDPE含量为15份,EPDM含量为5份,玻纤改性PP母粒含量为15份,发泡剂含量为2.0份,助发泡剂含量为0.025份,成核剂为0.1份;工艺参数为:机头温度为160℃,螺杆转速20r·min^-1,机头压力为12.5MPa。在此条件下能获得具有较好微观结构及宏观性能的PP挤出增强结构发泡试样。试样的拉伸强度、冲击强度及弯曲模量分别提高了44.1%、56.8%及16.3%。本论文的研究成果,为PP挤出增强结构发泡成型技术的工业化开发提供了理论依据和经验。更多还原

【Abstract】 Foamed plastic is a kind of polymer/gas composites material which has outstanding performances. It is widely used in every walk of life for its excellent performance. Structural foam plastic belongs to foamed plastic and it has cortex without foam or less foam, which makes it not only has smooth surface but also has better mechanical properties than free foamed plastic. All that makes foamed plastic is used much widely.Structural foam extrusion appeared as early as 1960’s and it was firstly used for polyvinyl chloride （PVC） novel imitation wood. At present, PVC structural foam extrusion technology is more mature. Other plastics structural foam extrusion is also got attention. Polypropylene （PP） structural foam extrusion is got more attention for its low density, excellent mechanical properties, nice degradation and recycling. However, PP foam process is difficult to control for its narrow temperature range and low melt strength.Reinforced PP structural foam extrusion was researched in this paper. An extruder die was designed especially for PP structural foam extrusion according to Celuka principle. The die had achieved structural foam and PP structural foam products were got. Reinforced PP structural foam products which had improved mechanical properties were got with modified PP by glass fiber. A lot of experiments were made using the die. Effects of formula and process parameters on reinforced PP structural foam extrusion were mainly researched through both macroscopic properties and microstructure.In this paper, better formula proportion was gained based on experiments using foaming agent and auxiliary foaming agent. Melt strength was improved, foam size was decreased and foam density was increased through blending modification with high melt strength polypropylene （HMSPP）, low density polyethylene （LDPE） and ethylene propylene diene monomer （EPDM）. Reinforced PP structural foam products were got adding modified PP by glass fiber to reinforce PP. Comparing with products without modified PP by glass fiber, as the increasing of modified PP by glass fiber content, the foam size increased and the foam density decreased, but the apparent density got lower and the mechanical properties improved significantly. Better products could be got with suitable die temperature and screw rotation speed.Based on the experiments, the optimal formulation was got with the contents of LDPE, EPDM, modified PP by glass fiber, foaming agent, auxiliary foaming agent, nucleating agent corresponding to 15 portions, 5 portions, 15 portions, 2.0 portions, 0.025 portions and 0.1 portions, respectively. The products with better macroscopic properties and microstructure could be got under the conditions of die temperature, screw rotation speed, die pressure corresponding to 160℃, 20rmin^-1 and 12.5MPa, respectively. Comparing with products without modified PP by glass fiber, tensile strength, impact strength and flexural modulus of the products were increased by 44.1%, 56.8% and 16.3%, respectively.The research results of the paper provide theory and experience for the industrial development of reinforced PP structural foam extrusion.更多还原