【作者】 朱光明；

【导师】 梁国正；

【作者基本信息】 西北工业大学 ， 材料学， 2004， 博士

【摘要】 聚己内酯（PCL）是一种新型可生物降解性高分子材料,并具有良好的生物相容性,在工农业生产及生物医学工程等领域具有十分重要的应用价值。但PCL的一个严重缺陷是它的熔点较低,只有60℃左右,因此,耐热变形性能非常差。作者尝试利用高能辐射对PCL进行处理来提高PCL的耐热性、强度、尺寸稳定性,并赋予PCL形状记忆特性。 本文首先研究了不同分子量的PCL在不同温度条件下的辐射交联规律及γ-辐照对不同分子量的PCL的力学性能、热性能、结晶行为的影响,在此基础上,研究了辐射交联后的PCL的形状记忆行为。研究结果表明,PCL的分子量越大,辐射交联所需的凝胶化剂量越低。溶胶分数S+S^1/2与1/D的关系很好地符合Charlesby-Pinner关系式,说明PCL的辐射交联属于无规交联。提高温度有利于PCL的辐射交联,温度越高,凝胶化剂量降低,辐射交联G_C增加,裂解与交联比率降低。辐射剂量对PCL的力学性能影响显著,剂量越大,拉伸强度和断裂伸长率下降越多,但分子量较高的PCL的拉伸强度受剂量的影响较小。DMA分析表明,PCL辐照交联后的弹性模量和耐热性能显著提高。交联度较高的PCL表现出高弹态,可以拉伸。DSC分析表明,辐射交联使PCL的结晶度有所增加,但也使结晶熔点有所降低。适度交联（凝胶含量>10%）的PCL具有良好的形状记忆功能,形变恢复率可达到100%;形变恢复速率和辐射交联程度有关,交联度越大,形变恢复越快;形变恢复温度和PCL的熔点相关,约在52～60℃之间。 分别从聚集态结构、化学热力学及Maxwell-Wiechert粘弹模型对辐射交联PCL产生形状记忆效应的原理进行了分析和论证。 其次,研究了聚酯丙烯酸酯（PEA）类多官能团物质对PCL的强化辐射交联效应。分别研究了PEA的用量、PEA的官能团数目、辐射剂量等因素对PCL的辐射交联规律、力学性能、动态机械性能、结晶动力学行为、形状记忆行为等性能的影响。研究结果表明,添加PEA后的PCL的辐射交联规律不再遵从Charlesby-Pinner关系式,而是符合陈欣方-刘克静-唐敖庆公式。PEA的加入可以显著提高PCL辐射交联的效率,相同剂量时,官能团数目越多、用量越大的样品,生成的凝胶含量越多,强化辐射交联效应越大,强化交联PCL的拉伸强度提高。据此对多官能团物质强化辐射交联的机理进行了分析和讨论。 强化辐射交联PCL的动态力学分析表明,随着PEA用量及辐射剂量的增加,其弹性模量升高。强化交联的PCL样品在其熔点以上都呈现出高弹态平台,更多还原

【Abstract】 The characteristics of radiation crosslinking and shape-memory behaviors for polycaprolactone (PCL) and its blends were investigated systematically in this dissertation. Firstly, PCLs with different molecular weight were cross-linked by Y -radiation at different temperature conditions. The radiation cross-linking feature was examined by Soxhlet extractor with toluene and analyzed using Charlesby-Pinner equation. It was concluded that the cross-linking degree was relative to molecular weight and radiation dose, and, the relation between sol fraction and dose followed the Charlesby-Pinner equation. The higher temperature is useful to radiation crosslinking, the higher the temperature, the lower gelation dose, radiation crosslinking Gc increases, po/qo decreases. Radiation caused the tensile strength and elongation of all the samples drop. The DSC diagrams demonstrated that radiation caused the crystallinity increased and the melting temperature of PCL decreased. The DMA analysis indicated that radiation cross-linking raised heat deformation temperature of PCL and presented a rubbery state, whereas rendered enough strength at temperatures higher than melting point and provided enough force to recover the deformation. The shape memory results revealed that only those specimens that had a sufficiently high cross-linking degree (gel content is higher than about 10%) were able to show the typical shape memory effect, a large recoverable strain, and a high final recovery rate. The response temperature of the recovery effect (about 55℃) was related to the melting point of the samples.The mechanism of shape memory effects of radiation crosslinking PCL was analysed and demonstrated from the structure of assemble state, chemical thermodynamics and Maxwell-Wiechert viscoelastic model.Secondly, the enhanced effects of polyfunctional polyester acrylate(PEA) on radiation crosslinking of PCL were studied. The influences of the usage of PEA, the size of functional group, radiation dose on radiation crosslinking law, dynamic mechanical properties, crystallization, shape memory behaviors of PCL were investigated, respectively. It was proved that radiation crosslinking of PCL after applying PEA wasn’t in correspondence with the classic Charlesby-Pinner equation, but followed Chen-Liu-Tang relation. The efficiency of radiation crosslinking of PCL was distinctively improved after applying PEA. The more the usage andfunctional group number, the more gel content and the more distinctive the radiation crosslinking effects. On the basis of this, the mechanism of enhancing radiation crosslinking of PEA was proposed and discussed. The DMA analysis indicated that enhanced radiation cross-linking better raised heat deformation temperature of PCL. The shape memory results revealed that the enhanced crosslinked PCL presented 100% recoverable deformation and more quick recovery rate. The nonisothermal crystallization kinetics analysis demonstrated that the way of crystalline growth of radiation crosslinked PCL belonged to heterogeneous nucleation and single-dimension growth model. By using an evaluation method proposed by Kissinger, activation energies of nonisothermal crystallization for radiated PCLs with different radiation dose have been evaluated to be between 64 kJ/mol and 54 kJ/mol.Lastly, the radiation crosslinking of PCL and polydimethylvinylsiloxane (PDMVS) blends was also studied. It was concluded that the radiation crosslinking of PCL/PDMVS) blends also followed Charlesby-Pinner equation. PDMVS played a promoting role in crosslink reaction during radiation. As the usage of PDMVS increases, the gelation dose and the ratio of degradation to cross-linking (po/qo) decreases, the efficiency of radiation crosslinking is raised. The Yong’s modulus of radiation crosslinked PCL/PDMVS blends decreases with the increase of PDMVS under the melting point temperature of PCL, and increases with the increase of PDMVS above the melting point temperature of PCL. The properly crosslinked PCL/PDMVS blends exhibited fine shape memory effects, the ratios of deformation recovery is above 95%.更多还原