MQ硅树脂改性增强特种炸药用胶粘剂的性能研究

采用共混填充法制备了MQ硅树脂增强的粘结炸药用室温硫化硅橡胶(RTV)胶粘剂,测试结果表明:该胶粘剂粘结炸药时,其剪切强度明显提高,由1MPa左右增加到3.2MPa。同时选用扫描电子显微镜(SEM)来表征MQ硅树脂的分散性,结果显示:填充10%左右MQ硅树脂时,其在RTV胶粘剂中分散均匀,补强效果最好。     

乙烯基MQ硅树脂补强液体硅橡胶的力学性能

液体硅橡胶内聚能密度小、力学强度低,是限制其应用的主要障碍。文中通过正硅酸酯法,合成了一种相对分子质量及乙烯基含量可控的MQ硅树脂,并研究了其对液体硅橡胶的补强作用。研究结果表明,与传统白炭黑补强液体硅橡胶相比,乙烯基MQ硅树脂补强液体硅橡胶的力学性能更优异。当乙烯基MQ硅树脂质量分数达到15%时,液体硅橡胶的拉伸强度达到7.2 MPa,撕裂强度达到44.7 kN/m,断裂伸长率达到453%,Shore A硬度达到53。特别地,乙烯基MQ硅树脂与液体硅橡胶的相容性良好,乙烯基MQ硅树脂补强液体硅橡胶的透光率大于80%,完全符合LED封装对液体硅橡胶力学性能和透光率的要求。     

含亚苯基甲基苯基硅树脂的合成及表征

以甲基、苯基氯硅烷和1,4-二(羟基二甲基硅基)苯为原料,采用水解-缩聚法合成了主链含亚苯基的甲基苯基有机硅树脂,并对其结构和性能进行了研究。红外光谱(FT-IR)和核磁共振(29Si NMR)分析表明,亚苯基被成功引入到硅树脂主链中。差式量热扫描(DSC)分析表明硅树脂为均聚物。热失重(TG)结果表明,在N2氛中,硅树脂在450℃失重约1%,优于普通甲基苯基硅树脂。硅树脂的清漆涂层在300℃下使用时,附着力、抗冲击、柔韧性能仍保持良好。电化学阻抗分析(EIS)结果表明,硅树脂的清漆涂层常温固化后、经300℃的高温烘烤后都具有优良的耐腐蚀性能。     

自由基-阳离子混杂光固化硅树脂的合成与性能研究

通过水解-缩聚法制备了一种可自由基-阳离子混杂光固化的MTQ硅树脂(HUV-MTQ),利用红外光谱、核磁氢谱和凝胶渗透色谱对HUV-MTQ进行了结构表征;采用实时红外对HUV-MTQ光聚合过程中双键和环氧基的转化率进行研究,以此优选出自由基-阳离子混杂光引发剂的最佳配比与用量;并对HUV-MTQ光固化制品的力学性能、光学性能以及热性能随HUV-MTQ缩聚温度的变化进行了分析。结果表明:阳离子与自由基光引发剂的最佳质量比为1.5,最佳质量分数为15.0%,双键和环氧基的最终转化率分别为80.5%和87.4%。在70℃下缩聚制备的HUV-MTQ的UV固化制品的透光率为92.2%,耐热性能与耐黄变性能最好。     

纳米TiO_2对真空紫外辐照下MQ硅树脂增强硅橡胶质损及热性能的影响

采用空间综合辐照模拟设备研究了纳米TiO2对真空紫外辐照下MQ硅树脂增强硅橡胶的质损及热性能的影响。试验结果表明,真空紫外辐照后,硅橡胶会产生质量损失,其质损率随着辐照剂量的增加而增加;真空紫外辐照后硅橡胶的热稳定性随着辐照剂量的增加先增加而后下降;硅橡胶材料的体膨胀/收缩变形变化则随辐照剂量的增加而变化不大。添加纳米TiO2的硅橡胶与未改性硅橡胶相比,经过相同剂量的真空紫外辐照后,质损率增加、耐热性以及体膨胀/收缩率变化的程度均降低,表现出明显的抗辐照性能。     

上海MQ2000高架门机顶升系统改造

上海MQ2000门机经10a高强度的使用,顶升系统元件老化严重,为保障顶升过程的安全可靠,需进行改造。本文分析了原顶升系统存在的问题,确定了机械、电气和液压系统的改造方案,并进行了机电液联调试验和真机拆除试验。试验证明改造方案达到了预期效果,提高了设备的性能。     

