超高分子量聚乙烯及其纳米复合材料的链缠绕结构调控
发布时间：2019-07-03 12:29
【摘要】：超高分子量聚乙烯(UHMWPE)是指分子量超过100万g/mol的高密度聚乙烯。由于其制品具有其它材料无可比拟的耐冲性、耐磨性、自润滑性和耐化学腐蚀等特性,目前已经被广泛的应用于民用、军用等各个领域。目前加工UHMWPE的常用方法主要有挤出成型法、模压成型法和注塑成型法等方法。但是,由于商用的UHMWPE的分子量大、链缠结高,使得加工过程耗能巨大,且污染严重。于是,从根本上减少UHMWPE基体粉料的缠结度,从而降低加工难度,以期达到绿色加工的目的,是生产UHMWPE的重要研究方向。本论文基于“通过加入不同种类的多面齐聚倍半硅氧烷(Polyhedral oligomeric silsesquioxane,POSS)纳米粒子,改变催化剂的聚合环境,从而构建与活性中心特性相宜的链段生长环境”的研究思想,围绕制备无缠结UHMWPE纳米复合材料,进行了如下四个方面的工作:(1)极性POSS粒子对UHMWPE链缠绕的调控;(2)非极性POSS粒子对UHMWPE链缠绕的调控;(3)极性POSS粒子对UHMWPE链段结晶行为的影响;(4)小分子聚合物对UHMWPE链缠绕的影响。具体的工作及主要研究成果如下:(1)通过化学负载将FI催化剂铆钉在POSS上,从而改变的催化剂的聚合环境,并通过控制聚合时间得到了不同缠结状态的UHMWPE纳米复合材料。研究表明:FI催化剂通过化学负载的方式结合在POSS表面,且通过乙烯的原位聚合,POSS粒子能够被均匀的分散在UHMWPE基体中。同时,我们得到了无缠结的UHMWPE纳米复合材料。最后,POSS粒子能够加强UHMWPE基体的热稳定性和吸水性。(2)通过物理负载,使不同种类的非极性烷基POSS调节FI催化剂的聚合环境,来达到调节UHMWPE缠结度的目的。研究表明:能够在甲苯中完全分散的甲基-POSS在UHMWPE中获得了最好的分散程度。通过结晶动力学和流变学的研究,我们可以知道环己基-POSS相对于甲基-POSS和苯基-POSS最能使UHMWPE基体趋于无缠结。(3)为了探明极性POSS影响UHMWPE链段缠结的机理,我们对具有相似分子量基体的UHMWPE的结晶行为进行了研究。从等温和非等温结晶动力学研究中,我们看到:POSS在UHMWPE结晶过程中更多的扮演了成核剂的角色,由于POSS的加入可以增加UHMWPE链段结晶的速率,从而得到了无缠结的UHMWPE纳米复合材料。(4)基于制备能够合成双峰聚乙烯的复合型催化剂,使得在聚合过程中使小分子聚合物原位的调节大分子量的UHMWPE的缠结程度。研究表明:我们制得了无缠结的UHWMPE复合材料,且当聚合介质为甲苯时,样品最倾向于无缠结状态。
[Abstract]:Ultra-high molecular weight polyethylene (UHMWPE) refers to high density polyethylene (HDPE) with a molecular weight of more than 1 million g / mol. Because of its unparalleled impact resistance, wear resistance, self-lubrication and chemical corrosion resistance, its products have been widely used in civil, military and other fields. At present, the common methods of processing UHMWPE are extrusion forming method, molding method and injection molding method. However, due to the large molecular weight and high chain entanglement of commercial UHMWPE, the processing process consumes a lot of energy and pollutes seriously. Therefore, it is an important research direction of UHMWPE production to fundamentally reduce the entanglement of UHMWPE matrix powder, so as to reduce the processing difficulty in order to achieve the purpose of green processing. Based on the research idea of "changing the polymerization environment of catalyst by adding different kinds of polyhedral oligomerized silsesquioxane (Polyhedral oligomeric silsesquioxane,POSS nanoparticles to construct the segment growth environment suitable for the characteristics of active center", the following four aspects of preparation of unentangled UHMWPE nanocomposites were carried out: (1) the regulation of polar POSS particles on UHMWPE chain winding; (2) the regulation of non-polar POSS particles on UHMWPE chain winding, (3) the effect of polar POSS particles on the crystallization behavior of UHMWPE segments, and (4) the effect of small molecular polymers on UHMWPE chain winding. The specific work and main research results are as follows: (1) the rivets of FI catalyst were loaded on POSS by chemical loading, thus changing the polymerization environment of the catalyst, and the UHMWPE nanocomposites with different entanglement states were obtained by controlling the polymerization time. The results show that the FI catalyst is bound to the POSS surface by chemical support, and the POSS particles can be uniformly dispersed in the UHMWPE matrix through the in-situ polymerization of ethylene. At the same time, we obtained UHMWPE nanocomposites without entanglement. Finally, POSS particles can enhance the thermal stability and water absorption of UHMWPE matrix. (2) different kinds of non-polar alkyl POSS can adjust the polymerization environment of FI catalyst by physical loading, so as to adjust the degree of UHMWPE entanglement. The results show that methyl-POSS, which can be completely dispersed in toluene, has the best dispersion degree in UHMWPE. Through the study of crystallization kinetics and Rheology, we can know that Cyclohexyl-POSS can make UHMWPE matrix tend to be unentangled compared with methyl-POSS and phenyl-POSS. (3) in order to find out the mechanism of polar POSS affecting UHMWPE segment entanglement, we have studied the crystallization behavior of UHMWPE with similar molecular weight matrix. From the study of Isomild non-Isothermal crystallization kinetics, we can see that POSS plays a more important role as nucleating agent in the crystallization process of UHMWPE. Because the addition of POSS can increase the crystallization rate of UHMWPE segment, the unentangled UHMWPE nanocomposites are obtained. (4) based on the preparation of composite catalysts which can synthesize bimodal polyethylene, In the process of polymerization, the small molecule polymer can adjust the entanglement degree of UHMWPE with large molecular weight in situ. The results show that the unentangled UHWMPE composites are prepared, and when the polymerization medium is toluene, the samples are most inclined to be unentangled.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O632.12;TB33
