※ What’s the UV resin?
Ultraviolet-curable (UV) resins are relatively low molecular weight, light-sensitive resins with groups that can undergo light-curing reactions, such as various types of unsaturated double bonds or epoxy groups. Upon irradiation with ultraviolet light, UV resins can undergo chemical changes in a short period of time and rapidly cross-link and cure. The equipment used in the curing process is highly productive, suitable for assembly line production. Curing technology is a new type of green&eco-friendly technology.
※ What are the main types of UV resins?
According to the light curing system, it’s mainly divided into free radical light curing system and cationic light curing system.
Free radical light curing system with oligomer are with “C=C unsaturated double bond” resin, such as acryloyloxy, methacryloyloxy, vinyl, allyl and so on. According to the order of free radical polymerization reaction rate: acryloyloxy > methacryloyloxy > vinyl > allyl. The most used are epoxy acrylate and polyurethane acrylate.
Oligomers for cationic light-curing systems have epoxy groups or vinyl ether groups (CH2=CH-O-), such as epoxy resins and vinyl ether resins.
※ Main chemical types and applications of UV resins
Epoxy acrylate (EA)
Epoxy acrylate is obtained by esterifying epoxy resin and (meth)acrylic acid, and is the light-curing oligomer with the highest market demand. According to the different structure, it can be divided into bisphenol A epoxy acrylate, phenolic epoxy acrylate, epoxidized oil acrylate and modified epoxy acrylate.
Bisphenol A epoxy acrylate is one of the fastest light curing rate among oligomers, with high hardness of cured film, high gloss, excellent chemical resistance, good heat resistance and electrical properties, so it is widely used in light curing ink and various light curing adhesives, as the main resin.
Polyurethane acrylate (PUA)
PUA is an important light-curing oligomer. It is synthesized by reacting polyisocyanate, long-chain diols and hydroxy acrylate.
Polyurethane acrylate molecules contain urethane bonds, can form a variety of hydrogen bonds between the polymer chain, so the cured film has excellent abrasion resistance and flexibility, high elongation at break, at the same time there are good resistance to chemicals and resistance to high and low temperatures, good impact resistance, good adhesion to plastics and other substrates.
PUA is only used in some high-grade performance requirements as the main resin, particularly the double-curing polyurethane acrylate.
Polyester acrylate (abbreviated PEA)
Produced by the acrylation of polyester diols with low molecular weight. Most varieties of PEA have low odor, low irritation, good flexibility and pigment wetting, and are suitable for color paints and inks.
Polyether acrylate definition
Primarily refers to acrylates with polyethylene glycol and polypropylene glycol structures. Polyether acrylate has good flexibility and yellowing resistance, but poor mechanical strength, hardness and chemical resistance, so it is generally not used as the main resin in the light-curing system. It has low viscosity and good dilution, so it can be used as active diluent. Amine-modified polyether acrylate not only has very low viscosity, but also has high reactivity and pigment wettability, which can be used in color paints and inks.
Pure Acrylates
Acrylated polyacrylate or vinyl resins are produced by reacting polyacrylate copolymers with functional groups with glycidyl acrylate or hydroxy acrylate, and attaching acryloyloxy to the side chain. Acrylate oligomers have excellent resistance to yellowing, good flexibility and solvent resistance, and good adhesion to a variety of different substrates, but low mechanical strength and hardness, and poor acid and alkali resistance.
Therefore, pure acrylate oligomer is generally not used as the main resin, just to improve the light-curing coatings, inks, improve yellowing resistance, enhance the adhesion to the substrate and the adhesion between the coating with other resins.
※ How to improve the long-term weatherability of UV resin to prevent it from yellowing and fading?
The selection of UV absorbers and antioxidants is particularly important in UV resins. UV radiation and oxygen are the main causes of the aging of coatings. In order to inhibit or slow down the UV-aging and thermo-oxidative aging of the coating, it’s necessary to add antioxidants, UV absorbers and light stabilizers in coatings. Through these additives, the weathering and durability of the coating can be effectively improved, its service life can be extended, and the quality of the coating can be further improved!
OMNISTAB UV928 has a similar UV absorption spectrum to UV326, so it is a good alternative to UV326 in coating resins.
OMNISTAB UV1130 is suitable for both waterborne and solventborne coatings, and is widely used in automotive and industrial coatings.
OMNISTAB UV384-2 is suitable for coatings exposed to high bake cycles and/or extreme conditions.
OMNISTAB UV400 is a liquid hydroxyphenyl-triazine UV absorber with very high thermal stability and shows high thermal stability and performance for coatings exposed to high bake cycles.
OMNISTAB LS292 is widely used in paint, coating and ink, especially in automotive grade paint. This product has synergistic effect with UV absorber.
OMNISTAB LS123 shows weak alkalinity, which can avoid the reaction with acid components in coatings, which has a wider application.
