【作者】 王大明；

【导师】 陈春海；

【作者基本信息】 吉林大学 ， 精细化学品化学， 2010， 博士

【摘要】 本文采用双酚A型二醚二酐(BPADA)和3-乙炔基苯胺(APA)合成了一种乙炔基封端的聚酰亚胺预聚体,通过引入柔性醚键基团和异丙基结构使得该预聚体具有较低的熔融加工温度,从而赋予此类乙炔基封端聚酰亚胺预聚物较宽的加工窗口,同时还保证交联后具有较高的耐热性。为了进一步拓宽该种乙炔基封端的聚酰亚胺预聚物作为高性能复合材料树脂基体的应用,本论文利用不同结构的热塑性高聚物对其进行了增韧改性研究,详细的研究了不同热塑相结构、不同混合方式,不同的添加量以及不同混合方式与增韧效果的关系,并分析总结了不同相态结构与增韧效果的对应关系。热塑性树脂首先选择了工艺性良好的含氟可溶性聚芳醚酮(6F-PAEK)对基体树脂进行增韧改性,通过控制混合条件得到了不同的相形态。但6F-PAEK自身较低的玻璃化转变温度和热失重温度严重限制了这种增韧剂体系的应用。因此我们又合成了四种结构不同、耐热等级与基体树脂更匹配的热塑性聚酰亚胺树脂。分别为:3,3′,4,4′-联苯四酸二酐(s-BPDA)和4.4‘-二氨基二苯醚(ODA);双酚A型二醚二酐单体(BPADA)和ODA;3,3’,4,4’-二苯醚四酸二酐(ODPA)和ODA;1,4-双-(4‘-氨基苯氧基)-2-(苯基)苯(p-TPEQ)和s-BPDA合成了四种热塑性聚酰亚胺高聚物。这几种热塑性聚酰亚胺高聚物含有不同比例的柔性基团,分子链的柔性不同。研究结果发现,加入热塑性增韧剂后韧性都得到了提高,这与相形态有密切关系,同时分子链柔性对增韧有明显的影响,柔性基团越多,增韧效果越好,而且所有体系的热性能基本没有受到影响。同时利用聚酰亚胺高聚物(p-TPEQ和s-BPDA)考察了不同溶剂对共混体系的影响,结果表明低沸点溶剂对于增韧效果及热学性质改善优于高沸点溶剂,并且对相形态的控制上也略胜一筹。确定最佳增韧体系与增韧条件后,利用增韧后的树脂为基体树脂与碳纤维复合制备了复合材料层压板,利用C扫和CAI值测量比较,并通过对形貌的研究发现层间开裂现象得到了缓解,树脂和纤维之间的结合力加强,基体树脂和增韧剂之间发生了相分离,材料的抗冲击性能得到提高。更多还原

【Abstract】 Advanced polymer-based materials have been widely used because of its high strength, high modulus, corrosion-resistant, low density and good dimensional stability. These materials can be used as the structure materials in the aircraft industry due to the low weight reduction of 20-30% as compared to other materials. With the development of high speed aircrafts, harsh atmospheric conditions require high temperature performance-grade materials. Exploration of new type of high temperature performance-grade materials has become a very challenging task.Polyimide is a kind of aromatic heterocyclic polymers with the molecular structure containing imide bonds. It possesses excellent high temperature performance, excellent mechanical properties, thermal dimensional stability and dielectric properties. It is an integrated high performance specialty engineering plastics that can be used for a long time at 250oC. Thermosetting polyimide has attracted considerable attention because of its application at high temperatures. BMI Resins are a class of thermosetting polymers e.g. PMR-15 that are gaining acceptance by industry because they can be used at elevated temperatures 288-316 oC and in wet environments.Thermosetting cross-linked polyimide (PI) prepolymer was synthesized from 4, 4‘-Bisphenol A dianhydride (BPADA) and 3-aminophenylacetylene(APA) through a two-step polycondensation. FT-IR spectrophotometer was used to monitor the hydrogen in acetylene for studying the degree of curing at different temperatures in the curing process. It exhibited low melting temperature before curing, thus a wide processing window and excellent processing performance were expected. After crosslinking it showed good thermal and dimensional stability so that its potential application as resin-based composite materials may be realized in the field of aerospace.However, thermosetting resins after curing became more brittle with lower impact resistance and stress cracking because of higher cross-linking density, which limited its application. Therefore, toughening of thermosetting resins became a subject of interest.There are many ways to toughen thermosetting resins in which the introduction of thermoplastic resin in the thermosetting resins provides the most outstanding comprehensive performance. By controlling the curing conditions, the system can acquire a suitable phase structure such as interpenetrating polymer network (IPN) or phase inversion. This is an effective way to improve the toughness of polymers, which not only increases the toughness of the resin, but also maintains good thermal、chemical and dimensional stability. There are several factors for phase structure: 1. structure and positions of functional groups of the polymers as well as molecular weight: the structure of thermoplastic polymers, the MW and existence of functional groups; 2. curing conditions including temperature, time and solvent selection etc. 3. The compatibility between two kinds of polymers, because compatibility is decisive factor in phase separation and the final phase structure.Therefore, we first selected polyether ether ketone with fluorinated flexible group as a toughening agent to blend with thermosetting resins. The reason for selecting this structure is the low molecular weight and ether moieties in the main chair and fluorinated groups which make the distribution of the molecular chain easy. By studying the processing conditions, we found a suitable solid content of the toughening agents; Blends formed the structure of phase separation or phase inversion by controlling curing conditions. The results of tests showed that the two kinds of polymers are incompatible or partially compatible. SEM studies showed further validates after dissolving toughening parts. Although the thermal stability at high temperatures were affected of some extent, but they still exhibited their high temperature nature. As the concentration of blend films was low, mechanical properties of thin films cannot be tested. We selected three different thermoplastic polyimides as toughening agents, using a diamine and three different anhydrides to study different molecular structures that affect toughening. It was found that the introduction of flexible groups could lead to better properties such as phase separation and phase inversion, thus better toughening effect could be obtained. Molecular symmetry of toughening agents also has effect on results. Research and testing showed that two kinds of polymers are incompatible or partially compatible; they maintained high-temperature thermal stability, the thermal weight loss temperatures of part of the system were increased; Phase separation or phase inversion occurred in blends; The transmittance of films has also been improved at the same time.Using thermoplastic polyimides with side groups of benzene act as a toughening agent to introduce thermosetting polyimide system, we studied the effect of toughening with different solutions. The results showed that solvent have little influence on toughening. The phase separation was easier because of the large space volume and size caused by side group of benzene; thermal stability was not affected and transmittance of films was improved.To further study the toughness effect of carbon fiber reinforced resin material with the thermoplastic toughening agent, we prepared three carbon-fiber reinforced composite materials with resin had been toughness. We had preliminary research about the processing technology and the toughening mechanism, and study the toughening effect and phase morphology. CAI value showed that the toughness effect was improved by 30%; tensile tests also proved that the mechanical properties of composite materials have been improved; in the morphological study it was found that the phase separation between layers of the resin composites; thermal stability retained the same standard. As a conclusion, it has potential research value and applications in the aerospace fields.更多还原