硅树脂249的交联与裂解陶瓷化研究

研究了硅树脂249(SR 249)的交联与裂解行为。结果表明,SR 249在250℃能自交联,其机理主要通过硅羟基脱水缩合实现。裂解产物组成为34.69%S i,37.99%C,27.32%O。SR 249的裂解陶瓷化主要在470℃~1150℃范围,分为三个阶段。第一阶段在470℃~600℃区间,裂解活化能为23.32 kJ/m o l,由随机成核步骤控制裂解反应。第二阶段在720℃~800℃区间内,裂解活化能为196.95 kJ/m o l,由三维扩散步骤控制裂解反应。第三阶段在1000℃~1150℃区间内,裂解活化能为135.87 kJ/m o l,由随机成核步骤控制裂解反应。引入纳米级活性填料A l、S i进行裂解,可以减少裂解产物中的自由炭,形成S i-A l-O-C陶瓷。     

低温固化硅树脂的制备及其防腐蚀涂层性能研究

以硅酸乙酯(TEOS)、乙烯基三乙氧基硅烷(VTES)和二甲基二甲氧基硅烷(DMDMS)为硅烷单体,以柠檬酸为催化剂,采用溶胶-凝胶法制备乙烯基甲基硅树脂,并添加固化剂γ-氨丙基三乙氧基硅烷(APTES)使制备的硅树脂可以在较低温度(50℃)下固化。采用红外光谱(FT-IR)对比硅树脂固化前后的结构变化;通过接触角、吸水率、电化学阻抗谱(EIS)测试了不同n(R)/n(Si)、n(Si—OC_nH_(2n+1))/n(H_2O)、pH以及固化剂用量对硅树脂涂层耐水性和防腐蚀性能的影响。结果表明:当n(R)/n(Si)=1.4/1、n(Si—OC_nH_(2n+1))/n(H_2O)=0.2/0.2、pH=2.6、固化剂用量为4%(质量分数)时,涂层具有较好的性能。     

工艺参数对先驱体硅树脂高温连接陶瓷材料的影响

对先驱体硅树脂高温(800～1400℃)转化陶瓷接头连接石墨、陶瓷SiC及Cf/SiC复合材料进行了研究,着重对硅树脂固化裂解过程、硅树脂溶液浓度及裂解温度对连接性能的影响进行了探讨.研究表明,硅树脂的交联固化主要是通过消耗Si-OH来完成,先驱体溶液的浓度及裂解温度根据基材的不同而有不同影响.     

硅树脂基复合材料的制备及耐热性能和弯曲强度

以氯硅烷为原料合成了一种新型的甲基苯基硅树脂,并制备了复合材料。通过热重分析、扫描电镜研究了复合材料的热性能和填料分布,分析了影响复合材料弯曲强度的可能因素。实验结果表明,复合材料的热稳定性优良,在N2气氛下升温至800℃时,热失重仅为4.4%;复合材料截面为连续相,填料在硅树脂中分散均匀,两者相容性较好;填料的添加量、硅树脂的苯基含量及凝胶化时间是材料弯曲强度的三个主要影响因素。     

有机硅改性聚合物的研究进展

从共聚改性、接枝改性和共混改性等几个方面简要介绍了有机硅改性聚合物的研究状况和发展历程.     

Degradation of cement pastes by organic acids

Agriculture produces effluents, like liquid manure and ensilage effluents, that cause serious environmental problems. In order to limit this pollution, manure needs to be stored in water-tight silos often made of concrete. Manure contains organic acids which constitute a severe chemical threat for concrete. This research aims to analyze the degradation mechanisms of cement-based materials stored in organic acids. The results are used to identify the composition parameters of binders that influence durability. Ordinary and blended Portland cement specimens were immersed for 18 weeks in a mixture of 5 organic acids found in liquid manure at a pH of 4. Physical, chemical and mineralogical modifications in the pastes were explored by water intrusion porosity tests, electron microprobe and X-ray diffraction analyses. Analyses were run from the sound to the altered zone. The altered depths and the mass loss variations of the samples were monitored over time. The degradation of the matrix occurs by almost total decalcification, the vanishing of the crystallized or amorphous hydrated phases and the probable formation of a silica gel, which limits the kinetics of further degradation. In the altered zone, the anhydrous silico-calcic grains are chemically modified but C₄AF and slag grains keep their initial composition.     

Barium titanate formation by organic resins formed with mixed citrate

Citric precursors are used to produce BaTiO₃, the Ba/Ti ratio being fixed by a mixed Ba-Ti citrate. The conditions for its solubility in organic agents (ethylene glycol or ethylene glycol+ citric acid) has been studied and used to investigate various routes of synthesis (resin, spray pyrolysis or films). The transformation from the resin to the mineral phase has been investigated. In all cases the powders are aggregates of 150 nm. Their structure is cubic or tetragonal depending upon the route followed and they are at the limit of a structural metastability. Sintering may be accomplished below 1250 °C if the 150 nm aggregates are properly arranged. This depends upon the route chosen to produce them.     

