Effect of curing and pyrolysis processing on the ceramic yield of a highly branched polycarbosilane

In this article, the influence of curing processing on the final ceramic yield of a highly branched polycarbosilane is discussed. Effect of pyrolysis conditions on the ceramic residue is also investigated. The results show that post-treatment can highly increase the crosslinking degree and pyrolysis yield, but has little influence on the final ceramic yield. The heating rate between 170 and 200 °C shows a little effect on the ceramic residue. Adding the catalyst into polymer, pyrolysizing with the gas pressure and improving the heating rate during the pyrolysis process can efficiently increase the final ceramic yield.     

Mechanism of cyclohexene vapor curing polycarbosilane fibers

Cyclohexene vapor, instead of air, is applied to cure polycarbosilane (PCS) fibers. The cured fibers are characterized by infrared (IR), electron spin resonance (ESR), elements analysis (EA) and simulated through the HyperChem^TM program for comparison. The curing process is investigated by thermoanalysis. The results indicate that the Si–H and Si–CH₃ bonds in PCS are induced by cyclohexene to cleavage and form Si-central radicals. A fully developed cross-linking fibers come into being through the combination of these radicals, and the byproducts, some cyclohexyls bonded onto PCS derived from cyclohexene, introduce the variations in IR spectra, weight gain and carbon contents increase of PCS. On the basis of investigation and simulation, a likely mechanism of curing reaction is presented.     

聚碳硅烷纤维在环己烯气氛中的不熔化处理

将聚碳硅烷(PCS)纤维在环己烯气氛中进行化学气相交联不熔化处理,其氧含量比空气不熔化处理大大降低,组成和结构也发生了变化,气体副产物中存在环己烷和小分子硅烷.在环己烯气氛中,随着温度的升高,PCS分子的Si-H键的反应程度逐渐提高,纤维的凝胶含量逐渐增大.环己烯受热引发PCS分子中的Si-H和Si-CH3键断裂生成Si自由基和Si-CH2自由基,促进PCS分子间形成Si-CH2-Si交联结构;同时,环己烷作为侧基引入到PCS分子结构中,使纤维的碳含量随之增高.随着反应温度的升高,部分环己烷侧基和少量小分子硅烷会从PCS分子主链脱出.     

Development of a resin curing model for UV nanoimprint

UV nanoimprint lithography uses UV light as an energy source. It is performed at room temperature and low pressure, and has its own merits as compared to thermal nanoimprint. In this paper, a measurement system was developed to measure the degree of resin curing in UV nanoimprint to improve our understanding of the resin solidification phenomenon. A curing model was then established based on the measurement results. The measurement system measured the degree of cure in real time and was composed of a Fourier transform infrared spectroscopy system, a UV light source, and an optical guide. Also, new UV-curable resins that had low viscosity values were developed for the UV nanoimprint process, and imprint tests using these resins were performed successfully. The curing model considered the UV irradiation time, power, and curing temperature, which are important parameters in the UV nanoimprint process. The degree of cure had an exponential relation to UV irradiation time, power, and temperature; thus, the curing model was expressed as an exponential function of the UV irradiation time, power, and temperature. The developed model was verified for various UV-curable resins.     

碳纳米管/环氧丙烯酸酯紫外光固化涂层的制备及光阻隔性能

利用碳纳米管(CNTs)表面官能团与环氧丙烯酸酯(EA)齐聚物的反应, 制备了碳纳米管/环氧丙烯酸酯(CNTs/EA)光敏性树脂, 通过紫外光(UV)固化交联制备出新型复合涂层。研究了涂层的阻隔红外/紫外线性能, 在近红外区(4000~12000 cm-1)的阻隔率为68.55%, 对可见光(380~780 nm)的透过率大于85％, 对于＜300 nm的紫外线完全阻隔。同时复合涂层力学性能与EA涂层相比也得到提高, 在光阻隔涂层方面具有潜在的应用前景。      

光固化硅橡胶胶粘剂的研制

采用聚氨酯丙烯酸酯制备了光固化胶粘剂并对硅橡胶进行了粘接,讨论了光引发剂和活性稀释剂含量对胶粘剂性能的影响,利用红外光谱仪和扫描电镜对胶粘剂进行表征,得到了一种具有优良光固化性能和剪切强度的光固化硅橡胶胶粘剂.     

新型紫外光固化涂料的研究进展

介绍了紫外(UV)光固化涂料的组成(包括光引发剂、活性单体、齐聚物、助剂)及其作用.在此基础上,对几种新型UV固化涂料,如UV固化水性涂料、UV固化粉末涂料、UV固化纳米涂料和UV固化超支化聚合物涂料等的特点及国内外研究进展进行了综述,并指出UV固化涂料的发展方向.     

