Synthesis And Characterization Of Heat-resistant Boron-containing Phenyl Silicone Oil

Semiconductor circuits and aerospace fields have new requirements of silicone materials when working in high-temperature environmental areas.However,the thermal stability of silicone materials currently on the market is difficult to meet this requirement.The preparation of polysiloxane materials with excellent heat resistance at present is a hot research direction.In this paper,boron-containing phenyl silicone oil,boron-containing hydrogen-containing silicone oil,and boron-containing phenyl silicone rubber with excellent heat resistance are synthesized.?1?Boron-containing phenyl silicone oil?BCPSO?synthesized by a balanced catalytic reaction using phenylboronic acid,dimethyldichlorosilane,and diphenyldichlorosilane as raw materials and concentrated sulfuric acid as catalyst.The effect of different phenyl content and boron content on heat resistance of silicone oil was investigated.The results revealed that when the molar ratio of diphenyldichlorosilane and dimethyldichlorosilane was 1:7,and the molar ratio of phenylboronic acid and mixed silane was 1:10,the heat resistance of BCPSO was the best.The temperature at mass loss of 5%?T₅?of BCPSO in a nitrogen and air were435?and 386?,respectively.The chemical structure of BCPSO was characterized by nuclear magnetic resonance spectroscopy?NMR?and fourier transform infrared spectroscopy?FTIR?.The thermal decomposition activation energy of BCPSO in nitrogen atmosphere was more than 220.76 k J·mol^-1by using WFO and Kissinger equation.The thermal decomposition mechanism of BCPSO in air was investigated by thermogravimetric and infrared combined technology.It was found that in the initial stage of thermal decomposition,boron atoms on the main chain of BCPSO had empty electron orbitals could conjugate with the electrons of peroxide radicals,and a temporarily stable intermediate of BCPSO was formed which improved the thermal stability of BCPSO.?2?The boron-containing phenyl silicone rubber was prepared by vinyl terminated BCPSO,hydrogen-containing silicone oils with different hydrogen contents and platinum catalyst.The structure of boron-containing phenyl silicone rubber was characterized by FT-IR.When the mass ratio of hydrogen-containing silicone oil?hydrogen content 0.8%?to vinyl terminated BCPSO was 1:50 and the amount of catalyst was 0.1 wt%,the mechanical and electrical properties of silicone rubber were optimal.The tensile strength,elongation at break,shore hardness,volume resistivity and breakdown voltage of boron-containing phenyl silicone rubber were 0.71 MPa,160%,23 degrees,5.46×10¹³?·cm and 32.0 k V·mm^-1,respectively.?3?Hydrogen-containing silicone oil was prepared by the dechloromethane method,and then the hydrogen-containing silicone oil was hydrolyzed and subjected to condensate with phenylboronic acid to prepare boron and hydrogen containing silicone oil.The product structure was characterized by NMR and FTIR.The T₅of the boron and hydrogen containing silicone oil in nitrogen and air were 358?and 346?,respectively,which were 27?and 16?higher than those of the corresponding hydrogen-containing silicone oil.The differential scanning calorimeter?DSC?revealed that the introduction of phenylboronic acid increased the glass transition temperature?T_g?of boron and hydrogen containing silicone oil,from-105?to-98?.