Silicone sealant


Silicone sealant is widely used in electronics, electrical appliances, automotive and other industries. Hechuan Chemical Industry specializes in formulation analysis, composition detection, formulation reduction and formulation detection of silicone sealant. Hechuan Chemical Industry provides a complete set of product formulation improvement technology for adhesive enterprises.


Background introduction


There are many kinds of filling materials, but now most of them are synthetic polymers. Among them, epoxy resin, polyurethane elastomer and silicone polymer are the most widely used polymers. Silicone polymer materials are widely used for the sealing protection of electronic and electrical components because of their special structure of silicon-oxygen bond main chain, unique weather resistance, aging resistance, excellent high and low temperature resistance, good hydrophobic mechanical properties, electrical insulation and so on. Semiconductor light-emitting diode (LED) displays are mostly used for sealing. Filling with silicone.


Product introduction


Composition and Classification of 2.1 Silicone Pouring Adhesive


Silicone sealant is composed of silicone resin, crosslinking agent, catalyst and thermal conductive material. Silicone rubber sealant can be divided into room temperature vulcanized silicone rubber, two-component formed silicone rubber sealant (ARC silicone rubber) and two-component condensed silicone rubber sealant (RTV silicone rubber) according to molecular structure and cross-linking method.


ARC silicone rubber has no release of small molecule, easy control of cross-linking structure, shrinkage rate below 0.2%, electrical properties, elasticity and other advantages over RTV silicone rubber, and superior technological properties, which can be cured at room temperature and in a short time after heating. Therefore, ARC silicone rubber sealant is recognized as a new type of material for electronic industry with great development prospects at home and abroad.


2.2 Dual Component Additive Formed Silicone Rubber Sealant


The common two-component and two-component additional silicone rubber sealant is composed of vinyl-terminated silicone oil as base rubber, hydrogen-containing silicone oil as cross-linking agent and aluminium trioxide (A l2O3) as thermal conductive filler. Methacryloxypropyl trimethoxysilane (KH570) can be added as coupling agent and platinum catalyst (PL-2600) as catalyst.


2.2.1 Curing Characteristics


In this reaction, polysiloxane containing hydrogen functional group is used as crosslinking agent (vulcanizing agent), chloroplatinic acid or its soluble platinum compound as catalyst. Sulfidation is carried out at room temperature without releasing by-products, so the addition of formed silicone gel does not shrink during the curing process. This kind of vulcanizate is non-toxic, has excellent hydrolysis resistance, good low compression deformation, low combustion, deep vulcanization, vulcanization speed can be controlled by temperature and so on.


Effect of particle size of 2.2.2 thermal conductive material on properties of encapsulating adhesive


The bigger the particle size of A l2O3, the bigger the thermal conductivity, but the smaller the tensile strength and elongation at break. The suitable particle size of Al2O3 is 5 or 18 microns. With the increase of the amount of Al2O3, the thermal conductivity and tensile strength of the encapsulating adhesive increase, the elongation at break increases first and then decreases, and the suitable amount of Al2O3 added to increase the viscosity is 150-200 phr. When the mass ratio of 18-micron Al2O3 to 5-micron Al2O3 is 3:2, the thermal conductivity of the filling adhesive is higher, and it has little effect on the viscosity and mechanical properties of the filling adhesive.


Effect of 2.2.3 Silane Coupling Agent on the Properties of Pouring Adhesive


Taking KH570 as an example, adding KH570 can improve the mechanical properties of encapsulation adhesive, but the thermal conductivity decreases slightly. The appropriate dosage is 0.5% of Al2O3.


From Hechuan Chemist