【作者】 胡宏林；

【导师】 王荣国；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2012， 博士

【摘要】 聚合物基复合材料在使用过程中，受到外界荷载、温度等环境作用，材料内部会产生微裂纹。为了阻止微裂纹扩展，延长材料使用寿命，研究了两类不同修复机理的二元自修复材料，即基于阴离子引发链段聚合的环氧树脂二元自修复体系、基于加成聚合的环氧树脂二元自修复体系。开展了以微胶囊形式为载体，包覆环氧树脂及其阴离子固化剂和加成聚合型固化剂的研究，并运用液-液界面热力学的理论解释了液-液界面的稳定性对微胶囊的产率和性能的影响。无论采用何种微胶囊化方法，都需要形成一个具有两相界面的亚稳定体系，然后在连续相中加入可聚合或可成膜高分子，在分散相与连续相界面处聚合或沉降形成壳结构，最终微胶囊化。那么，乳液的稳定性将显著地影响着微胶囊的产率和性能。本文首先将界面热力学的原理应用到微胶囊化过程中，从热力学角度解释乳液稳定对微胶囊产率和质量的巨大影响。利用聚电解质自吸附的原理在油水界面层形成凝胶颗粒，促进乳液趋于稳定，成功合成了壳聚糖-脲醛树脂壁材微胶囊，并给出了微胶囊的最佳合成条件。此外，应用界面热力学理论解释了其他微胶囊化过程中，乳液稳定对微胶囊产率和性能的影响。其次，对环氧树脂微胶囊的合成原理、合成工艺以及性能进行了研究。通过原位乳液聚合法成功制备了包含环氧树脂及其活性稀释剂的脲醛树脂壁材微胶囊，给出了微胶囊的最佳合成条件。在此条件下合成的微胶囊具有最适宜制备自修复材料的物理性能。通过化学结构和物理结构分析，证明了微胶囊具有芯-壁结构，并证明了芯材具有反应活性。此外，微胶囊具有良好的热稳定性，在253℃以下可保持其化学稳定性。在此基础上，研究了基于阴离子引发链段聚合的环氧树脂微胶囊/DMP-30微胶囊二元自修复体系。其中固化剂的包覆是通过复相乳液法，制备了聚苯乙烯包覆阴离子催化剂DMP-30的微胶囊，对微胶囊的合成原理、合成工艺、表面形貌、粒径分布和平均粒径、化学结构、芯材抗渗透性、芯材活性、热稳定性进行了研究。通过化学结构和物理结构分析，证明了微胶囊具有芯-壁结构，并证明了芯材具有反应活性。但是，微胶囊在溶剂乙醇中的抗渗透性较差。此外，微胶囊在153℃以下可保持化学稳定性。最后，制备了掺杂环氧树脂微胶囊和DMP-30微胶囊的环氧树脂断裂韧性试样，测定修复效率，得出不同环氧树脂微胶囊含量和DMP-30微胶囊含量的条件下，随着DMP-30微胶囊含量和环氧树脂微胶囊含量的增加，自修复试样均呈现修复效率增加的现象。由于DMP-30微胶囊的抗渗透性较差，导致该体系的修复效率较低。环氧树脂/DMP-30二元自修复体系还有待于进一步研究，特别是在选择合适的芯材承载方式的方面。此外，还研究了基于阴离子引发链段聚合的环氧树脂微胶囊/2MZ-AZINE潜伏型固化剂二元自修复体系，制备了环氧树脂基自修复断裂韧性试样，测定其修复效率，试验结果表明：在较低微胶囊含量时，自修复效率对微胶囊含量的依赖性较差，一旦在某个小的修复单元内达到自修复的温度条件和2MZ-AZINE达到引发反应的最小值时，则会引发环氧树脂的开环聚合反应。此时，环氧树脂微胶囊和2MZ-AZINE的化学计量比对修复效率的影响较小，主要是受修复剂和固化剂在基体中的分布影响。确定了最佳的修复剂含量为15%的环氧树脂微胶囊和2%的2MZ-AZINE，其修复效率为~83%。并通过修复前后断裂面的SEM图片证明了成功实现了自修复过程。最后，研究了基于加成聚合的环氧树脂微胶囊/乙二胺微胶囊二元自修复体系。其中固化剂乙二胺的包覆是通过溶剂萃取与界面聚合相结合的方法，成功制备了环氧树脂-乙二胺壁材包覆乙二胺固化剂的微胶囊，对微胶囊的合成原理、合成工艺、化学结构、表面形貌、粒径分布和平均粒径、热稳定性、芯材活性进行了研究，并给出了最佳的合成条件。通过化学结构和物理结构分析，证明了微胶囊具有芯-壁结构以及芯材具有反应活性。微胶囊外观晶莹剔透呈规则球形，粘附少，且该方法所制备的微胶囊不需要考虑与环氧树脂基体之间的界面问题。此外，微胶囊在90℃以下可保持化学稳定性，但不可无限制的暴露于热环境中。最终制备了环氧树脂断裂韧性试样，测定其修复效率，试验结果表明：在较低环氧树脂微胶囊和乙二胺微胶囊含量时，自修复效率主要受到微胶囊在基体中的分布影响；在较高微胶囊含量时，主要是受到微胶囊含量的影响。最佳环氧树脂微胶囊与乙二胺微胶囊含量为12%和8%，呈现~80.4%的修复效率，并通过修复前后断裂面的SEM图片证明了成功实现了自修复过程。同时，对环氧树脂/DMP-30自修复体系、环氧树脂/2MZ-AZINE自修复体系和环氧树脂/乙二胺自修复体系，从制备工艺、修复机理和修复效率以及经济成本进行了对比研究。在自修复材料制备工艺方面，环氧树脂/DMP-30自修复体系和环氧树脂/乙二胺自修复体系采用的都是双微胶囊体系，对材料的力学性能损伤较大；环氧树脂/2MZ-AZINE自修复体系采用的是单微胶囊体系，对材料的力学性能损伤相对较小。在修复机理和修复效率方面，环氧树脂/DMP-30自修复体系、环氧树脂/2MZ-AZINE自修复体系均为阴离子引发环氧开环聚合的机理，较少的固化剂含量即可实现固化；环氧树脂/乙二胺自修复体系是基于加成聚合的环氧树脂二元自修复体系，修复效率与环氧树脂微胶囊含量与乙二胺微胶囊含量在一定含量范围内存在依赖关系。在经济成本方面，环氧树脂/DMP-30自修复体系的成本相对较高。更多还原

【Abstract】 Microcracks are inevitably generated during the use of structural polymericcomposite when affected by the environmental factors such as outside load andtemperature. We designed two different kinds of binary self-healing polymericmaterials, which are based on anionic chain polymerization and additionpolymerization of epoxy and its curing agent, in order to prevent microcrackspropagating and prolong using life. Microencapsulation of epoxy resin and itshardeners were investigated respectively. Also, effect of stabilization of liquid-liquidinterface of oil-water emulsion on microcapsule’s yield and properties wereinterpreted through the theory of interface thermodynamics.A metastable emulsion system of liquid-liquid interface is essential formationfor all microencapsulation. Then shell material former polymerized at the interfacebetween dispersed phase and continuous phase, forming microcapsules. Therefore,the stabilization