High molecular weight polycarbosilane and preparation method thereof

Abstract

The invention relates to high molecular weight polycarbosilane and a preparation method thereof. The method comprises the following steps: distilling polydimethylsilane, mixing the distilled polydimethylsilane with reducing metal powder, then heating up to 320-360 DEG C and carrying out heat preservation for 3.8-4.2h, and then cooling to room temperature to obtain a liquid split product-polysilane; adding divinyl benzene and polymetylhydrosiloxane, heating up to 320-360 DEG C, and carrying out heat preservation for 1.8-2.2h; then, heating up to 420-460 DEG C, carrying out heat preservation for5-7h, and then cooling to room temperature to obtain a polycarbosilane crude product; dissolving the crude product in xylene, filtering, and then introducing nitrogen; after that, heating up to 420-460 DEG C, carrying out heat preservation for 1.8-2.2h, and then cooling to 320-360 DEG C to obtain the high molecular weight polycarbosilane. The preparation method provided by the invention is simplein technology, low in requirements for equipment and easy in implementation of batch synthesis; the product is high in molecular weight and purity, and the synthetic yield reaches 70 or above.

Description

technical field [0001] The invention belongs to the technical field of silicon carbide ceramic materials, and in particular relates to a high molecular weight polycarbosilane and a preparation method thereof. Background technique [0002] In recent years, SiC ceramic fibers have shown good application prospects in aerospace, weaponry and other fields due to their ultra-high strength and modulus, excellent high temperature resistance, oxidation resistance, and corrosion resistance. Among them, the precursor conversion method is an effective method for preparing SiC ceramic fibers. The precursor conversion method is to use the excellent fluidity, formability, processability and structural designability of polymers to form ceramic materials. Polycarbosilane (PCS) is the earliest precursor used to prepare SiC fibers. In 1975, Yajima of Japan used polycarbosilane to prepare SiC fibers for the first time and used them in production, creating a new method for preparing inorganic ...

AI Technical Summary

Problems solved by technology

[0006] But domestic PCS still has a lot of deficiencies

Domestic PCS itself is rich in carbon, and the SiC fiber prepared from it has high free carbon content and poor high temperature stability; the content of reactive groups such as Si-H in PCS is low and the activity is low, and it needs to be infused in the air before the fiber is fired. , introducing a large amount of oxygen, the SiC fiber thus prepared has a high oxygen content; PCS lacks a high molecular weight part that is beneficial to improve the fiber strength, and the molecular weight and its distribution are unreasonable, which is unfavorable for improving the performance of the SiC fiber; and the synthetic PCS precursor produces The rate is low, resulting in the high cost of polycarbosilane synthesis

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