【作者】 卓东贤；

【导师】 梁国正；

【作者基本信息】 苏州大学 ， 材料学， 2011， 博士

【摘要】 高性能热固性树脂(High Performance Thermosetting Resin, HPTRs)是一类具有网状结构的交联高分子材料,它独特的结构赋予其优异的综合性能,表现出突出的耐热性和热氧化稳定性、优良的综合力学性能及良好的耐湿热、耐辐射及耐腐蚀等特点,因而在航空航天、电子信息、电气绝缘等尖端工业领域占据不可或缺的重要地位。然而,与一般热固性树脂一样,它们同样存在固化物阻燃性差的缺点,对于许多尖端领域的应用场合来说,易燃性已经成为制约HPTR应用的“瓶颈”,所以对它们进行阻燃改性是近年来HPTR研究领域的重点。然而,现有改性方法虽然有效地增加了HPTR的阻燃性能,但往往会牺牲它们原有的一些优异性能,不能满足飞速发展的现代工业对HPTR的更多更高的性能要求。因此,如何在保持HPTR原有突出性能的基础上,实现HPTR的阻燃改性是当今高分子材料领域的重要研究课题,它兼具重要的科学意义和巨大的应用前景。本文即是围绕这个主题而展开。首先,我们制备了具有高长径比的中空管状SiO2(HST),以其作为无机硅系阻燃剂应用到氰酸酯(CE)树脂中,探讨了HST对CE树脂固化反应性及固化物综合性能的影响。研究结果表明,复合材料的性能与HST的含量密切相关,究其本质是因为HST的含量对复合材料的化学结构和聚集态结构产生显著影响。与CE树脂相比,具有合适HST含量的HST/CE复合材料的力学、阻燃、耐吸湿、介电以及耐热等性能显著提高。其次,从分子结构设计的角度出发,通过苯基三甲氧基硅烷的受控水解,合成了一种含大量苯基与硅羟基的新型超支化苯基硅树脂(HBPSi),将其应用于CE树脂、双马来酰亚胺-三嗪(BCE)树脂和环氧(EP)树脂的改性。研究结果表明,大量柔性的线性硅氧链节与刚性苯环、大的自由空腔、苯环间π-π共轭作用及低的交联密度使改性热固性树脂能够在基本保持或提高树脂原有的突出性能的基础上,同时赋予三种热固性树脂优异的韧性、强度与刚性,尤其以HBPSi/EP体系力学性能的改善效果最为明显。此外,HBPSi还能够显著地提高热固性树脂的阻燃性能,表现为改性树脂的热释放速率(HRR)大幅度地降低,且LOI值显著地提高。究其原因,是因为燃烧过程中热固性树脂的裂解产物不仅能够攻击有机硅树脂结构中的Si-C形成交联结构,而且能够与HBPSi中的硅羟基反应,进而起到成炭剂的作用,从而在树脂表面形成一层炭层,最终通过屏蔽作用有效地提高了树脂的阻燃性能。第三,针对CE与烯丙基双酚A改性双马来酰亚胺(BDM/DBA)树脂的结构特点,设计并合成了分别带有硅羟基与-NH2基的两种新型梯形聚苯基倍半硅氧烷(PLS与N-PLS)。在此基础上,设计并制备了PLS/CE和N-PLS/BDM/DBA杂化树脂。研究结果表明,两种杂化树脂的阻燃性能均明显优于原树脂。就BDM/DBA树脂而言,10 wt% N-PLS的加入使树脂的LOI值由26.1 %增大到41.3 %,而其峰值热释放速率(PHRR)与总热释放量(THR)只有BDM/DBA树脂相应值的68 %和58 %。此外,与原树脂相比,两种杂化树脂具有突出的热尺寸稳定性。当N-PLS的含量为15 wt%时,N-PLS/BDM/DBA杂化树脂在玻璃态和橡胶态下的线性热膨胀系数(CTE)分别仅为BDM/DBA树脂的51 %和58 %。杂化树脂所具有的优异性能可归结为PLS和N-PLS自身优异的耐热与阻燃性能,以及其与原树脂的良好反应性。第四,通过不同水解速率的硅烷偶联剂(苯基三甲氧基硅烷与γ-氨丙基三乙氧基硅烷)的受控水解(A2B3C3D)合成了一系列完全封端、含苯基与-NH2基摩尔比率及支化度可控的新型超支化聚倍半硅氧烷(Am-HPab,a和b为苯基三甲氧基硅烷和γ-氨丙基三乙氧基硅烷的摩尔比率),并设计制备了改性CE和BDM/DBA树脂体系。研究结果表明,热固性树脂的性质、Am-HPab的结构与含量均对改性树脂的性能有显著影响。通过调节a和b的比率实现对Am-HPab结构的控制,从而可以获得具有不同性能特色的改性树脂。其中,Am-HP82能够在保持BDM/DBA树脂原有刚性的基础上,全面提高BDM/DBA树脂的综合性能(包括介电性能、韧性、耐吸湿及阻燃性能)。当Am-HP82的含量为10 wt%时,改性树脂的PHRR和THR分别仅为BDM/DBA树脂的20 %和17 %,显示出优异的阻燃性能。阻燃性能的提高主要归因于Am-HPab达到了多效协同阻燃机制的效果,即成功融合了产生气源、凝聚相阻燃机制、屏蔽作用及提高耐热性能等四种阻燃效应。最后,针对现有有机硅树脂存在的固化工艺性和韧性差等不足,通过γ-环氧丙氧基丙基三甲氧基硅烷的受控水解(A2B3C)合成一种完全封端且含大量环氧基的新型超支化聚倍半硅氧烷(B-HBPSi),将其应用于有机硅树脂(SLER)的改性。研究结果表明,B-HBPSi/SLER体系不仅具有较高的固化反应活性和优良的成型工艺性,而且所有B-HBPSi/SLER树脂的介电性能、冲击强度、耐湿热性及高温下的残炭率(Yc)均明显优于一般热固性树脂的相应值。B-HBPSi/SLER树脂的突出综合性能使之在电子封装材料、先进复合材料树脂基体、高性能胶黏剂及绝缘漆等领域具有广阔的应用前景。更多还原

【Abstract】 High performance thermosetting resins (HPTRs) are a class of polymers with cross-linked network structure, and has received great attentions owing to their outstanding integrated properties including high mechanical properties, outstanding thermal, thermal-oxidative and hot-wet resistance, excellent dielectric properties as well as corrosion and radiation resistance, showing great potential in many cutting-edge fields, especially aerospace, electric and electronic industries. However, being polymers, HPTRs generally have poor flammability which is also one major disadvantage to restrict further prosperity of HPTRs for applications in cutting-edge fields. In fact, improving flame retardancy has been the main subject associated with the investigations of HPTRs for many years. To date, many approaches have