Study On The Preparation And Performance Of Phenyl Polysiloxane

Phenyl silicone products as a special category of silicone products,have more excellent performance such as excellent resistance to high and low temperature,radiation resistance,aging resistance than methyl silicone products,so they are widely used in the high-end areas and extreme occasions.The synthetic and application of phenyl silicone products are very different from those of methyl silicone products.They must form their own synthesis and application system and establish various models to design for the products.Phenyl silicone products are ever-changing,and product requirements and application standards of different industries are not the same,in order to better meet the needs of the market and customers,the researchers must do more work.This paper is devoted to the study of the synthesis and application of phenyl silicone products,focusing on the study of the influence of the content of phenyl groups on the refractive index of phenyl polysiloxane,preparation of high performance phenyl silicone,preparation of low gas permeability phenyl silicone rubber,the specific work are as follows:(1)Molecular structure design and synthesis of phenyl polysiloxane.Diphenyldimethoxysilane was used as raw material and acetone as solvent to prepare octaphenylcyclotetrasiloxane.Diphenyldimethoxysilane was completely dissolved in acetone,octophenylcyclotetrasiloxane was slightly dissolved acetone,and octaphenylcyclotetrasiloxane can rapidly separate out.The yield was high and octaphenyl cyclotetrasiloxane purity was of 99.7%.The octaphenylcyclotetrasiloxane containing polychlorinated biphenyls was dissolved in toluene,and the solution was adsorbed with diatomaceous earth,then n-heptane was added to the filtrate,and recrystallization was carried out to make purified octaphenylcyclotetrasiloxane without polychlorinated biphenyls.Phenyl silicone oils were prepared by ring-opening polymerization of methyl silicone oil and phenyl cyclotetrasiloxane,the ring-opening rate was high,and the distribution of groups was more uniform,easy to get transparent products.(2)Study on the effect of phenyl content and molecular structure on the refractive index of silicone polymers and preparation of T-structure phenyl polysiloxane.The effects of phenyl content and group distribution on the refractive index of phenyl silicone oil were investigated by synthesis and characterization of silicone oils of different molecular structures.A group contribution function model was established to predict the refractive index.The refractive index of a phenyl silicone oil is associated with its phenyl content,and increases as the phenyl content increases.A linear relationship between the refractive index and phenyl content had been established.The refractive index values of the phenyl silicone oils calculated from the group contribution method closely match those obtained from the experiments,making the group contribution method a reliable method for predicting the refractive index of a silicone.The refractive index of a phenyl silicone oil will not change with a change in the number of the repeating units of the functional group or the way the functional group distribution in the structure,as long as the molar content remains the same.The T-structure phenylpolysiloxane was designed according to the linear relationship model between the refractive index and the phenyl content,and the optimum conditions were determined.(3)Preparation of high refractive index phenyl silicone resin and LED Packaging Silicone Rubber.Phenyl hydrogen polysiloxanes of different structures were prepared,and LED packaging silicone rubbers were made from these polysiloxanes.The hardness,elongation,tensile strength and anti-yellowing of the LED packaging silicone rubbers on lamps were characterized.The results show that phenyl hydrogen polysiloxanes of resin structures had lower molecular weight,and that the cured silicone rubbers exhibited higher hardness,tensile strength,crosslink density and lower gas permeability.Phenyl hydrogen polysiloxanes of oil structures had higher molecular weight,and the cured silicone rubbers from these polysiloxanes exhibited lower volume expansion coefficient,higher hot and cold impact cycles and less change in hardness during the aging process.The study results further showed that the degree of change in hardness,yellowing,gas permeability,sulfuration and volume expansion coefficient was reduced by using phenyl hydrogen polysiloxanes of resin-oil structures as crosslinking agents,enabling the combined performance advantages of both resin-structure and oil-structure rubbers.Phenyl packaging silicone rubbers had good adhesive strength,shear strength,heat aging,moisture resistance and other properties.(4)Study on the preparation and performance of low gas permeability and high refractive index LED packaging silicone rubber.Following methods were used to reduce the permeability of phenyl silicone rubber: 1)the introduction of high cross-linking structure of the silicone resin;2)the introduction of trifluoropropyl to molecular chain;3)low permeability coating.MT-type phenyl vinyl silicone resin was used as base rubber,and tetramethyl dihydrodiphenyltrisiloxane as crosslinking agent,vinyl-terminated phenyl silicone oil as chain extender to prepare network phenyl silicone resin,which had excellent antisulfuration,resistance to hot and cold impact and heat resistance.Introduction of trifluoropropyl to the molecular chain increased the electron density,reduced the molecular chain rotation ability,and improved the anti-vulcanization performance.The luminous flux was maintained at 93.12% after sulfuration.By using organic polysilazane as low gas permeability coating,the luminous flux was maintained at more than 99.9% after sulfuration.(5)Preparation of optical transparent phenyl silicone rubber reinforced by silica.Phenyl vinyl silicone oil and phenyl hydrogen silicone oil were prepared and had refractive index matching with that of fumed silica.Then optical transparent phenyl silicone rubber was obtained by using fumed silica as reinforcing fillers.Tensile strength,elongation at break,tear strength,heat resistance,anti-vulcanization performance,resistance to thermal shock resistance were tested.The results showed that: 1)After curing,the phenyl silicone rubber had good heat resistance,tensile strength,elongation at break and tear strength;2)antisulfuration capacity was not as good as resin-type phenyl encapsulant,with weak ability to resist gas infiltration;3)excellent resistant to hot and cold impact performance;4)after baking at 300 ? for 8h and instantaneous low temperature impact,phenyl silicone rubber remained intact without cracking,with good toughness and heat resistance.(6)Study on the preparation and performance of low gas permeability trifluoropropyl phenyl silicone rubber.In order to overcome the defects of opacity,high gas permeability,poor heat and solvent oil resistance of methyl silicone rubber,optically transparent trifluoropropyl phenyl silicone rubber was prepared by introducing trifluoropropyl and phenyl to organic silicone molecules.Then organic polysilazane(OPSZ)was coated on the trifluoropropyl phenyl silicone rubber surface with tetramethylhexamethylenediamine as a catalyst and a dense coating with low gas permeability was achieved.This process realized low-temperature curing and siliceous transition.At the same time,optical performance,mechanical properties,oxygen permeation flux,and anti-sulfuration were measured.The results showed that the fluorine-containing phenyl silicone rubber had good optical transparency,tensile strength,elongation at break,tear strength,oil resistance and heat resistance.The OPSZ coating surface was continuous,uniform,dense and free of cracks and voids;meanwhile,the coating section was dense,uniform,seamless,without cracks.The interface between the coating and the silicone rubber exhibited good adhesion.Light transmission was over 92% between 400 and 800 nm.When the coating thickness was more than 12 ?m,the oxygen permeation flux remained unchanged,lamps had good anti-sulfuration ability,and luminous flux was maintained at over 99.9%.when the mass fraction of tetramethyl hexamethylene diamine(w)was over 5%,siliceous transition was achieved under room temperature and 50% relative humidity for 24 h.