A study of the oxidation curing mechanism of polycarbosilane fibre by solid-state high-resolution nuclear magnetic resonance

The chemical structure of oxidation-cured polycarbosilane fibres has been studied by IR and chemical analysis, but its structure has not been identified in detail. In this work, the molecular structure was examined by chemical analysis, and solid state¹³C and²⁹Si nuclear magnetic resonance (NMR) spectroscopy. Si-O-Si, Si-O-C(I) and Si-O-C(II) bonds were formed by the oxidation curing process. The six chemical bonds (Si-C, Si-H, Si-Si, Si-O-Si, Si-O-C(I) and Si-O-C(II)) in oxidation-cured polycarbosilane were determined quantitatively, and the chemical structural model was shown. Solid state²⁹Si resolution NMR spectroscopy has proved to be a powerful tool for investigating the curing mechanism of oxidation-cured polycarbosilane fibres.     

高支化碱溶性聚酯的合成及光成像研究

通过1，2，4-苯三甲酸酐和环氧氯丙烷合成高支化碱溶性聚酯，再用丙烯酸与多官能团环氧树脂反应产物对高支化聚酯改性得到高支化碱溶性感光聚合物；研究了这类聚合物的碱溶性、感光性和光成像特性。探索了光致抗蚀剂的配方组成和成像因素。结果表明，以接枝引入15%改性多官能团环氧树酯配制的光致抗蚀剂综合性能最好，分辨率3um以内（白光）。     

UV固化防雾功能预聚物的制备与性能研究

以间苯二甲酸-5-磺酸钠、二缩三乙二醇和甲基丙烯酸为原料,以对甲苯磺酸为催化剂,四甲氧基酚为阻聚剂,二甲苯为带水剂,经缩聚、酯化合成了UV固化防雾功能预聚物;采用红外光谱仪(IR)、紫外-可见分光光度计、凝胶渗透色谱(GPC)、光学接触角测量仪(OCA)和热重分析仪(TG-DSC)对其性能进行了表征与分析;通过设计正交试验探究其UV固化成膜的较为理想的工艺配方.结果表明:实验制备的预聚物适合于制备UV固化防雾涂料,制备所得防雾涂膜耐水、防雾,具有较好的硬度、附着力及热稳定性.     

Conversion of polycarbosilane (PCS) to SiC-based ceramic Part 1. Characterisation of PCS and curing products

A commercial polycarbosilane (PCS) preceramic polymer has been characterised as-received and following curing under a variety of conditions. Elemental analysis, gel permeation chromatography (GPC), infra-red spectroscopy (FT-IR), simultaneous thermogravimetric analysis-differential thermal analysis (TG-DTA) and solid state nuclear magnetic resonance (NMR) have been employed. A number average molar mass of 1200 was found with a broad molar mass distribution ( / = 2.97). Elemental analysis gave an empirical formula of SiC_2.2H_5.3O_0.3. IR and Solid state ²⁹Si and ¹³C NMR spectra showed the presence of Si-O-Si, SiC₄, SiC₃H, Si-Si, Si-CH₃ and Si-CH₂ groups. Simultaneous TG-DTA performed under an argon flow showed that there was a weight gain which started at approximately 240 °C. DTA showed an exotherm starting at this temperature showing that there was oxidation of the polymer even in an inert atmosphere. This is perhaps due to the oxygen in the PCS and there may also be some impurities in the inert atmosphere. Evidently the PCS is very sensitive to oxygen. Above 500 °C, weight loss dominated although the exotherm continued to approximately 700 °C. The effect of heating rate and dwell time at 200 °C on the changes in the chemical composition during curing have been explored using IR and solid state NMR spectroscopies, and elemental analysis. The longer the cure time the higher was the weight gain and greater was the extent of the oxidation reactions. Elemental analysis showed that the ratio of H and C to Si decreased with holding time at the cure-temperature while the amount of oxygen increased. Use of a higher heating rate resulted in a lower weight gain when the same holding time was used. From this it is clear that curing starts below the holding temperature.     

高度支化聚合物在原油破乳中的应用

介绍了影响原油破乳剂性能的一些参数,包括最佳烷烃指数、动态界面张力梯度、界面膜强度等.评述了超支化聚合物和树枝状聚合物作为新型破乳剂的可能性和存在问题.     

不同紫外光固化涂料的涂膜性能研究

通过不同齐聚物、单体稀释剂、引发剂、促进剂的组合得到不同的紫外光(UV)固化涂料,研究了UV涂料的附着性、光泽、柔韧性、耐溶剂性,以及在不同材质表面的涂膜性能。通过实验可以看出:环氧丙烯酸酯齐聚物具有良好的附着力、颜料润湿性、高光泽、高硬度与优异的耐溶解性;聚氨酯丙烯酸酯齐聚物具有反应活性高、固化速度快、优异的耐黄变性能、优异的附着力、柔韧性、抗化学品性和耐磨性;聚酯丙烯酸酯齐聚物具有良好的光泽、耐候性能、固化性能和保光性能较好。将以上三者按不同比例搭配使用,配合相应的组成成分,可灵活地设计出具有实用价值的紫外光固化涂料产品。