been developed to effectively improve the flame retardancy of HPTRs, however they tend to sacrifice the original outstanding properties of HPTRs, and thus can not meet the harsh requirements on HPTRs proposed by the rapid development of modern industries. Therefore, developing new flame retardants for HPTRs, which can not only significantly improve the flame retardancy, but also simultaneously endow modified resins with other key properties is an interesting subject to be addressed, this is the subject of this thesis.First, hollow silica tubes (HSTs) with uniform size and high aspect ratio were prepared by hydrolyzing tetraethyl orthosilicate using template self-assembly from D, L-tartaric acid. The effect of the incorporation of HST to the cyanate ester (CE) resin on the curing behavior and integrated properties were systematically evaluated. Results disclose that properties of HST/CE composites are dependant on the content of HST. Essentially, the content of HST has significant influence on the structure of polymer chain and that of aggregation state for the crosslinked networks. Compared with CE resin, the composites with suitable content of HST have not only obviously catalyzed curing reactivity, but also significantly improved integrated properties including mechanical, thermal and dielectric properties as well as water absorption and flame retardancy.Second, based on the molecular design, a novel hyperbranched phenyl silicone resin (HBPSi) containing a large amount of phenyl and silanol groups derived from the hydrolysis of phenyltrimethoxysilane was designed and synthesized, which is then employed to modify CE, bismaleimide-cyanate (BCE), and epoxy (EP) resins. It is found that modified thermosetting resins with suitable contents of HBPSi have effectively improved toughness, strength and stiffness, especially for the modified EP system. These attractive results can be attributed to the synergistic effect resulting from changes of both polymer chain and aggregation state structures including a large amount of flexible linear siloxane segments, rigid benzene rings, many unoccupied spaces,π-πconjugation interaction among benzene rings, and low cross-linking density. In addition, HBPSi modified thermosetting resins have significantly improved flame retardancy, showing decreased heat release rate (HRR), and improved limited oxygen index (LOI). Investigations on thermal-oxidative stability and residual char demonstrate that HBPSi can induce cross-linking reactions, and promote to form a char on the surface of the modified resin during combustion. The char acts as a good insulating barrier, which not only prevents the mass transport, but also protects the underlying polymer from flaming, ultimately improving the flame retardancy of the thermosetting resin.Third, according to the structural features of CE and 4,4’-bismaleimidodi-phenyl methane/2,2’-diallyl bisphenol A (BDM/DBA) resin, a novel organically functionalized ladderlike polyphenylsilsesquioxane with Si-OH groups (coded as PLS), and that with–NH2 groups (coded as N-PLS) were