不同Al含量聚铝碳硅烷纤维空气不熔化及氧含量控制研究

Studies on the Air Curing and Oxygen Control of Polyaluminocarbosilane Fibers with Different Al Contents

利用低分子量聚碳硅烷(L-PCS)与乙酰丙酮铝间的热聚合反应,通过调节原料配比和反应条件,合成了不同Al含量,且具有良好可纺性的聚铝碳硅烷(PACS).研究了PACS的分子量分布和分子结构,PACS纤维空气不熔化特点并与PCS纤维进行比较.结果表明,[Al(Ac Ac)3]以-Al(Ac Ac)2悬挂和-Al(Ac Ac)-桥联两种方式接入L-PCS分子结构,PACS分子量呈双峰分布.PACS中Si—H含量和反应活性随Al含量增加而下降,氧化生成的Si—OH难以进一步形成Si—O—Si交联结构.这导致Al含量越高,凝胶点温度越高,凝胶含量随温度升高增加缓慢,同时引入多余氧.通过预氧化与高温处理相结合的方法,将不熔化纤维中氧含量控制在11 wt%以下.高温处理过程中发生自交联:Si—OH间脱水生成Si—O—Si;Si—H与Si—OH或Si—CH3脱氢生成Si—CH2—Si.

A series of spinnable polyaluminocarbosilane（ PACS） with different Al contents were prepared from different ratios of low-molecular polycarbosilane（ L-PCS） and aluminum acetylacetonate [Al（ Ac Ac）3].The mass distribution and the structure of PACS were investigated. In addition,the oxidation curing behavior of the PACS fibers was studied,in contrast to that of the PCS fibers. The results show that [Al（ Ac Ac）3] was introduced to L-PCS by the formation of the —Al（ Ac Ac）2hanging and the —Al（ Ac Ac） — bridging. The PACS has a bimodal mass distribution,which leads to good spinnability. Both the number and reactivity of Si—H in PACS decreased with the increase of the Al content. Moreover,the Si—OH was prevented from forming the Si—O—Si crosslinking bonds,which were produced by the oxidation of Si—H. As the increase of Al content,the gel-point temperature was retarded to high temperatures and the gel content increased slowly with the elevation of temperature. Consequently,excessive oxygen was introduced into the cured fibers. By means of preoxidation and self-crosslinking,the oxygen content of cured PACS fibers was reduced under 11 wt%. The self-crosslinking mechanism includes the following two ways. Firstly,the activated Si—OH reacts with each other to form Si—O—Si by releasing H2 O. Secondly,Si—H reacts with Si—OH or Si—CH3to form Si—O—Si or Si—CH2—Si by releasing H2.