Light curing technology is a high-efficiency, environmental protection, energy-saving and high-quality material surface technology. It is known as a new technology for green industry in the 21st century. With the development of science and technology, the application of light curing technology has developed from the earliest printed board and photoresist to light curing coating, ink and adhesive. The application field has been expanding and formed a new industry.
The most common UV curing products are UV coatings, UV inks and UV adhesives. Their biggest feature is that they have a fast curing rate, generally between a few seconds and tens of seconds. The fastest can be cured in 0.05 ~ 0.1s. They are the fastest drying and curing among various coatings, inks and adhesives at present.
UV curing is UV curing. UV is the English abbreviation of UV. Curing refers to the process of changing substances from low molecules to polymers. UV curing generally refers to the curing conditions or requirements of coatings (paints), inks, adhesives (glues) or other potting sealants that need to be cured by UV, which is different from heating curing, bonding agent (curing agent) curing, natural curing, etc. [1].
The basic components of light curing products include oligomers, active diluents, photoinitiators, additives and so on. Oligomer is the main body of UV curing products, and its performance basically determines the main performance of cured materials. Therefore, the selection and design of oligomer is undoubtedly an important link in the formulation of UV curing products.
What these oligomers have in common is that they all have “Unsaturated double bond resins are ranked according to the reaction rate of free radical polymerization: acryloyloxy > Methacryloyloxy > vinyl > allyl. Therefore, the oligomers used in free radical light curing are mainly all kinds of acrylic resins, such as epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, acrylate resin or vinyl resin, and epoxy acrylate is the most widely used Acrylic resin, polyurethane acrylic resin and polyester acrylic resin. These three resins are briefly introduced below.
Epoxy acrylate is the most widely used and used light curing oligomer. It is prepared from epoxy resin and (meth) acrylate. Epoxy acrylate can be divided into bisphenol A epoxy acrylate, phenolic epoxy acrylate, modified epoxy acrylate and epoxidated acrylate according to the structural type. Bisphenol A epoxy acrylate is the most widely used. Bisphenol A epoxy acrylate is one of the oligomers with the fastest light curing rate. The cured film has high hardness, high gloss, excellent chemical resistance, good heat resistance and electrical properties. In addition, bisphenol A oxygen exchange acrylate has simple raw material formula and low price. Therefore, it is commonly used as the main resin of light curing paper, wood, plastic and metal coatings, as well as the main resin of light curing ink and light curing adhesive.
Polyurethane acrylate
Polyurethane acrylate (PUA) is another important light curing oligomer. It is synthesized by two-step reaction of polyisocyanate, long-chain diol and hydroxyl acrylate. Due to the multiple structures of polyisocyanates and long-chain diols, oligomers with set properties are synthesized through molecular design. Therefore, they are the oligomers with the most product brands at present, and are widely used in light curing coatings, inks and adhesives.
Polyester Acrylate
Polyester acrylate (PEA) is also a common oligomer. It is prepared by acrylate of low molecular weight polyester glycol. Polyester acrylate is characterized by low price and low viscosity. Due to its low viscosity, polyester acrylate can be used as both oligomer and active diluent. In addition, polyester acrylates mostly have low odor, low irritation, good flexibility and pigment wettability, and are suitable for color paints and inks. In order to improve the high curing rate, multifunctional polyester acrylate can be prepared; Amine modified polyester acrylate can not only reduce the influence of oxygen polymerization inhibition and improve the curing rate, but also improve the adhesion, gloss and wear resistance.
Active diluents usually contain reactive groups, which can dissolve and dilute oligomers, and play an important role in the light curing process and film properties. According to the number of reactive groups contained, common monofunctional active diluents include isodecyl acrylate, lauryl acrylate, hydroxyethyl methacrylate, glycidyl methacrylate, etc; Bifunctional active diluents include polyethylene glycol diacrylate series, dipropylene glycol diacrylate, neopentyl glycol diacrylate, etc; Multifunctional active diluents such as trimethylolpropane triacrylate, etc.
Initiator has an important influence on the curing rate of UV curing products. In UV curing products, the addition amount of photoinitiator is generally 3% ~ 5%. In addition, pigments and filler additives also have an important impact on the final properties of UV cured products.
Post time: Apr-20-2022
