Pressure-sensitive adhesive (PSA) is a soft polymer material with long-lasting adhesion at room temperature. It adheres to the surface of the adherend through non-covalent bonds under light pressure and leaves no residue after being peeled off. Because it has the characteristics of easy adhesion, long-lasting adhesion, peeling without damage and reusable, it is widely used in automobiles, electronics, medicine and industry and other fields.
Among other monomers of pressure-sensitive adhesives, acrylate pressure-sensitive adhesives have become the fastest growing monomer due to their wide variety of monomers, good antioxidant properties, colorlessness, transparency and other characteristics, making them widely used in many fields and develop rapidly.
Acrylic pressure-sensitive adhesive is a copolymer of acrylic monomers and other vinyl monomers. The reason why it can quickly and strongly adhere to solid substrates is that it not only has the fluidity and wettability of liquids, but also has the properties of solids. of cohesion.
Acrylic pressure-sensitive adhesives include solvent-based, emulsion-based, hot-melt and radiation-curing types. Among them, solvent-based pure acrylic pressure-sensitive adhesives are currently commonly used for car clothing backing adhesives.
1. Solvent-based acrylic pressure-sensitive adhesive
Solvent-based acrylic pressure-sensitive adhesive has the advantages of low average relative molecular weight, good wettability, fast drying, high initial adhesion and good water resistance. It has been widely used in pressure-sensitive labels and various forms of tapes. .
This type of acrylate pressure-sensitive adhesive is mainly prepared by free radical polymerization of acrylate monomers and other monomers in organic solvents; in solution polymerization, due to the different chain transfer constants of acrylate monomers in different solvents , so the solvent has a significant impact on the molecular weight and distribution, copolymer viscosity, polymerization reaction speed and chain termination speed. However, in addition to solvents, there are many other factors that have a greater impact on the performance of pressure-sensitive adhesives, including changes in monomer composition and content, polymerization processes, cross-linking agents, cross-linking methods, and additives.
2. Emulsion acrylic pressure-sensitive adhesive
Emulsion acrylic pressure-sensitive adhesive has attracted people's attention due to its advantages of being environmentally friendly, non-polluting, safe to use and low cost. However, it also has a series of problems such as poor bonding strength and water resistance, and slow drying rate, which greatly limits its scope of application. Therefore, the development of emulsion-type acrylic pressure-sensitive adhesives must focus on continuously improving performance and overcoming shortcomings.
3. Hot melt acrylic pressure-sensitive adhesive
Hot-melt acrylic pressure-sensitive adhesive is a copolymer that combines hot-melt and pressure-sensitive characteristics. It is a copolymer polymerized from acrylate monomers and other vinyl monomers. It is also a successor to solvent-based and emulsion-based acrylates. The third generation of pressure-sensitive adhesive products after pressure-sensitive adhesive.
Compared with the former two, hot-melt acrylic pressure-sensitive adhesive does not contain solvents in its production and has a higher solid content. It has the characteristics of faster coating speed, good heat resistance and weather resistance, and is environmentally friendly and pollution-free. ; However, it also has shortcomings such as higher coating temperature, which leads to reduced service life, poor cohesive strength under high temperature conditions, and easy aging by heat and oxygen.
4. Radiation-curable acrylic pressure-sensitive adhesive
Radiation-curable acrylic pressure-sensitive adhesive is a solvent-free pressure-sensitive adhesive. The curing types include electron beam radiation (EB) and ultraviolet radiation (UV). Among them, there are many studies on UV curing. The main component of UV-curable pressure-sensitive adhesive is prepolymer. The characteristics of prepolymer determine the most basic properties of pressure-sensitive adhesive (such as viscosity, hardness and flexibility, etc.). UV curing pressure-sensitive adhesive is prepared by adding a certain amount of photoinitiator, tackifying resin, reactive diluent, etc. to the prepolymer. UV light curing technology has the characteristics of environmental protection, energy saving and high efficiency. It has obvious advantages in being environmentally friendly. It is currently a hot spot in the research of energy-saving and environmentally friendly pressure-sensitive adhesives and has a good development trend.
At present, acrylic pressure-sensitive adhesives are involved in more and more fields. As people and countries pay more and more attention to green chemistry, acrylic pressure-sensitive adhesives will develop in the direction of environmental friendliness, high performance and high intelligence. Since there has been a lot of research on solvent-based and emulsion-based pressure-sensitive adhesives before, the specific focus is to develop solvent-based and emulsion-based pressure-sensitive adhesives into solvent-free acrylate pressure-sensitive adhesives to solve the problem of environmental pollution. At the same time, the basic Conduct modification research on materials or redesign their structures to improve the performance of acrylic pressure-sensitive adhesives. In addition, highly intelligent acrylic pressure-sensitive adhesive is also one of the focuses of future development. In the future, as research continues to deepen, the research and development of new acrylic pressure-sensitive adhesives will receive more and more attention.
