| Liquid silicone rubber is a kind of silicone elastomer, on the basis of polysiloxane complex and silicon-oxygen key as the main chain. The liquid silicone has a series of characteristics, such as good heat-conducting property,excellent mechanical properties, aging-resistant, insulation, which is widely used in the areas of electronic seal and seal pipe, construction, medical equipment, the keyboard and baby supplies. With the development of society,the liquid silicone rubber with single functionality have been unable to meet the market demand, the versatility of liquid silicone rubber with good chemical stability is get more attention from the society.Silazane is organic polymer with main chain of silicon and nitrogen containing, Compared with polysiloxane, polysilazane has high reactivity and high heat resistance temperature.But the lack of the suitable preparation methods for polysilazane with high molecular weight and linear main chain,the potential application value of polysilazane is far from the effective development. In the past 10 years, as the important raw material of ceramic precursor and the preparation of silicon nitride, Poly silazane synthesis got the tech world high attention. Polysilazane as an important part of organic siliconpolymer, which is a good kind of organic silicon nitrogen compound reinforcing filler, this paper based on the research train of thought of the polysilazane as the liquid silicone rubber reinforcing filler to synthesis of heat resistant type liquid silicone rubber, provide theoretical basis for the synthesis of functional liquid silicone rubber.This paper use thermodynamic properties of silazane, In order to design the molecular structure of the target, catalyzed synthesis of N-methyl silazane by anionic ring opening polymerization, the synthetic products as the reinforcing filler, under the action of alkaline catalyst, directional synthesis and structural characterization, Synthesis of the high molecular weight N-polysilazane liquid silicone rubber with regular structure, and then discusses the effect of high molecular weight polysilazane on the heat-resistant property of liquid silicone rubber.The main research content process of this article is as follows:First, by dimethyl dichloride silane and ammonia in ammonia atmosphere,with high purity of toluene as reaction reagent, synthesis of low molecular weight octamethylcyclotetrasilazane, according to the silicon nitrogen bond angle and space, design and controllable synthesis of polysilazane molecules structure, with ruthenium trichloride as catalyst, hexamethyldisilazane lithium as initiator, octamethylcyclotetrasiloxane catalyzed ring opening by adopting the method of anionic ring-opening polymerization, characterization of molecular structure by 1H-NMR and FT- IR and other means, comparing their differences, discuss the ionic ring-opening polymerization efficiency of octamethylcyclotetrasiloxane in different temperature, reaction time and different ion catalyzed ring opening conditions, choose a better structure for the next step of silicone rubber crosslinking reaction.The second,on the basis of polysiloxane, synthesis of liquid siliconerubber by adding different proportion homemade silazane in turn, researching on various influencing factors of the performances of silicone rubber heat-resistant, and studying the molecular structure of polyethylene silazane on the basis, researching the influence of polysilazane molecular structure and the dosage of additives on the heat resistant properties of silicone rubber at room temperature, provides effective theoretical basis for the development of N-methyl polyesilazane liquid silicone rubber with heat resistant properties.The last, characterization of molecular structure and testing polymer heat resistant performance by using IR, NMR, GPC, DSC, TG, exploring the relationship between silazane product structure and silicone heat resistant properties, obtained new siloxane-silazane block copolymer than silicone rubber thermal decomposition temperature of 100 ? or more, provide technical support in the synthesis of silicone rubber with good thermal stability versatility.Through the experimental design, structure characterization and properties analysision, the conclusion is as follows:Dimethyl dichloride silane and ammonia in ammonia atmosphere, with high purity of toluene as reaction reagent, synthesis of low molecular weight of octamethylcyclotetrasilazane, characterization of the product structure,in accordance with the basic design structure, the molecular weight of the product is low;Under the condition of 160 ?, the octamethylcyclotetrasilazane as reaction monomers, ruthenium trichloride as catalyst, hexamethyldisilazane lithium as initiator, anionic catalytic ring-opening of ring silazane reaction,characterization of the molecular structure of ion catalyzed ring-opening products, the main chain neat in structure, in accordance with the basic design structure;The octamethylcyclotetrasilazane as reaction monomers, adding tetramethylcyclotetrasiloxane, methylphenylcyclosiloxanes and N-methyl polysilazane in turn, under the condition of high temperature with alkaline catalyst for catalytic polymerization, cool to room temperature, getting the colorless and transparent liquid silicone rubber;Heat resistance and thermodynamic properties of liquid silicone rubber is gradually increasing with the increase of N-methyl polysilazane, and present a good positive correlation, the liquid silicone rubber with 0%, 5%, 10%, 15%proportion of the N-methyl polysilazane, the maximum weight loss rate of temperature is 280?, 387.5?, 425?, 443.75 ? respectively, when the proportion of N-methyl polysilazane reach 20%, due to the large viscosity of ontology, the liquid silicone rubber adhesive for solid. Comprehensive analysis,the appropriate proportion of N-methyl polysilazane can effectively improve the heat resistance and thermal stability of liquid silicone rubber;... |
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