Silicone pressure sensitive adhesive is a special adhesive composed of silicone resin (commonly used MQ silicone resin), silicone rubber, catalyst, crosslinking agent and other additives. Silicone pressure sensitive adhesives mainly include solvent type, high solid content type, solvent-free type, emulsion type, radiation curing type, resin modified type, biodegradable type, functional type and other systems.

Since the solvent type contains a large amount of volatile organic compounds, during curing, the volatilization of the solvent will easily cause serious pollution to the environment. Nowadays, more and more attention is paid to environmental protection. The silicone pressure-sensitive adhesive industry is developing with environmentally friendly and low-cost products as the mainstream, and new products such as biodegradable and radiation-curable as the research direction. MQ silicone resin mainly plays the role of tackifying and reinforcing. The silyl hydroxyl group or vinyl group in the MQ resin can react with the hydroxyl group of the silicone rubber or through the hydrogen-containing siloxane and the silicone rubber under the action of a catalyst. Silicone pressure sensitive adhesive.

The indicators to measure the adhesive performance of pressure-sensitive adhesives are tack (tack) T, adhesion (adhesion) A, cohesion (cohesion) C and keying force (keying) K. To obtain pressure-sensitive adhesives with excellent performance , we must consider how to make the four adhesive forces satisfy the following equilibrium relationship: K>C>A>T. The research shows that the ratio of silicone resin to rubber material has the greatest influence on the performance of pressure-sensitive adhesive. With the increase of the amount of silicone resin, the cohesive force of the pressure-sensitive adhesive increases, but the peel force decreases; But the stickiness is reduced. This is because silicone rubber can increase the fluidity of the pressure-sensitive adhesive, thereby increasing the interfacial adhesion and strong initial viscosity; the reduction in the amount of resin is not conducive to deep cross-linking, the reinforcement effect is poor, and the cohesion is reduced. The molecular weight of MQ resin has a great influence on the adhesive performance of pressure-sensitive adhesive, because the change of molecular weight makes the viscosity and cohesive strength of pressure-sensitive adhesive change. When the molecular weight is high, the pressure-sensitive adhesive has high cohesive strength and good stickiness; when the molecular weight is low, its bulk viscosity is low, which can improve the interfacial adhesion, but the polymer cohesive strength is low, and it is prone to cohesive damage when peeled off. When the molecular mass distribution of MQ resin is wide and the number average molecular mass is around 3000, it can be used to prepare pressure sensitive adhesive. Nicolas studied the adhesion properties of acrylic adhesives to silicone elastomers containing different qualities of MQ silicone resin to adjust the mechanical properties (mainly peel strength) of tapes. The results show that the amount of MQ silicone resin in the elastomer has a great influence on the properties of the modified tape, and controlling the surface properties of the elastomer is an effective method to adjust the peel force.

Other applications

It can be used to prepare high temperature and strong alkali-resistant silicone defoamer, and the defoamer also has the advantages of non-toxicity and environmental protection. By adding high-viscosity hydroxy silicone oil and MQ silicone resin to synthesize a network polymer with a high degree of branching, so as to improve the high temperature resistance and strong alkali resistance of the defoamer. Using MQ silicone resin containing SiH group or aralkyl group as cross-linking agent, and under the action of platinum catalyst, the encapsulation material containing phenyl silicone resin was synthesized with silicone resin containing vinyl group and high phenyl group. It has good transparency, high hardness and high refractive index, and can be used for LED packaging and lens production. Using MQ hydrogen-containing silicone oil and silyl alkenoate, under the catalysis of Pt, a hydrosilylation reaction occurs to obtain MQ resin-modified carboxyl silicone oil. Combined with amino silicone oil emulsion, it can give fabrics better softness, smoothness and plump hand.