MQ silicone resin
MQ silicone resin comes in powder form and is mainly used for reinforcing silica gel. MQ silicone resin is a kind of siloxane, is composed of four functional siloxane polycondensation chain (Q) and single functional siloxane chain (M) composed of silicone resin, its molar mass is generally 1000-8000, the molecular structure of M chain and Q chain ratio and structure determine the properties and application range of silicone resin.


1, MQ resin structure, classification


MQ silicone resin is a kind of unique structure of silicone resin, is composed of silicone compound containing four functional siloxane chain segment (SiO4/2, Q) and silicone compound containing single functional siloxane chain segment (R3SiO1/2, M) co-hydrolysis - condensation reaction to generate a three-dimensional spherical structure of silicone grease. Its molar mass is generally 1000 ~ 8000g/mol, with a state from viscous fluid to solid powder, hard and brittle, and a wide range of glass transition temperature (Tg).


It is generally believed that MQ silicone resin is a dense double layer spherical body, in which the core is Si -- O chain connected, high density, polymerization degree of 15 ~ 50 cage-like SiO2, the shell is r3SiO1/2 layer of low density.


2. Preparation and application of MQ resin


2.1 Application of MQ resin


Product Application:


1, surface treatment agent: such as silicone pressure sensitive adhesive, mobile phone button adhesive, epoxy adhesive surface bonding.


2, reinforcing filler: can be used for RTV rubber, HTV rubber, molding liquid silicone rubber, hot vulcanized rubber, semiconductor components without shell encapsulation, LED encapsulation manufacturing.


3, stickiness agent: used for sealant, silicone resin coating.


4, other additives: such as preparation of film removal agent, defoaming agent, anti-stick agent and light agent, adding molding anti-stick agent peeling force regulator.


5, used for pressure sensitive adhesive, mica tape adhesive, mica plate silicone synthesis.


 


2.2 Application of MQ silicone resin in silicone rubber


Silicone rubber has a variety of excellent properties, but its mechanical properties such as compressive strength and tear strength are poor, which can not meet the requirements of the process. Filler should be added to modify and enhance it. MQ silicone resin as reinforcement filler can not only increase the strength of rubber matrix, but also will not make the viscosity of the system increase too fast, which is conducive to the subsequent operation, and the vulcanized rubber transparency is better. The organic part of MQ silicone resin can improve its compatibility with silicone rubber, play the role of viscosity; Silicon oxygen chain energy saving can improve the mechanical strength, cohesion strength, peel strength and high temperature resistance of silicone rubber, and play a reinforcing role. The additive silicone rubber is mainly composed of vinyl raw rubber, reinforced filler, hydrogen silicone oil crosslinking agent and platinum catalyst. Under the action of platinum catalyst, VINyl-containing MQ resin can chemically bind to the raw rubber through the silohydroaddition reaction with SiH crosslinking agent, thus forming a three-dimensional network structure to strengthen the resin. With the increase of MQ silicone resin dosage, silicone rubber hardness, tensile strength, tear strength, adhesive properties, crosslinking density are gradually increased to the optimal value. The reason is that THE molecular weight of MQ silicone resin is relatively small, the content of vinyl is relatively high, the compatibility and dispersion of silicone rubber is good, and the chemical combination with silicone rubber. However, when the crosslinking density is too high, the distribution of crosslinking points is not uniform, resulting in stress concentration. The silicone rubber becomes hard and brittle, and the silicone rubber is easy to break under the action of stress. The curing time is prolonged with the increase of the amount of MQ. This is because MQ molecules are small and have high vinyl content, which can preferentially react with hydrogen-based silicone oil, thus delaying the reaction of hydrogen silicon and vinyl rubber until MQ is exhausted. With the increase of the amount of MQ resin, the dielectric constant of silicone rubber increases to the maximum value and approaches equilibrium. However, the excessive amount of MQ resin and the excessive crosslinking of silicone rubber limit the activity of polar groups, so that the dielectric constant tends to be stable. However, the dielectric properties of silicone are still lower than ordinary rubber.