Introduction to UV Adhesive

UV adhesive, also known as shadowless adhesive or ultraviolet adhesive, is a single-component UV-visible light-cured modified acrylic resin adhesive. UV stands for "Ultraviolet Rays," which are invisible to the naked eye and represent a segment of electromagnetic radiation outside the visible light spectrum with wavelengths ranging from 10 to 400 nm. UV adhesive is a type of adhesive that cures only when exposed to ultraviolet light. It can be used as an adhesive and as a material for paints, coatings, and inks.

The curing principle of UV adhesive involves a photosensitizer (or photosensitive agent) within the UV-cured material. When exposed to ultraviolet light, this photosensitizer absorbs UV radiation, generating active radicals or cations. This initiates processes like monomer polymerization, cross-linking, and branching chemical reactions, transforming the adhesive from a liquid to a solid state within seconds.

Characteristics of UV Adhesive

1. Rapid Curing with Controlled Reaction: UV adhesive cures quickly, and the reaction can be controlled.

2. Solvent-Free and Non-Polluting: UV adhesive does not contain solvents, making it an environmentally friendly option.

3. Suitable for Automation: UV adhesive is well-suited for automated processes.

4. Wide Range of Bondable Materials with High Adhesive Strength: It can bond various materials, offering high bonding strength suitable for structural bonding, and has a wide range of applications.

5. Optical Properties: UV adhesive is optically clear and transparent. After curing, it maintains high light transmittance (> 90%) and is often referred to as "shadowless adhesive."

6. Excellent Weather Resistance: UV adhesive is resistant to yellowing and other weathering effects.

7. Limitation: The adherents must allow some degree of light transmission, and UV curing requires specific equipment.

UV adhesive is widely used in industries such as electronics, optics, automotive, and more for its fast curing, versatility, and excellent optical properties.

UV Adhesive Principle

The UV glue can be initially solidified for 1-5 seconds under ultraviolet light and can be bonded in 20-30 seconds. After being irradiated, it can reach a high strength, which can meet the needs of the rhythm of automated production lines; The second-generation acrylate structural adhesive is initially set in 1-10 minutes, and it takes 24 hours to reach its maximum strength; Room temperature curing epoxy structural adhesive has a initial solidification time of 10-120 minutes and can reach its maximum strength after 7 days.

UV adhesive composition

Precursor: 30~50%

acrylate Monomer: 40~60%

Photoinitiator: 1~6%

Additive: 0.2~1%

The precursors include: epoxy acrylates, polyurethane acrylates, polyether acrylates, polyester acrylates, acrylate resins, etc.; the monomers include: single-functional (IBOA, IBOMA, HEMA, etc.), di-functional (TPGDA, DDA, DEGDA, NPGDA, etc.), tri-functional and multi-functional (TMPTA, PETA, etc.); the initiators include: 1173, 184, 907, benzophenone, etc.; and the additives are optional.

UV adhesive advantages 

Environmental safety: 

● No VOC emissions, no pollution to the ambient air;

● Fewer restrictions or prohibitions on the use of adhesive components in environmental regulations;

● No solvents, low flammability.

Economic Benefits:

Fast curing speed, ranging from a few seconds to a few tens of seconds, allowing for automation on production lines and increased labor productivity.

Immediate testing and handling after curing, saving space.

Room temperature curing, saving energy. For example, the energy required to produce 1g of UV-cured pressure-sensitive adhesive is only 1% of that required for water-based adhesives and 4% of that for solvent-based adhesives. UV curing can be used for materials that are not suitable for high-temperature curing, saving 90% of energy compared to thermosetting resins.

Simple curing equipment, requiring only lamps or conveyors, saving space.

Single-component system, no mixing required, easy to use.

Compatibility:

Suitable for materials sensitive to temperature, solvents, and humidity.

Curing can be controlled, and waiting time can be adjusted, allowing for adjustable curing levels.

Multiple rounds of adhesive application and curing are possible.

UV lamps can be easily installed on existing production lines with minimal modifications.