of emulsion would greatly influence on microcapsule’s yield andproperties. First of all, in this paper, the theory of interface thermodynamics wasapplied in microencapsulation process to explain the effect of stabilization ofemulsion on yield and properties of microcapsules. For the application example, wesuccessfully prepared chitosan-(urea formaldehyde) shell microcapsule usingparticle-stabilized emulsion by an interfacial gel layer which is self-assembled byelectrostatic adsorption between negatively charged surfactant SDS and positivelycharged polysaccharide chitosan in an oil-in-water emulsion. Finally, the optimumconditions for preparing microcapsules were concluded. Additionally, the theory ofinterface thermodynamics were also applied in other microencapsulation process inthis paper.Secondly, we investigated synthetic principle, synthesis condition and propertiesof epoxy-containing microcapsules. Microcapsules were synthesized by in situpolymerization of urea and formaldehyde in an emulsion. The optimum conditionsfor preparing microcapsules were concluded. Under the optimum conditions,resultant microcapsules possess adequate physical properties for application in self-healing materials. The core-shell structure of microcapsule was proved by FT-IR,OM and SEM. The reactivity of core material was proved by DSC. Besides,microcapsules possess good thermal stabilization, which can keep chemicalstabilization under253℃.On this basis, binary self-healing material based on anionic chainpolymerization of epoxy resin and DMP-30was developed. DMP-30-containingmicrocapsules were prepared by solvent evaporation method. The synthetic principle,synthesis process, surface morphology, size distribution and average diameter, chemical structure, core anti-permeability, reactivity of core material and thermalstabilization were investigated. The core-shell structure and core reactivity ofmicrocapsules were proved, but the anti-permeability of microcapsules in ethanolsolvent was poor. Otherwise, microcapsules can keep chemical stabilization under153℃. Finally, self-healing samples with epoxy-containing microcapsules and DMP-30-containing microcapsules were fabricated, and self-healing efficiency was testedby fracture toughness before and after healing process. The results shows that self-healing efficiency increases with the enhancement of content of microcapsules.Unfortunately, healing efficiency of this system is lower because of the poor anti-permeability of microcapsules. This system needs further investigation, especially onthe suitable carrier of core material.Besides, we also investigated binary self-healing system with epoxy-containingmicrocapsule and latent hardener2MZ-AZINE based on anionic chainpolymerization. Self-healing samples were prepared for measuring healing efficiency.It is worth noting that although healing efficiency increases with a rise inmicrocapsules content in the regime of low microcapsules content, the former isnearly independent of microcapsules content above a certain value. Once dosage of2MZ-AZINE reaches the prescribed minimum, anionic chain polymerization of thereleased epoxy begins at certain temperature. The requirement of stoichiometriccomposition at every inch of repair