Adhesives are used everywhere in life, so what exactly are adhesives? Adhesives are usually defined as: natural or synthetic, organic or inorganic substances that can connect two or more parts or materials together through interface adhesion and substance cohesion. , collectively called adhesive , also called adhesive, customarily called glue. Today, let’s talk about the characteristics and applications of different types of adhesives.

Silicone adhesive
Silicone adhesives include two categories: adhesives (including sealants) based on silicone resin or silicone elastomer.
Silicone resin is composed of a spatial network structure of Si-o-Si as the main chain. It is a cross-linked semi-inorganic polymer with organic groups connected to the silicon atoms. It can be further condensed at high temperatures into a highly cross-linked and hard and Brittle resin.
Silicone rubber is a linear polysiloxane with Si-O-si as the main chain (molecular weight ranging from tens of thousands to hundreds of thousands). It forms several cross-linking points under the action of curing agent and catalyst. Elastomer, silicone rubber mainly composed of polydimethylsiloxane, also called silicone rubber.
The former is mainly used for bonding metal and heat-resistant non-metal materials, and the resulting bonded parts can be used in a temperature range of -60 to 250°C. The latter is mainly used for bonding heat-resistant rubber, rubber and metal, and other non-metal materials. , generally can be used at -60~200℃.
Silicone adhesives can be roughly divided into pure silicone adhesives and modified silicone adhesives. Pure silicone organic adhesives are mainly composed of reactive polysiloxane (hydroxyl-terminated silicone rubber, hydrogen-containing or vinyl silicone oil), curing agent, catalyst, filler and additives.
According to the difference in curing reaction, it can be divided into condensation type, free radical initiated type and hydrosilylation type; according to the different composition and function, it can be divided into one-component silica gel, two-component silica gel and silicone pressure-sensitive adhesive.
Silicone adhesives have many superior properties due to their own molecular structure, including cold resistance, heat resistance, aging resistance, water resistance, moisture resistance, high stretch fatigue strength, small permanent deformation, and non-toxicity. In recent years, this type of adhesive has developed rapidly in the country. It has been widely used in electronic appliances, aerospace, construction industry and other fields.

Polyurethane adhesive
Polyurethane adhesive refers to an adhesive containing urethane groups or isocyanate groups in the molecular chain. According to the reaction composition, it can be divided into polyisocyanate adhesives, isocyanate group-containing polyurethane adhesives, hydroxyl-containing polyurethane adhesives and polyurethane resin adhesives.
Polyurethane adhesive has strong adhesion, large initial tack, and wide range of applications. Because -NCO in the molecular chain of polyurethane adhesive can react with a variety of functional groups containing active hydrogen to form interfacial chemical bonds, it has extremely strong adhesion properties to a variety of materials. It can not only bond porous materials, such as foam plastics, ceramics, wood, fabrics, etc., but also can bond a variety of metals, inorganic materials, plastics, rubber, leather, etc. It is an adhesive with a wide range of applications.
Outstanding low temperature resistance is also its unique feature. At extremely low temperatures, general polymer materials transform into a glassy state and become brittle, while polyurethane adhesives can still maintain high peel strength even below -250°C, and their shear strength decreases as the temperature decreases. Rise significantly.
Polyurethane adhesives are mainly used in shoemaking, packaging, automobiles, magnetic recording materials and other fields.