The Applications of MQ Silicone Resin
MQ Silicone in Cosmetics
Methyl MQ silicone resin is used as a protective film forming agent for skin and hair surface, which is combined with dimethyl siloxane for cosmetic use as a surface protective coating film to eliminate the stickiness of silicone oil and improve its slippery, scratch-resistant and lustrous. It can also be used to prepare shampoo and skin cream.
MQ Silicone in Defoamer
Ordinary silicone defoamer is generally emulsified by high temperature treatment with methyl silicone oil and hydrophobic white carbon black. The white carbon black dissolves quickly into sodium silicate in strong alkali and high temperature environment, and puncture under white carbon black.
At the tip of the foam, the methyl silicone oil that loses the tip of the needle inevitably leads to a decrease in the ability to eliminate and inhibit foaming. On the other hand, the linear molecules of methyl silicone oil gradually break in a strong alkali and high temperature environment to form a small molecule without defoaming ability. At present, there are many reports on the emulsification of silicone antifoam actives. However, the emulsification only disperses the antifoaming active in water, which has little effect on the defoaming and antifoaming properties, and the defoaming active is the defoaming agent. Determinants of elimination and inhibition performance.
The high-viscosity hydroxy silicone oil and MQ silicone resin are mainly used to synthesize a highly branched network polymer, thereby improving the high temperature resistance and alkali resistance of the defoaming agent. The effects of MQ silicone resin mass fraction and M/Q ratio, reaction time and catalyst mass fraction on the performance of defoamer were discussed.
1)The M/Q ratio of MQ silicone resin has a great influence on the antifoaming performance of the defoaming agent. The silicone resin with M/Q=0.68 can enhance the foam suppression performance. The residual Si-OH group remaining in the MQ silicone resin and the residual Si-OH on the hydroxy silicone oil and the partially hydrophobic silica can undergo complex chain scission, condensation and cross-linking reactions under strong base catalysis to form branched chains. a polymer in a spatial network structure. The structure and molecular mass of MQ silicone resin are determined by the M/Q ratio. The smaller the ratio, the more complex the spatial network structure is, which is more conducive to improving the antifoaming performance of the defoamer. However, the M/Q ratio is too small, which is difficult. Soluble in methyl silicone oil and cannot be used.
2) When the mass fraction of MQ silicone resin is greater than 10%, there is no significant difference in the antifoaming performance of the defoaming agent. The excessive foaming performance is not improved, and too little contributes little to the foam inhibition performance because the formed polymer The degree of crosslinking is too small, which affects the antifoaming performance of the defoaming agent, and it is preferable to select 5-10% in consideration of cost factors.
Reinforcement application of methyl vinyl MQ silicone resin in addition liquid silicone rubber
The addition of silicone rubber is mainly composed of vinyl-containing silicone oil, reinforcing filler, hydrogen-containing silicone oil crosslinking agent and platinum catalyst. Under the action of the platinum catalyst, the vinyl-containing MQ resin can chemically combine with the silicone rubber by a hydrosilylation reaction with the -SiH cross-linking agent, thereby forming a three-dimensional network structure to reinforce.
With the increase of the amount of MQ silicone resin, the hardness, tensile strength, tear strength, adhesive property and crosslink density of silicone rubber are gradually increased to the optimum value, and then gradually decrease as the amount of addition increases. The reason is that the molecular weight of MQ silicone resin is relatively small and the vinyl content is relatively high. It has good compatibility and dispersibility in silicone rubber and chemically combines with silicone rubber. However, when the crosslink density is too large, the cross-linking points are unevenly distributed, stress concentration is formed, the silicone rubber becomes hard and brittle, and the silicone rubber is easily broken under stress.
The curing time is prolonged with the increase of the amount of MQ. This is because the MQ molecule is small and the vinyl content is high, which can preferentially react with the hydrogen-containing silicone oil, thereby delaying the reaction between the silicon-hydrogen and the vinyl silicone oil until the MQ is consumed.
As the amount of MQ resin increases, the dielectric constant of the silicone rubber increases to a maximum value and approaches equilibrium. Since the Si-OH polar group is introduced into the silicone rubber after the hydrosilylation reaction of the MQ resin, the dielectric constant is increased; however, the amount of the MQ resin is too large, and the silicone rubber is excessively crosslinked, which limits the polar group. The activity of the group, so that the dielectric constant tends to be stable. However, the dielectric properties of silicone are still lower than those of ordinary rubber.
As the vinyl content of the MQ silicone resin increases, the tensile strength of the silicone rubber first increases and then decreases, and the elongation at break decreases substantially with the increase of the vinyl content. This is because as the vinyl content in the MQ silicone resin increases, the cross-linking points of the bonds between the molecules are increased, and the tensile strength of the vulcanizate is gradually increased. But when the cross-linking density exceeds a certain value, the tensile strength fell.
Methyl MQ silicone resin is used to improve the viscosity of pressure sensitive adhesive
Purpose: To adjust the peel force of pressure sensitive adhesive
Recommended: M:Q=0.6-0.8 methyl MQ silicone resin
Process: First, the methyl MQ silicone resin is diluted with D4 or D5 into a dispersion of 20-30%, and then proportioned with the silicone rubber, and then add an appropriate amount of a condensation catalyst and a crosslinking agent .
Results: The dissolved MQ silicone resin solution was clear and transparent, and the pressure-sensitive adhesive made had good adhesion.
Evaluation method of holding viscosity: the vertical bonding area of stainless steel surface is 25mm*25mm, the load is 1kg, and it does not fall for 50min.
Adding a certain ratio and quantity of MQ silicone resin to enhance the peeling force and holding force when making silicone pressure sensitive adhesive.
MQ silicone resins contain residual silanol functional groups with a wide glass transition temperature. Silicone resin is added to the silicone pressure sensitive adhesive to thicken the silicone rubber. The tape made of pressure sensitive adhesive with high silicone resin content (MQ/107=2.5) has a good holding capacity of 180 ゚ peeling force, but the initial tackiness is poor. On the contrary, in the viscosity test, the pressure sensitive adhesive with a high content of 107 silicone rubber (MQ/107=1.2) has a good initial tack at room temperature, but the cohesive force is poor, and the tape peels off in a few tens of seconds. When the ratio of silicone to silicone rubber is constant, the properties of the adhesive are affected by the number of silanol groups present in the silicone resin and the silicone rubber. If they do not contain silanol functional groups, they cannot be crosslinked by condensation.