聚醚、氨基改性有机硅乳液的研制

采用乳液聚合合成聚醚、氨基改性有机硅乳液,讨论了乳化剂、催化剂、改性剂用量及反应温度、反应时间对乳液聚合的影响;采用水相和逆相乳化法制得有机硅微乳液,并讨论了乳液的性能。     

Controllable synthesis of silica hollow spheres by vesicle templating of silicone surfactants

Silica hollow spheres (SHSs) have been designed and prepared through three distinct synthetic routes based on the self-assembling of comb-like copolymer silicone surfactants. This process was based on the rule of similarities for hydrophobicity and hydrophilicity between the surfactant and a silica source. The directed silica wall formations were performed at different confined spaces of the vesicles, including the outer and inner surfaces, and the hydrophobic parts of the bi-layers. The resultant SHSs possess tailorable shell thicknesses (20–400 nm), particle sizes (200 nm–1.2 μm), and a high dispersibility in aqueous solutions.     

Well-defined coordination environment breaks the bottleneck of organic synthesis:Single-atom palladium catalyzed hydrosilylation of internal alkynes

Single-atom site(SAS)catalysts have attracted considerable attention due to their excellent performance.However,most of the current research models of SAS catalysts are based on inorganic catalysts,where“metal and coordination atom interaction”cannot simulate the fine-tuning effect of organic ligands on metal catalytic centers in homogeneous catalysts.Therefore,certain chemical transformations in homogeneous catalysis cannot be perfectly replicated.Here,we used porous organic ligand polymers as the carrier,which effectively changes the charge regulation of nanoparticles and monoatomic metal catalysts.Drawing lessons from traditional homogeneous metal/ligand catalysis,we introduced various functional groups into the ligand polymers to adjust the electronic properties,and successfully realized the hydrosilylation of internal alkynes with high catalytic performance.The selectivity and catalytic efficiency under the Pd@POL-1 catalyst system were improved compared with previous studies.The internal alkynes with various structures can complete this reaction,and the ratio of E/Zcan reach up to 100:1.     

酶法合成脂肪族聚酯的研究进展

酶法合成的脂肪族聚酯不仅是具有生物可降解性的高聚物,而且具有良好的生物吸收性,保证了其作为医用材料的安全性.酶法合成脂肪族聚酯的方法是一种新型的环境友好绿色化学技术,合成条件温和,产物易于分离,可以弥补传统合成方法的不足.本文评价了酶法合成脂肪族聚酯的发展现状和最新研究进展,介绍了酶催化合成脂肪族聚酯的方法及影响因素.     

微波辅助酸化蒙脱土催化合成乳酸正丁酯的研究

采用微波辐照法对钠基蒙脱土进行了酸化改性,制备出了酸化蒙脱土(H-MMT)固体酸催化剂,并利用X射线衍射、低温物理吸附等技术对催化剂性质进行了表征,结果表明,经微波辐照酸改性的催化剂层状结构没有被破坏,层间距略有下降,结晶度降低;比表面积和孔径都增大,形成了较好的介孔结构;表面酸量增加.这些特性使得催化剂表现出良好的催化活性.而后,以H-MMT为催化剂,系统研究了乳酸正丁酯的微波辅助合成方法,考查了催化剂用量、微波功率以及微波辐照时间对酯化率的影响.结果表明,微波功率200W、辐照15min、催化剂用量6.0%(占乳酸和正丁醇总质量)为最优的酯化条件,在此条件下,酯化率可达72.4%.最后,探讨了微波辅助H-MMT催化合成乳酸正丁酯的机制,发现H-MMT与微波具有协同作用.微波辅助H-MMT催化合成乳酸正丁酯是一种高效、节能、环境友好的方法,具有市场推广前景.     

一种聚苯基甲基硅氧烷改性环氧树脂耐高温防腐蚀涂料的制备研究

采用苯基三甲氧基硅烷和苯基甲基二甲氧基硅烷水解合成了聚苯基甲基硅氧烷(PS),然后改性E-20环氧树脂,通过环氧值、红外光谱分析表明,有机硅接枝了环氧树脂且环氧基保持不变。用DSC、TGA分析了有机硅含量对改性树脂固化体系耐热性能的影响,当m(E-20)∶m(PS)=100∶25时,化学改性树脂固化体系的耐热性能明显提高。以此改性树脂为基料,采用适宜的固化剂,添加适当的颜料、功能填料、助剂等制备耐高温防腐蚀涂料。结果表明,该涂料不仅具有优异的常规涂膜性能,同时还具有优异的耐高温及防腐蚀性能。