synthesized, and then used to develop new high performance hybrids based on CE or BDM/DBA resin. Compared with neat thermosetting resin, the hybrids show significantly improved flame retardancy. In the case of N-PLS10/BDM/DBA hybrid (with 10wt% N-PLS), its LOI increases from about 26.1 to 42.1 %, while its peak heat release rate (PHRR) and total heat release (THR) are only about 68 % and 58 % of that of BDM/DBA resin, respectively. In addition, all hybrids have outstanding dimensional stability. Specifically, its coefficient of thermal expansion (CTE) in glassy state and rubbery state of N-PLS10/BDM/DBA hybrid are only about 51 % and 58 % of that of BDM/DBA resin, respectively. These attractive improved properties are attributed to the outstanding thermal stability and flame retardancy of PLS and N-PLS, and their good dispersion with resin.Subsequently, a novel fully end-capped hyperbranched polysiloxane (Am-HPab, a and b represent the molar ratio of phenyltrimethoxysilane andγ-aminopropyl triethoxysilane, respectively) with controlled branching degree and amine-groups was successfully synthesized by a controlled hydrolysis of phenyltrimethoxysilane andγ-aminopropyl triethoxysilane, and then used to develop new modified CE and BDM/DBA resins. Results show that the nature of thermosetting resin as well as the structure and content of Am-HPab have significant influences on the integrated properties of modified resins. Through controlling the molar ratio of a and b, we can prepare modified resin with different characteristics of performance. It is found that Am-HP82 can successfully endow BDM/DBA resin with improved overall properties (including flame retardancy, mechanical, dielectric and thermal properties, etc.). Specifically, the cone calorimeter measurements clearly indicate that the average heat release rate (AHRR) and THR of modified BDM/DBA resin with 10 wt% Am-HP82 are only 20 % and 17 % of that of neat BDM/DBA resin, respectively, exhibiting outstanding flame retardancy. A synergistic flame retarding mechanism is believed to be attributed to these results, which includes improved thermal stability, producing non-combustible gas, acting in the condensed phase, and providing a barrier for heat and mass transfer owing to the introduction of Am-HPab to BDM/DBA.Finally, in order to overcome the poor curing processing and toughness of silicone resin, a reactive hyperbranched polysiloxane (B-HBPSi) with a large amount of epoxy groups was designed and synthesized through the hydrolyzation ofγ-aminopropyl triethoxysilane, and hexamethyldisiloxane, and then used to prepare a new silicone resin system with a commercial silicone resin (SLER). Results show that cured B-HBPSi/SLER resin possesses outstanding dielectric properties, toughness, water resistance, and high char yield at high temperature, these properties are better than most thermosetting resins, exhibiting great potential to be used as high performance electronic packaging materials, resin matrices of advanced composites, adhesives, and insulating varnish, etc.更多还原