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Feb 1, 2021
Silicone rubber spherical powder is a kind of true spherical silicone elastomer powder with an average particle size of 0.5-50 μm. Figure 1 is an electron micrograph of silicone rubber spherical fine powder with an average particle diameter of 10 μm. In addition to the basic properties of silicone rubber, this elastomer powder can control its particle size, crosslink density, introduce modified genes, or compound with various functional materials during the manufacturing process, so it can have many special functions ; Mainly used as modifier of synthetic resin, surface modifier of paint, additive of cosmetics and fiber, leather treatment agent, etc.Preparation of Spherical Methyl Silicone Rubber Powder
The general preparation method of the spherical micro-powder of methyl silicone rubber is to emulsify the liquid silicone rubber to prepare an oil-in-water (O/W) emulsion; then vulcanize the dispersed phase to form a dispersion of the spherical micro-powder of silicone rubber, then demulsify and filter ,dry.
The average particle size of the spherical fine silicone rubber powder can be controlled by the average particle size of the particles in the liquid silicone rubber emulsion. Generally, the average particle size of the particles in the emulsion is basically the same as the average particle size of the final silicon rubber powder. The hardness of silicone rubber spherical powder can be changed from liquid.
The cross-linking density of silicone rubber or the amount of filler is adjusted,--generally it is characterized by the hardness of silicone rubber after vulcanization.
Preparation of spherical micropowder of addition vulcanized silicone rubber
Considering the ease of emulsification and the performance of silicone rubber spherical micropowder, the base polymer should choose a vinyl-terminated polydimethylsiloxane with a viscosity (25 C, the same below) 50~ .10000 mPa. s; the crosslinking agent should contain SiH -Based polysiloxane, the amount should be calculated according to the ratio of the SiH group in the crosslinking agent to the amount of SiCH=CH2 in the base polymer [n(SiH)/n(SiCH-CH2)] is 1.0~2.0; The surfactant should be a non-ionic surfactant that has no inhibitory effect on the platinum catalyst, and its hydrophilic-lipophilic balance (HLB value) is 10-15, and it is best to choose two kinds of surfactants with HLB value in combination.
For example: 100 parts viscosity 200 mm2/s, (CH)2 siO chain link mole fraction 96%, (CH2 =CH)(CH;)SiO chain link mole fraction 4%, (CH2-CH)(CH)2SiOus chain link In the end-capped base polymer, add 1 part of viscosity 28 mm2/s, (CH3)3SiO.s block end, (CH) HSiO link 95% mole fraction, (CH3)2SiO link mole fraction 5% Polymethylhydrogensiloxane; After mixing, add 3 parts of polyoxyethylene octyl ether with HLB value of 13.5 and 587 parts of deionized water. After mixing with a high-speed mixer, homogenize with a homogenizer at 30 MPa , Made into O/W type emulsion with an average particle size of 2 μum. Then, add chloroplatinic acid/olefin complex equivalent to 0.001 parts of platinum to 100 parts of the emulsion; after mixing, place it at 20 C for 20 h for addition-crosslinking reaction. Then, heat the emulsion to 85 C, add 5 parts of sodium sulfate, stir and mix to break the emulsion; use a 400 mesh filter to centrifuge and dehydrate
Silicone rubber refers to a rubber in which the main chain consists of alternating silicon and oxygen atoms, and two organic groups are usually attached to the silicon atoms. Ordinary silicone rubber is mainly composed of silicone chain links containing methyl groups and a small amount of vinyl groups. The introduction of phenyl groups can improve the high and low temperature resistance of silicone rubber, while the introduction of trifluoropropyl and cyano groups can improve the temperature and oil resistance of silicone rubber. Silicone rubber has good low-temperature resistance and can generally work at -55°C. After the introduction of phenyl, it can reach -73°C. Silicone rubber also has outstanding heat resistance. It can work for a long time at 180°C, and can withstand a few weeks or longer when it is slightly higher than 200°C, and it can withstand high temperatures above 300°C instantly. Silicone rubber has good air permeability, and its oxygen transmission rate is the highest among synthetic polymers. In addition, silicone rubber also has outstanding characteristics of physiological inertness and will not cause blood coagulation, so it is widely used in the medical field.