【作者】 张承双；

【导师】 陈平；

【作者基本信息】 大连理工大学 ， 材料学， 2009， 博士

【摘要】 聚对苯撑苯并二噁唑(PBO)纤维增强含二氮杂萘酮联苯结构的聚芳醚砜酮(PPESK)树脂基复合材料(PBO/PPESK)具有优异的力学性能和耐热性能,同时还具有较好的吸波隐身功能,预期可作为火箭、导弹、无人机等的外层结构材料和内部承力机构材料,在航空航天和国防军工等领域具有很好的推广应用前景。但是,PBO/PPESK复合材料存在界面粘结性能差的问题。界面是复合材料的“心脏”,是连接增强体与树脂基体的纽带和桥梁,对复合材料的性能起到至关重要的作用,界面粘结性能的好坏直接影响复合材料的力学性能、耐热性能甚至复合材料的使用寿命,良好的界面粘结是提高复合材料质量的关键。PBO纤维由于分子链结晶取向度高,表面光滑,表面化学活性低,缺少极性基团,使得其与树脂基体很难形成良好的浸润和有效的化学键合,导致PBO/PPESK复合材料的界面结合强度较低。基于此,有必要对PBO纤维进行表面改性,以提高PBO纤维的浸润性能及其与PPESK树脂基体间的界面粘接性能,进而有效地提高PBO/PPESK复合材料的综合性能。本文利用射频感性耦合氧气等离子体对PBO纤维进行了表面处理,分别采用X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、原子力显微镜(AFM)及动态接触角分析(DCA)系统研究了氧气等离子体处理时间、放电气压、放电功率等工艺参数对PBO纤维的表面化学成分、表面形貌、表面粗糙度及表面自由能的影响。研究结果表明:氧气等离子体处理能够在PBO纤维表面引入O-C=O基等极性基团,使纤维表面极性基团的含量增加,等离子体对纤维表面具有明显的刻蚀作用,经等离子体处理后PBO纤维的表面粗糙度增加,表面自由能增大,纤维的浸润性能得到明显改善。利用氧气等离子体对PBO纤维进行表面处理时应选择合适的等离子体处理工艺参数。利用溶液预浸湿法缠绕成型和高温模压工艺制备连续PBO纤维增强PPESK树脂基复合材料,并采用氧气等离子体对PBO/PPESK复合材料进行了界面改性研究。通过层间剪切强度(ILSS)及吸水率测试表征了氧气等离子体处理时间、放电气压、放电功率等工艺参数对PBO/PPESK复合材料界面粘结性能的影响,采用SEM对复合材料的断面形貌进行了分析。研究结果表明:氧气等离子体处理能够使PBO/PPESK复合材料的ILSS增大,吸水率降低,复合材料的界面粘结性能得到明显改善。在载荷的作用下,PBO/PPESK复合材料的破坏模式由未处理的界面脱粘破坏转变为氧气等离子体处理后树脂基体的破坏。利用氧气等离子体对PBO/PPESK复合材料进行界面改性时应该选择适宜的等离子体处理条件,等离子体处理时间过长、放电气压偏低、放电功率过大都可能对PBO纤维的本体性能造成损伤,导致PBO/PPESK复合材料界面粘结性能下降。氧气等离子体处理能够提高PBO/PPESK复合材料的界面粘结性能主要是基于PBO纤维与PPESK树脂基体间的化学键合作用和机械嵌合作用的协同效应,纤维与树脂基体间的化学键合作用对复合材料界面粘结性能的贡献大于机械嵌合作用。当氧气等离子体处理时间为15min、放电气压为30Pa、放电功率为200W时,PBO/PPESK复合材料的界面粘结性能最好。采用DCA、XPS及AFM对氧气等离子体处理的时效性进行了研究,结果表明:经氧气等离子体处理后的PBO纤维在空气中放置一段时间后,纤维表面的活性粒子与活性基团之间发生了一系列的重排或者后反应,反应的结果是PBO纤维表面自由能降低,表面极性基团的含量减少,纤维表面粗糙度先增大后减小。ILSS及吸水率测试表明氧气等离子体处理的时效性会使PBO/PPESK复合材料的界面粘结性能下降。PBO纤维表面及PBO/PPESK复合材料界面的时效行为发生在PBO纤维经等离子体处理后的头几天内,随着时效时间延长,纤维表面及复合材料的界面状态逐渐趋于稳定,时效行为不再显著。进一步利用氧气等离子体接枝环氧树脂对PBO/PPESK复合材料进行了界面改性研究。通过正交试验确定了氧气等离子体接枝环氧树脂改性的最佳工艺条件为:氧气等离子体放电功率为50W、处理时间为10min、放电气压为30Pa、接枝剂(环氧树脂/丙酮接枝液)浓度为3%。ILSS、吸水率、SEM及热失重(TGA)研究结果表明:氧气等离子体接枝环氧树脂改性能够在显著提高PBO/PPESK复合材料界面粘结性能的同时使复合材料保持优异的耐热性能,接枝改性后的复合材料不容易发生剪切破坏。FT-IR及DCA结果显示,环氧树脂在PBO纤维表面发生了接枝聚合反应,环氧基团的接枝反应程度达到60.8%,氧气等离子体接枝环氧树脂改性能够使PBO纤维的表面自由能增加,纤维的浸润性能得到改善。更多还原