本文编号：2509384
[Abstract]:Ultra-high molecular weight polyethylene (UHMWPE) refers to high density polyethylene (HDPE) with a molecular weight of more than 1 million g / mol. Because of its unparalleled impact resistance, wear resistance, self-lubrication and chemical corrosion resistance, its products have been widely used in civil, military and other fields. At present, the common methods of processing UHMWPE are extrusion forming method, molding method and injection molding method. However, due to the large molecular weight and high chain entanglement of commercial UHMWPE, the processing process consumes a lot of energy and pollutes seriously. Therefore, it is an important research direction of UHMWPE production to fundamentally reduce the entanglement of UHMWPE matrix powder, so as to reduce the processing difficulty in order to achieve the purpose of green processing. Based on the research idea of "changing the polymerization environment of catalyst by adding different kinds of polyhedral oligomerized silsesquioxane (Polyhedral oligomeric silsesquioxane,POSS nanoparticles to construct the segment growth environment suitable for the characteristics of active center", the following four aspects of preparation of unentangled UHMWPE nanocomposites were carried out: (1) the regulation of polar POSS particles on UHMWPE chain winding; (2) the regulation of non-polar POSS particles on UHMWPE chain winding, (3) the effect of polar POSS particles on the crystallization behavior of UHMWPE segments, and (4) the effect of small molecular polymers on UHMWPE chain winding. The specific work and main research results are as follows: (1) the rivets of FI catalyst were loaded on POSS by chemical loading, thus changing the polymerization environment of the catalyst, and the UHMWPE nanocomposites with different entanglement states were obtained by controlling the polymerization time. The results show that the FI catalyst is bound to the POSS surface by chemical support, and the POSS particles can be uniformly dispersed in the UHMWPE matrix through the in-situ polymerization of ethylene. At the same time, we obtained UHMWPE nanocomposites without entanglement. Finally, POSS particles can enhance the thermal stability and water absorption of UHMWPE matrix. (2) different kinds of non-polar alkyl POSS can adjust the polymerization environment of FI catalyst by physical loading, so as to adjust the degree of UHMWPE entanglement. The results show that methyl-POSS, which can be completely dispersed in toluene, has the best dispersion degree in UHMWPE. Through the study of crystallization kinetics and Rheology, we can know that Cyclohexyl-POSS can make UHMWPE matrix tend to be unentangled compared with methyl-POSS and phenyl-POSS. (3) in order to find out the mechanism of polar POSS affecting UHMWPE segment entanglement, we have studied the crystallization behavior of UHMWPE with similar molecular weight matrix. From the study of Isomild non-Isothermal crystallization kinetics, we can see that POSS plays a more important role as nucleating agent in the crystallization process of UHMWPE. Because the addition of POSS can increase the crystallization rate of UHMWPE segment, the unentangled UHMWPE nanocomposites are obtained. (4) based on the preparation of composite catalysts which can synthesize bimodal polyethylene, In the process of polymerization, the small molecule polymer can adjust the entanglement degree of UHMWPE with large molecular weight in situ. The results show that the unentangled UHWMPE composites are prepared, and when the polymerization medium is toluene, the samples are most inclined to be unentangled.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O632.12;TB33
【参考文献】
相关期刊论文 前1条
1 杨挺;程丽鸿;钱丹;;我国聚乙烯发展现状及市场分析[J];绝缘材料;2013年03期
，本文编号：2509384
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