Classification and characteristics of UV light-curing resin

Classification and characteristics of UV light-curing resin (I)

Photocurable resin is also called radiation photocurable resin, UV resin, oligomer, referred to as UV resin. The molecular weight is generally greater than 1000, which determines the main properties of the coating.

The commonly used photocurable resins in China now include epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, amino acrylate, acrylate and other acrylates.

Classification and characteristics of UV light-curing resin (II)

Photocurable resin is also called radiation photocurable resin, UV resin, oligomer, referred to as UV resin. The molecular weight is generally greater than 1000, which determines the main properties of the coating.

The commonly used photocurable resins in China now include epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, amino acrylate, acrylate and other acrylates.

Classification and characteristics of UV light-curing resin (III)

Photocurable resin is also called radiation photocurable resin, UV resin, oligomer, referred to as UV resin. The molecular weight is generally greater than 1000, which determines the main properties of the coating.

The commonly used photocurable resins in China now include epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, amino acrylate, acrylate and other acrylates.

Classification and characteristics of UV light-curing resin (IV)

Photocurable resin is also called radiation photocurable resin, UV resin, oligomer, referred to as UV resin. The molecular weight is generally greater than 1000, which determines the main properties of the coating.

The commonly used photocurable resins in China now include epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, amino acrylate, acrylate and other acrylates.

Low energy and high curing speed UV/LED curing series

Low energy and high curing speed UV/LED curing series

At present, the application of UV/LED curing system still has the difficulty of insufficient curing speed. The main difficulties are as follows

LED curing equipment is single wavelength output, there is no efficient initiator for single wavelength (365nm, 385nm, 395nm, 405nm) at present, the initiator effect of mass production and market is not high at single wavelength, resulting in slow curing speed.

LED curing equipment is a cold light source. Most of the LED equipment currently on the market is single long-wave, which is more efficient than traditional mercury lamps and more friendly to heat-sensitive materials. Heat can better promote the occurrence of curing and cross-linking, while LED equipment does not generate heat. Compared with mercury lamps, the curing speed is relatively low.

LED curing equipment does not have the use of high-power devices, low power and low intensity, which will lead to insufficient curing speed.

Through the test of the application laboratory, the ranking of low energy UV/LED curing speed is as follows:

1. Difunctional modified epoxy acrylate has the characteristics of low viscosity and fast curing speed.
2. Difunctional polyurethane acrylate, with fast curing speed, low viscosity, high hardness, wear resistance and scratch resistance
3. Difunctional polyurethane acrylate, with fast curing speed and good toughness
4. Tetrafunctional polyurethane acrylate, with fast curing speed and toughness
5. Trifunctional polyurethane acrylate, with fast curing speed, excellent flexibility and good elasticity
6. Difunctional polyurethane acrylate, with fast curing speed, good adhesion, good solvent resistance, etc.
7. Difunctional polyurethane acrylate, with fast curing speed, good flexibility, impact resistance, etc.
8. Trifunctional polyurethane acrylate, with fast curing speed, high hardness, good toughness, etc.
9. Difunctional polyurethane acrylate, with good adhesion and toughness
10. Difunctional polyurethane acrylate, with low viscosity, fast curing, high hardness, wear resistance and scratch resistance
11. Difunctional modified epoxy acrylate, with high curing speed, high hardness, excellent chemical resistance, etc.

Application scenarios of dual curing:

The obvious advantage of the dual-cure system is that thermal curing can help cure non-planar parts, while UV curing has a higher cross-linking density to improve fullness and gloss, as well as provide excellent chemical resistance; at the same time, the curing time is short, which can greatly improve production efficiency, reduce surface contamination of parts during the production process, and improve the yield rate.

The combination of hydroxyl functional acrylates with acrylates bearing isocyanates (NCO) allows formulators to take advantage of the best of both worlds (thermal and energy cure kinetics). The implementation of this additional reaction can result in coatings with improved weatherability and similar hardness to conventional coatings, but with lower acrylate crosslink density and higher ductility. Another benefit of using this chemistry is that it can overcome light limitations (shadow cure) through energy cure chemistry, as coatings that are not exposed to UV will not cure or will cure incompletely with low energy. In this case, crosslinking can be performed through a two-component cure process.

