【作者】 朱宝菊；

【导师】 张军营； 史翎；

【作者基本信息】 北京化工大学 ， 高分子化学与物理， 2009， 硕士

【摘要】 有机硅是一种无机-有机杂化材料,兼具无机材料和有机聚合物的特性,但是在500℃以上的应用环境中很难兼顾良好的耐高温性能与方便的室温固化性能,限制了有机硅材料在航空、航天、大功率集成电路等诸多行业的应用。本实验室合成了一种新型侧活性聚甲氧基硅氧烷树脂(PMOS),可以在室温下通过水解缩合反应形成高交联密度的基体树脂,具有良好的固化及施工工艺性能,但固化物的力学强度较低,不能直接用于耐高温粘接密封场合。因此,研究PMOS基复合材料不仅具有重要的现实应用意义,而且对耐高温高强度有机硅密封材料的研发具有指导意义。本论文使用一系列无机粉体对PMOS树脂进行高温强度与膨胀性能的调节,通过室温水解交联反应制备了PMOS/莫来石等复合材料,采用IR、XRD、SEM等方法研究了复合材料在高温有氧环境下的结构变化,通过TG、DSC等对复合材料的耐热性能进行考察,研究了复合材料的冲击强度、套接压剪强度、抗压强度、膨胀系数随温度的变化规律,并表征了复合材料的介电性能、耐介质性能、导热性能与阻燃性能。研究结果如下:1、莫来石、透锂长石、堇青石、熔融石英粉等材料具有独特的结构与性能特点,可以与PMOS树脂通过复配制备出具有耐高温低膨胀性能的新型复合材料。以有机锡作为催化剂,PMOS/无机粉体复合材料可以在室温下通过水解缩合反应实现交联固化,无机粉体的含量越高,材料的固化时间越短。2、PMOS/莫来石复合材料具有优良的耐高温性能、力学性能、耐介质性能、阻燃性能和介电性能。IR、XRD、SEM表明,随着温度的升高,PMOS/莫来石复合材料中的有机硅基体降解并发生了无机化转变,而莫来石晶体则逐渐生长。PMOS/莫来石复合材料的冲击强度、套接压剪强度、抗压强度等力学性能随老化温度的升高而发生变化,在100～500℃阶段,由于有机硅基体的降解导致复合材料的力学性能逐渐降低,冲击强度由2548J/m~2降为589J/m~2,套接压剪强度由23.08MPa降为11.76MPa,抗压强度由27.3MPa降为15.6MPa;而在500～800℃阶段,莫来石晶体的生长会使复合材料的力学性能有所提高,冲击强度由589J/m~2增大至924 J/m~2,套接压剪强度由11.76MPa增大至19.20MPa、抗压强度由15.6MPa增大至21.7MPa。TG、DSC测试表明,PMOS/莫来石复合材料的耐热性能优于PMOS树脂固化物,500℃时前者残留质量为96%,后者为87%;800℃时前者为93%,后者为82%。莫来石的加入提高了材料的耐热性能。PMOS/莫来石复合材料具有良好的耐介质性能和阻燃性能,在航空煤油中浸泡6个月后,材料的体积无变化,质量保持仍达到99.1%;材料的氧指数≥60,阻燃性能优良。PMOS/莫来石复合材料经过不同温度热处理后高频阶段的介电常数在6.5-9.0之间。3、PMOS/莫来石复合材料在高温环境中尺寸仍然保持稳定,具有较低的热膨胀系数,在100～200℃温度范围内,膨胀系数随着温度的升高而略有增大,且莫来石含量越高时复合材料的膨胀系数越小。更多还原

【Abstract】 Polysiloxanes are semi-inorganic polymers with high thermal stability,good weather resistance,low surface tension,and unusually high permeability.Their degradation above 500℃and the needing of high crosslinking temperature,however,restrict their applications in many areas.Polymethylmethoxysiloxane（PMOS） with dense pendant Si-bound methoxy groups was synthesized in our laboratory,and PMOS could be cured at room temperature with moisture via hydrolytic condensation to form high crosslink density material.While PMOS also had some disadvantages in practical application and the major one lay in their low mechanical strength.In this thesis,a series of PMOS/inorganic powder composites were prepared at room temperature,with good thermal resistance and low expansion.The structure transformation of PMOS/mullite composite at elevated temperatures was characterized using IR,XRD and SEM.The thermal resistant performance was studied by TG and DSC.We also reported investigation of PMOS/mullite composite on impact strength, compress shear strength,compress strength,thermal expansion,dielectric strength,solvent resistance,heat conduction and fire retardant performance.1、Some inorganic powders such as mullite,petalite,cordierite and silica flour could be incorporated with PMOS at room temperature via dibutyltin dilaurate catalyst to prepare materials with good thermal resistance and low expansion.The higher mullite content,the sooner composite cured.2、PMOS/mullite composite could play many good performances.IR XRD and SEM characterized that during the thermal processing PMOS had a degradation reaction while mullite crystallite size grew.As a result, impact strength,compress shear strength and compress strength changed with the temperature.During 100～500℃,impact strength decreased from 2548J/m² to 589J/m²,compress shear strength from 23.08MPa to 11.76MPa and compress strength from 27.3MPa to 15.6MPa.While during 500～800℃,impact strength increased from 589J/m² to 924 J/m², compress shear strength from 11.76MPa to 19.20MPa and compress strength from 15.6MPa to 21.7MPa.Results of TG and DSC showed that the residual mass of PMOS/mullite composite at 800℃was 93.4 wt%, higher than that of crosslinked PMOS.The incorporation of mullite improved thermal resistance of the material.After soak in jet fuel for six months,volume of composite did not change and residual weight was up to 99.1%.Oxygen index of composite was higher than 60%,showing high fire retardant performance.Dielectric constant after thermal degradation was between 6.5 and 9.0.3、PMOS/mullite composite had excellent dimensional stability at elevated temperatures.During 100 to 200℃,coefficient of thermal expansion was at 10-5℃^-1 and decreased with the incorporation of mullite.更多还原