The key additive for the next generation of UV resins: Thiol makes the formula

 

In the pursuit of higher efficiency and greater stability in UV-curable material formulations, the role of "sensitizer" has attracted increasing attention. Among them, thiol compounds (containing sulfhydryl groups) have been shown to significantly enhance the performance of conventional UV-curable resins. Thanks to their excellent radical-donating capability and oxygen-inhibition suppression properties, thiols effectively address multiple limitations in curing speed, stability, and surface quality.

 

 

This article will describe the application principles, key data, and advantageous mechanisms of thiol-based sensitizers, as well as their practical application potential in high-performance UV-curable systems.

 

 

Technical Pain Points and Development Challenges

 

In conventional UV-curable systems, common issues include:

 

• Insufficient curing speed: particularly under LED or low-intensity UV light sources, where performance is less satisfactory.
• Pronounced oxygen inhibition effect: leading to incomplete surface curing and deterioration of coating properties.
• Yellowing phenomenon: caused by prolonged exposure or residual unreacted photoinitiators, resulting in discoloration.
• Poor adhesion: especially on plastics or inorganic substrates, where stronger chemical bonding is required.

 

All of these pain points can be effectively addressed through the proper incorporation of thiol-based sensitizers.

 

 

 

 

Mechanism Analysis: Three Key Function of Thiols

 

1. Accelerated Radical Reactions for Faster Curing

Thiols can interact with free radicals, significantly increasing the double-bond conversion rate and thereby accelerating the curing process.

 

2. Oxygen Inhibition Suppression for Enhanced Environmental Friendliness

Conventional UV-curable materials are prone to oxygen inhibition, leading to an uncured surface layer when processed in air. Thiols, however, can react with oxygen or convert into reactive species, effectively sustaining the curing reaction.

Whether the monomers are acrylates or vinyl ethers, thiol incorporation enables stable curing under ambient conditions, thereby broadening application possibilities.

 

3. Improved Yellowing Resistance and Adhesion Performance

Residual photoinitiators are one of the major causes of yellowing in UV-curable systems. By reducing the required photoinitiator concentration, thiols help mitigate yellowing while simultaneously improving adhesion to various substrates.

 

 

Application and Formulation for Reference

 

Component	Loading (phr)
Acrylate Monomer (TMPTA)	100
Photoinitiator (1-hydroxycyclohexyl-phenyl ketone)	0.1–2
Thiol-based Sensitizer (e.g., PEMP)	2–10

 

 

Processing Recommendation:

Adjust the formulation according to the desired curing speed and adhesion performance, and select low-odor or low-viscosity grades to enhance user-friendliness.

 

 

Application Outlook: From Formulation Engineering to Industrial Practice

 

With the increasing adoption of LED UV-curing equipment and the growing demand for solvent-free, environmentally friendly formulations, thiol-based sensitizers not only provide technical reinforcement but also expand the boundaries of UV-curable applications. Specific applications include:

 

• Optical films and coatings (e.g., anti-reflective layers, protective coatings)
• Medical-grade adhesives and coatings
• High-adhesion electronic encapsulation materials (e.g., UV underfill)
• Functional coatings on plastic surfaces (e.g., PMMA, PC)

 

Thiol-based sensitizers are not a replacement for conventional photoinitiator systems, but rather a systematic upgrade tool that strengthens reactions, stabilizes mechanisms, and enhances product quality. Through precise selection and rational formulation design, they can help R&D teams significantly improve the performance of UV-curable materials.

 

If you are seeking a qualitative breakthrough in UV resin formulations, consider starting with the incorporation of thiol-based sensitizers.

 

 

 

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