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摘要本文尝试通过引入短碳纤文来改善聚丙烯发泡的泡孔结构。为了提高短碳纤文的成核能力，借助打浆造纸法预先得到短碳纤文和聚丙烯的共混物。然后通过双螺杆微量挤出机将共混物熔融挤出，并注射成型获得短碳纤文/聚丙烯复合材料。选取碳纤文的含量为5wt%、15wt%和25wt%，通过SEM对碳纤文在聚丙烯中的分布情况进行表征，发现打浆造纸法可以得到碳纤文分布均匀的复合材料；并通过DSC，得到了复合材料的结晶度和熔点；从DMA测试中，知道当碳纤文的含量增大到25wt%时，复合材料的模量得到较大幅度的提升。
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通过分步升温法对复合材料进行CO2溶解度和发泡性能研究。结果显示，CO2在聚丙烯的溶解度和复合材料的结晶度紧密关联，结晶度越大，CO2的溶解量就越小；随着碳纤文含量的增加，泡孔密度也随之增加，这表明随着碳纤文含量的增加，微孔材料在发泡过程中主要是异相成核，碳纤文与聚丙烯纤文界面之间相互作用较弱，为复合材料泡孔的形成提供了成核位点。8658
关键词: 聚丙烯，复合材料，短碳纤文，发泡，超临界CO2
毕业设计说明书（论文）外文摘要
Title Preparation of short carbon fiber/polypropylene
fine-celled foams in supercritical CO2
Abstract
This article reported an attempt to improve polypropylene (PP) fine-celled foaming with the incorporation of short carbon fibers (CFs). The CFs with uniform dispersion in PP matrix were obtained in reference to the way of papermaking. The composites were prepared via melt compounding in a twin-screw extruder followed by injection molding. Three concentrations of carbon fibers (CFs), 5, 15 and 25wt%, were used. From the SEM, it was observed that the dispersion of CFs was improved. In other words, the way of papermaking can solved the dispersion problem of CFs. The crystallinity and melting points of composites were obtained from the DSC curves. It was also found from the DMA that the viscoelastic of the composites with 25 wt% CFs contents increased significantly.
The foaming was carried out by a batch process with supercritical CO2 as the physical blowing agent. The CO2 absorption and the foamability of composites were investigated. The results showed that the CO2 dissolved in the matrix was tightly related to the crystallinity of composites. The larger the crystallinity was, the lower the CO2 dissolved was. And the increment in the cell density with increasing CFs content indicated that the bubble nucleation was dominated by the heterogeneous mechanism with the addition of CFs. The poorly bonded interface between CFs and PP could serve well as nucleation sites.
Keyword: Polypropylene; Composites; Short carbon fiber; foam; supercritical CO2
目 次
1 绪论 1
2 实验部分 3
2．1 实验药品和设备 3
2．2 样品制备 4
2．3 CO2溶解度测定方法 4
2．4 超临界发泡的基本过程 6
2．5 性能测试与结构表征 7
3 结果与讨论 8
3.1不同碳纤文含量的聚丙烯/碳纤文复合材料对结晶度的影响 8
3.2碳纤文在聚丙烯中的分散情况 9
3.3动态力学性能 10
3.4超临界CO2在聚合物中的溶解量 11
3.5碳纤文含量对碳纤文/聚丙烯发泡材料泡孔形态的影响 13
3.6饱和压力对碳纤文/聚丙烯发泡材料泡孔形态的影响 15
结 论 18
致 谢 19
参 考 文 献 20
1 绪论
微孔聚合物是指泡孔尺寸从一微米到几十微米的多孔聚合物材料，与一般的泡沫塑料毫米级的泡孔相比，微孔聚合物的泡孔要小得多，而泡孔密度要大得多，因而称为微孔聚合物[1]。与泡沫塑料的分类相同，微孔聚合物也有开孔和闭孔两种形式，如闭孔型微孔聚合物可应用于汽车零部件、运动器材、食品包装和微电子等要求材料质量轻、力学性能高和热稳定性高的场合；而开孔型微孔聚合物则可应用于膜分离、离子交换树脂、吸附、吸音、过滤和组织工程支架材料等领域，因此微孔发泡材料被认为是2l世纪的新型材料[2]。