The advantages of dual curing are:

1. Thermal curing solves the problem of incomplete light curing in shadow areas of pure UV system special-shaped parts
2. Thermal curing improves the problem of incomplete UV curing of solid color coatings under pure UV system conditions
3. Thermal curing system improves the defects of UV system such as large shrinkage, poor adhesion and insufficient toughness.
4. UV system improves the production efficiency and yield rate of traditional two-component PU thermal curing
5. UV system improves the gloss, richness, hardness, chemical resistance, etc. of traditional two-component PU thermal curing

Dual curing classification:

• 2K light curing + heat curing system:

Resin type: light-curing UV resin containing hydroxyl groups, hydroxyl content 1.0%-5.0%

• 1K light curing + moisture curing system:

Resin type: Light-curing UV resin containing NCO, NCO content 5.0%-10.0%

Dual curing process:

• Two-component light curing + heat curing system:

Component A is a hydroxyl light-curing resin + reactive diluent monomer, pigment, filler, and organic solvent.

Component B includes isocyanate curing agent, photoinitiator, thermal curing catalyst, antioxidant, UV absorber, wetting and leveling agent, organic solvent, etc.

• One-component light curing + moisture curing system

Contains NCO light-curing UV resin, active diluent monomer, pigment, filler, initiator, etc.

Based on storage stability considerations, Meilun New Materials currently provides hydroxyl-containing photocurable resins:

UV light curing resin for UV pressure sensitive adhesive/UV laminating adhesive/UV bonding adhesive

When pressure-sensitive adhesive is under appropriate and slow pressure, it produces viscous flow similar to that of liquid, so that the pressure-sensitive adhesive is in close contact with the surface of the adherend and flows into the grooves on the surface of the adherend, increasing the effective contact area and thus generating a certain adhesive force. When the pressure-sensitive adhesive product is peeled off by external force, the pressure-sensitive adhesive exhibits properties similar to elasticity and has a high peel resistance. The greater the peeling speed, the higher the peel strength of the pressure-sensitive adhesive product. The wettability of the pressure-sensitive adhesive on the surface of the adherend can make it close to the surface of the adherend to generate intermolecular forces and sufficient interfacial adhesion.

Resin properties:

1. Strong adhesion to substrate
2. Balance between cohesion and adhesion
3. TG point is less than -35℃
4. Excellent flexibility
5. Excellent viscoelasticity

In addition, special requirements require high light transmittance, excellent weather resistance, strong water resistance, etc.

Test method of adhesive layer:

Viscosity: 1500-6500 cps at 25℃

Film thickness: 25 microns - 175 microns

Test method: 2400 mj/cm2 ^, 2 kg rollers x2, repeated rolling, 180 degree peel strength test after 30 minutes of lamination

UV resin classification and selection principles

Oligomer (UV resin) refers to a low molecular weight polymer containing one or more photopolymerizable groups.

Photopolymerization group: Unsaturated double bond＞C=C＜ Epoxy group:

1. Classification of UV resins

1. Free radical photocurable oligomers, including the following resins:

Epoxy Acrylate

Polyester acrylate

Polyurethane acrylate

Amino acrylate

Pure acrylic resin

Polyether acrylate, etc.

2. Cationic light-curing oligomers, including the following resins:

Epoxy resin

Vinyl ether resin

II. Principles for selecting oligomers
(1) Viscosity: Select appropriate viscosity according to formula design

(2) Photocuring speed: Generally speaking, the higher the functionality, the faster the photocuring speed. Epoxy acrylate has a fast photocuring speed, and amine-modified oligomers also have a fast photocuring speed.

(3) Physical and mechanical properties: hardness, flexibility, wear resistance, tensile strength, impact resistance, adhesion, chemical resistance (acid and alkali resistance), yellowing resistance, gloss, and pigment wettability.

(4) Oligomer glass transition temperature (Tg): The resin with low Tg generally has low hardness and good gloss; the resin with low Tg has good flexibility and impact resistance.

(5) Curing shrinkage of oligomers: Low curing shrinkage is beneficial to improving the adhesion of the cured film to the substrate. As the functionality of the oligomer increases, the cross-linking density increases, and the curing shrinkage also increases.

(6) Toxicity and irritation: Oligomers have a large molecular weight, are mostly viscous, non-volatile, and not flammable or explosive. They are also less toxic and less irritating to the skin.