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Method for synthesizing high-melting-point polycarbosilane at normal pressure

A polycarbosilane and atmospheric pressure synthesis technology is applied in the field of atmospheric pressure synthesis of high-melting polycarbosilane, which can solve the problems of difficulty in batch preparation, high solvent dehydration requirements, complicated steps, etc., and achieves easy batch synthesis, improved linearity, Equipment simple effect

Active Publication Date: 2015-07-22
NAT UNIV OF DEFENSE TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the precipitation and classification method requires high solvent dehydration and complicated steps, making it difficult to achieve batch production (see Chu Zengyong, Liu Hui, Feng Chunxiang, etc. Precipitation and classification method to prepare spinning grade high melting point polycarbosilane. Journal of National University of Defense Technology, 2002, 24( 1): 39-43)

Method used

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  • Method for synthesizing high-melting-point polycarbosilane at normal pressure
  • Method for synthesizing high-melting-point polycarbosilane at normal pressure
  • Method for synthesizing high-melting-point polycarbosilane at normal pressure

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Effect test

Embodiment 1

[0023] This embodiment includes the following steps:

[0024] (1) Under the protection of high-purity nitrogen, the solid raw material polydimethylsilane (PDMS) is cracked and converted into liquid polysilane (LPS) in a nitrogen atmosphere at 360 °C;

[0025] (2) Put 200g of the LPS obtained in step (1) in a pyrolysis synthesis reaction kettle under normal pressure, add 10g of polymethylhydrogensilane to the LPS, and replace the gas in the kettle with high-purity nitrogen three times; raise the temperature under the protection of high-purity nitrogen React at 220°C for 6 hours, then program temperature increase (at a rate of 0.2°C / min) to 440°C for 8 hours to obtain a crude product;

[0026] (3) Dissolve and filter the crude product obtained in step (2) in xylene (mass ratio of crude product to xylene is 1:1), distill the filtrate at 350°C, and obtain 118.7g of light yellow resinous PCS precursor after cooling body.

[0027] The product PCS obtained in this example has a mel...

Embodiment 2

[0031] This embodiment includes the following steps:

[0032] (1) with embodiment 1 step (1);

[0033] (2) Put 200g of LPS in the high-temperature pyrolysis synthesis reaction kettle under normal pressure, add 30g of polymethylhydrogensilane to the LPS, replace the gas in the kettle with high-purity nitrogen three times, and raise the temperature to 220°C for 6 hours under the protection of high-purity nitrogen. Then program temperature increase (at a rate of 0.2°C / min) to 430°C for 8 hours to obtain a crude product;

[0034] (3) The crude product was dissolved in xylene (mass ratio of crude product to xylene: 1:1), filtered, and the filtrate was distilled at 350°C. After cooling, 121.1 g of light yellow resinous PCS precursor was obtained.

[0035] The product PCS has a melting point of 255-279°C, a ceramic yield of 62.9wt%, and can be dissolved in organic solvents such as tetrahydrofuran and xylene.

Embodiment 3

[0037] This embodiment includes the following steps:

[0038] (1) with embodiment 1 step (1);

[0039] (2) Put 200g of LPS in the high-temperature pyrolysis synthesis reaction kettle under normal pressure, add 50g of polymethylhydrogensilane to the LPS, replace the gas in the kettle with high-purity nitrogen three times, and raise the temperature to 220°C for 4 hours under the protection of high-purity nitrogen. Then program temperature increase (at a rate of 0.2°C / min) to 420°C for 6 hours to obtain a crude product;

[0040] (3) The crude product was dissolved in xylene (the mass ratio of crude product to xylene was 1:1), filtered, and the filtrate was distilled at 350°C. After cooling, 123.7g of light yellow resinous PCS precursor was obtained.

[0041] The product PCS has a melting point of 259-281°C, a ceramic yield of 63.6wt%, and can be dissolved in organic solvents such as tetrahydrofuran and xylene.

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Abstract

The invention discloses a method for synthesizing high-melting-point polycarbosilane at the normal pressure. The method comprises the following steps: (1) polydimethylsilane is subjected to splitting decomposition under a nitrogen atmosphere of 360 DEG C or above to be converted into liquid polysilane; (2) polysilane is added, the temperature rises to 220-230 DEG C, the reaction is carried out for 4-6 hours, then the temperature rises through programming to 420-440 DEG C, and the reaction is carried out for 6-8 hours; (3) a crude product is dissolved with xylene, filtered, distilled and cooled to obtain a light yellow resinous polycarbosilane precursor. The proper proportion of polysilane is added into a split product LPS of the polydimethylsilane to increase the concentration of a free radical in a reaction system and reduce the reaction temperature, the high-melting-point polycarbosilane is synthesized at the normal pressure, no new group or structure is introduced in the structure of the obtained polycarbosilane, the degree of linearity is improved, the equipment is simple, the safety is high, the batch synthesis is easy to implement, and the synthesis procedures are few.

Description

technical field [0001] The invention relates to a method for synthesizing polycarbosilane, in particular to a method for synthesizing polycarbosilane with high melting point under normal pressure. Background technique [0002] With the development of high technologies such as aviation, aerospace, weapons, and energy, higher and higher requirements are put forward for high-temperature thermal structural materials. Traditional metal materials and polymer materials have been difficult to meet these application requirements. In recent years, with C f / SiC、SiC f Fiber-reinforced silicon carbide-based composite materials represented by / SiC have been widely used in aviation, aerospace, automobiles and other fields because they can maintain high strength and high modulus characteristics at high temperatures, and at the same time, their mass is much smaller than that of metals and alloy materials. . [0003] The preparation of fiber-reinforced silicon carbide matrix composites o...

Claims

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Application Information

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IPC IPC(8): C08G77/60
Inventor 王浩王军简科邵长伟王小宙苟燕子薛金根
Owner NAT UNIV OF DEFENSE TECH
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