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首页> 外文期刊>Journal of Materials Chemistry, A. Materials for energy and sustainability >Selective cross-linking of oligosilazanes to tailored meltable polysilazanes for the processing of ceramic SiCN fibres
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Selective cross-linking of oligosilazanes to tailored meltable polysilazanes for the processing of ceramic SiCN fibres

机译：寡聚硅氮烷与定制的可熔聚硅氮烷的选择性交联，用于处理陶瓷SiCN纤维

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摘要

An interesting alternative for the processing of non-oxide ceramic fibres at lower costs than that for the current commercially available fibre types was developed by modifying different commercially available liquid oligosilazanes (ML33 and HTT1800) into polysilazanes by selective cross-linking via the N-H and Si-H groups with tetra-n-butylammoniumfluoride (TBAF) as a catalyst. Termination of the reaction with calcium borohydride allows the processing of meltable solid polysilazanes (ML33S and HTTS) with tailored chemical and thermal properties, to fulfil the requirements for the melt spinning of mechanically stable and homogeneous polymeric fibres. The chemical and thermal stability of the polysilazanes ML33S and HTTS were investigated by using GPC, DSC and rheological measurements. These techniques indicate the dependency of the molecular weight and glass temperature on the catalytical cross-linking conditions. Polymers with up to ~10 000 g mol~(-1) show glass-liquid transition (7g) between 65 and 81 °C and viscoelasticity, which are essential properties for the melt-spinning process. The thermal stability of ML33S is ensured up to 220 °C In contrast the thermal stability of HTTS is limited to 170 °C due to the presence of vinyl-groups. The viscoelastic behaviour of the polymer melts, measured by oscillatory rheometry, and the sufficient thermal stability allowed the continuous processing of stable green fibres by melt spinning in the temperature range of 110 to 130 °C After fast electron beam irradiation curing of the green fibres and pyrolysis of continuous amorphous ceramic SiCN fibres from both ML33S and HTTS polysilazanes were successfully synthesized, while a defined T_g point influences the shape and the smoothness positively.
机译：通过经由NH和Si选择性交联将不同的市售液态低聚硅氮烷（ML33和HTT1800）改性为聚硅氮烷，开发了一种以比目前市售纤维类型更低的成本处理非氧化物陶瓷纤维的有趣替代方法。 -H基团以四正丁基氟化铵（TBAF）为催化剂。用硼氢化钙终止反应可以加工具有定制化学和热性能的可熔固体聚硅氮烷（ML33S和HTTS），以满足对机械稳定且均质的聚合物纤维进行熔融纺丝的要求。聚硅氮烷ML33S和HTTS的化学和热稳定性通过GPC，DSC和流变学测量进行了研究。这些技术表明分子量和玻璃温度对催化交联条件的依赖性。最高〜10000 g mol〜（-1）的聚合物在65至81°C之间表现出玻璃-液体转变（7g）和粘弹性，这是熔体纺丝工艺的基本特性。 ML33S的热稳定性可确​​保在高达220°C的温度下。相反，由于存在乙烯基，HTTS的热稳定性被限制在170°C。通过振荡流变法测量的聚合物熔体的粘弹性行为，以及足够的热稳定性，可以通过在110至130°C的温度范围内进行熔体纺丝来连续加工稳定的生坯纤维。成功地合成了由ML33S和HTTS聚硅氮烷合成的连续无定形陶瓷SiCN纤维的热解过程，而定义的T_g点则对形状和光滑度产生积极影响。

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