region is unnecessary. Therefore, the distributionof microcapsules and latent curing agent greatly influences the healing efficiency. Asa result, the optimal weight ratio of microcapsules and curing agent2MZ-AZINEembeded in the epoxy matrix are15wt%and2wt%, and the healing efficiency is~83%. The SEM photos of fracture surface before and after healing process provedthat healing process was successfully realized.At last, we investigated binary self-healing system with epoxy-containingmicrocapsule and ethylenediamine(EDA)-containing microcapsule based on additionpolymerization. EDA-containing microcapsules were successfully prepared bycombining solvent extraction method with interfacial polymerization method. Thesynthetic principle, synthesis process, chemical structure, surface morphology, sizedistribution and average diameter, thermal stabilization and reactivity of corematerial were investigated. The optimum conditions for preparing microcapsuleswere concluded. The core-shell structure and core reactivity of microcapsules wereproved. The appearance of resultant microcapsule was transparent, spherical and lessadhesion. The interface performance between microcapsules and matrix wasunnecessary to be considered because of the epoxy-EDA shell material when used inan epxoy-based composite. Additionally, microcapsules can keep chemicalstabilization under90℃, but unlimited exposure under thermal environment will leadto the increase of weight loss of core material. Finally, self-healing samples wereprepared for measuring healing efficiency. At lower content of epoxy-containing microcapsules and EDA-containing microcapsules, healing efficiency was mainlyinfluenced by distribution of both microcapusles in the matrix. At higher content ofboth microcapsules, content of both microcapsules was to be the main factor thatinfluenced the healing efficiency. As a result, the optimal weight ratio of epoxy-containing microcapsules and EDA-containing microcapsules embeded in the epoxymatrix are12wt%and8wt%, offering~80.4%healing efficiency. The SEM photosof fracture surface before and after healing process proved that healing process wassuccessfully realized.Additionally, epoxy/DMP-30self-healing system, epoxy/2MZ-AZINE self-healing system and epoxy/EDA self-healing system were comparatively investigatedat the aspect of preparation process, healing mechanism, healing efficiency andeconomic cost. In preparation process, we adopted double-microcapsule system onepoxy/DMP-30and epoxy/EDA self-healing system, which largely damaged themechanical performance of material. But epoxy/2MZ-AZINE self-healing systemwas adopted by single-microcapsule system, which weakly effected on themechanical performance of material compared with double-microcapsule system. Inhealing mechanism and healing efficiency, epoxy/DMP-30and epoxy/2MZ-AZINEself-healing system is based on anionic chain polymerization, which inferred that lesshardner content could initiate the polymerization. The epoxy/EDA self-healingsystem is based on addition polymerization, which inferred that content of thehealing agent largely influenced the healing efficiency at a certain range. Ineconomic cost, the expenditure of epoxy/DMP-30self-healing system is the most one.更多还原