【Abstract】 Due to the exceptionally high specific strength and modulus, excellent thermal and oxidative stability, good wave-absorbing and stealthy performance, poly(p-phenylene benzobisoxazole) (PBO) fiber reinforced poly(phthalazinone ether sulfone ketone) (PPESK) composites provide great potential applications as outer-structural and inner-carrier materials in aeronautical and astronautical applications, national defense and military applications. However, the interfacial adhesion of PBO/PPESK composite is poor. Interface is the key structure of composites, it plays important roles in linking reinforcements and the matrix, which influences the mechanical properties, heat-resistance and even life-spans of the composites significantly. Good fiber-matrix interfacial adhesion results in high quality of the composites. The interfacial adhesion of PBO fiber reinforced composites is poor because of the relatively smooth and chemically inactive fiber surfaces which prevent efficient chemical and physical bonding in the interface. Therefore, surface modification of PBO fibers is of great importance in the field of composites application.PBO fibers were surface-modified by inductively coupled oxygen plasma treatment in this paper. The effects of oxygen plasma treatment time, discharge pressure and plasma power on surface chemical composition, surface morphologies, surface roughness and surface free energy of PBO fibers were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic contact angle analysis (DCA), respectively. The results indicated the oxygen plasma treatment introduced some polar groups (such as O-C=O) to PBO fiber surfaces, enhanced surface roughness and changed surface morphologies of PBO fibers by plasma etching and oxidative reactions. Surface wettability of PBO fibers was significantly improved by increasing surface free energy of the fibers via oxygen plasma treatment. Plasma treatment conditions should be appropriate during surface modification of PBO fibers by oxygen plasma.The effects of oxygen plasma treatment time, discharge pressure and plasma power on interfacial adhesion of PBO/PPESK composite were characterized by interlaminar shear strength (ILSS) and water absorption measurements. Fractured surface morphologies of the composites were still observed by SEM. The results showed that the ILSS of PBO/PPESK composite increased while the water absorption degraded after oxygen plasma treatment, the interfacial adhesion of the composite was significantly improved consequently. The primary failure mode of PBO/PPESK composite shifted from interface failure to matrix fracture after oxygen plasma treatment. Plasma treatment conditions should be appropriate during interface modification of PBO/PPESK composite by oxygen plasma treatment. Too long plasma treatment time, too low discharge pressure and too high plasma power would damage the inherent-performance of PBO fibers, which then led to the degradation of interfacial adhesion of PBO/PPESK composite. The interfacial adhesion of PBO/PPESK composite was improved by oxygen plasma treatment due to the chemical linkage and mechanical bonding between PBO fibers and PPESK matrices, and the chemical linkage effect do more contribution than the mechanical bonding on improving the interfacial adhesion of PBO/PPESK composite. The interfacial adhesion of PBO/PPESK composites reached to plateau when the plasma treatment time is 15min, the discharge pressure is 30Pa and the plasma power is 200W.Aging behaviors of oxygen plasma treatment were investigated by DCA, XPS and AFM analysis. The results suggested that when the oxygen-plasma-treated PBO fibers were exposed in air for some days, the active particles and polar groups in fiber surfaces would took some reorientation and post-reactions, which results in a degradation of surface free energy of PBO fibers and a reduction of polar groups in the fiber surfaces. Surface roughness of the fibers increased firstly and then decreased. The ILSS and water absorption measurements indicated that the interfacial adhesion of PBO/PPESK composite degraded because of the aging behaviors of oxygen plasma treatment. Aging behaviors of PBO fibers and PBO/PPESK composites appeared in the first several days after oxygen plasma treatment, minor aging effects were observed with the duration of the aging time because the surface and interface states became stable with aging time increasing.Oxygen-plasma-grafting-epoxy treatment was further used modifying the interfacial adhesion of PBO/PPESK composites. Optimal treatment condition was obtained by orthogonal experiments, which can be stated as: the plasma power is 50W, the plasma treatment time is 10min, the discharge pressure is 30Pa and the concentration of grafting solution (Epoxy/Acetone solution) is 3%. The ILSS, water absorption, SEM and thermogravimetry analysis (TGA) results showed that the oxygen-plasma-grafting-epoxy treatment improved the interfacial adhesion of PBO/PPESK composites significantly but without influencing heat-resistance properties of the composites. The composites were hard to destroy by interface shear load after interface modification. FT-IR and DCA analysis indicated the epoxy groups polymerized in PBO fiber surfaces, and the reaction extent reached to 60.8%. Surface free energy of PBO fibers increased after the treatment, surface wettability of the fibers was improved consequently.更多还原