Study On Preparation And Application Of Tetramethyltetraethylcyclotetrasiloxane

Organic silicon is one of the seven strategic emerging industries and also an important part of the new materials. With the rapid development of national economy, organic silicon polymer materials were widely used because of its incomparable physical and chemical properties such as excellent resistance to oxygen, ozone, flame, moisture, erosion and ultraviolet light, et. al.In recent years, extreme weather frequently occurs with deterioration of the global climate. The cold resistance of the material is required to be enhanced greatly to satisfy the normal production and life of the people who live in the arctic-alpine region affected by extreme weather conditions. Common organosilicon polymer with the chain structure of Polydimethylsiloxane (PDMS) is difficult to meet the demand of low temperature materials in extreme cold weather. When the siloxane side chain or terminal methyl groups (CH3) part is replaced by the ethyl (C2H5) functional group, the crystallization temperature of the polymer will be reduced because of the destruction of the regularity of dimethyl siloxane structure. So the cold resistant performance of the silicone polymer materials can be enhanced.The organic silicon products containing ethyl have very broad application prospects. The most significant application of2,4,6,8-tetraethyl-2,4,6,8-tetramethyl-cyclotetrasiloxane is that they can be used produce ethyl silicone rubber with excellent cold resistance. And it is also used to synthesize special polymers through ring opening polymerization, such as ethyl phenyl and ethyl benzyl polymers.In this paper, high pure2,4,6,8-tetraethyl-2,4,6,8-tetramethylcyclotetrasiloxane can be prepared by hydrosilylation reaction. Main content is divided into four parts:In the first part, we summarized the excess volume, the research progress of hydrosilylation catalysts and polysiloxane low-temperature performance research.In the second part, we measured2,4,6,8-tetramethylcyclotetrasiloxane saturated vapor pressure data, and the density of the binary system of2,4,6,8- tetramethylcyclotetrasiloxane with aromatic compounds which provide important thermodynamic basis of data for the monomer separation and purification.In the third part,2,4,6,8-tetraethyl-2,4,6,8-tetramethyl-cyclotetrasiloxane is prepared by hydrosilylation of2,4,6,8-tetramethylcyclotetrasiloxane and ethylene using HaPtCl6·6H2O catalyst supported on SiO2. The reaction process had the advantages of high conversion rate of raw materials, high selectivity of the targer product and low content of by-product. High purity of2,4,6,8-tetraethyl-2,4,68-tetramethylcyclo tetrasiloxane can be obtained by distillation. The platinum catalyst is not suitable for industrialization owing to expensive. Therefore ruthenium was used as a hydrosilylation catalyst. The effects of the catalyst species (such as cheap ruthenium compound), the dosage and the cocatalyst composition and the synergistic effect of ruthenium catalyst and cocatalyst on the conversion and yield were discussed.In the last part, various contents of methylethyl siloxane groups poly(dimt(?) methylethyl) was synthetized through cationic ring-opening polymerization with respectively hexamethyldisiloxane,1,3-diphenyldisiloxane,1,1,3,3-tetraphenv disiloxane as the end-blocking agent and octamethylcyclotetrasiloxane (?)2,4,6,8-tetraethyl-2,4,6,8-tetramethyl-cyclotetrasiloxane as the monomers. Th(?) structure was characterized by1HNMR, FT-IR etc, and their thermal stability (?) resistance to cold was tested.