Silicone materials in UV-curing combine the properties of both inorganic and organic materials, offering a range of outstanding characteristics—including high light transmittance, resistance to extreme temperatures, resistance to aging, and excellent electrical insulation properties. In the domestic market, a variety of functionalized and differentiated silicone products have been developed, which can be widely applied in areas such as electronic component packaging, sealing of solar panels, thermal conduction of solar cells, potting, shock absorption, and thermal insulation.
Silicone products find wide application in the field of photopolymerization; the following are the primary application areas and key characteristics:
photocureable coating
The soft segment consists of a polysiloxane-based photosensitive prepolymer in the polyurethane coating; the introduction of Si–O bonds significantly enhances the heat resistance, weather resistance, and adhesion of the photopolymerizable coating film.
Enhanced weather and heat resistance: The high bond energy of Si-O bonds in silicone resins endows the coatings with exceptional heat resistance (maintaining stability above 250 °C), as well as outstanding resistance to UV aging and ozone exposure, making them suitable for applications in outdoor architectural and automotive coatings.
Hydrophobicity and stain resistance: The low surface energy of organosilicon compounds ensures that the coating surface is resistant to contamination, as well as to water and oil; when applied to marine coatings or exterior wall coatings, this property helps minimize the adhesion of stains.
Enhanced flexibility and adhesion: The flexibility of the silicone chain segments improves the flexibility of the coating, while the polar groups of the silicone also enhance its adhesion to the substrate, making it suitable for a wide range of substrates, including metals and plastics.
UV-curable adhesive
Rapid curing and high production efficiency: By integrating photopolymerization technology, this silicone adhesive achieves surface drying within seconds, significantly enhancing production efficiency. It is ideal for applications requiring tight production cycles, such as electronic assembly and optical component bonding.
Temperature and Insulation Performance: The material exhibits excellent performance across a wide temperature range (-60 °C to 250 °C) and possesses superior electrical insulation properties, making it suitable for applications—such as electronic and electrical equipment, as well as aerospace—where stringent requirements for insulation and temperature resistance are essential.
Flexibility and Impact Resistance: The flexibility of silicone ensures that the adhesive retains a certain degree of flexibility after curing, enabling it to withstand vibration and impact, thereby reducing the risk of cracking caused by stress concentration.
UV-curable silicone resin
Classification of Silicone UV Resins (5 Major Categories)
- Thiol-olefin-functionalized polysiloxane
This system exhibits rapid light-responsive kinetics, is unaffected by oxygen-induced polymerization inhibition, and can form a soft, elastic cured film. However, the thiol component in this system possesses a strong odor and demonstrates poor storage stability.
(2) Styrenyl polysiloxane
Styrene also exhibits photosensitivity; inexpensive styrene and its derivatives exhibit excellent copolymerization properties with a wide range of resins, thereby enhancing the hardness and mechanical strength of cured films.
This system also exhibits several drawbacks, such as high volatility, high flammability, strong odor, and relatively slow reaction rates; also, its curing performance is inferior to that of other photopolymerization systems.
(3) Vinyl ether-functionalized polysiloxanes
The lone pair of electrons on the oxygen atom conjugates with the carbon-carbon double bond, increasing the electron cloud density of the double bond; consequently, the carbon-carbon double bond in vinyl ethers is an electron-rich double bond, and its reactivity is higher than that of conventional alkene monomers.
These polymers are capable of undergoing free-radical polymerization, cationic polymerization, and charge-transfer complex alternating copolymerization. Consequently, vinyl ether-based polysiloxanes can be utilized in a variety of photopolymerization systems, including free-radical systems, cationic systems, and hybrid systems.
High reactivity, low toxicity, low odor, and high viscosity make photopolymerizable silicone prepolymers an ideal choice; however, the raw material vinyl ether is relatively expensive.
(4) Epoxy-functionalized polysiloxane
During cationic photopolymerization, the strained epoxy groups undergo ring-opening to form strain-free ether bonds, resulting in a very small—or even zero—volume shrinkage; this constitutes one of its key advantages.
Currently, UV-curable epoxy-terminated polysiloxane systems are being increasingly widely applied, establishing themselves as the mainstream product category within cationic photopolymerization systems.
(5) Acrylate-terminated polysiloxane
Acrylate-based photopolymerization systems generally exhibit high photopolymerization reactivity, rapid reaction rates, excellent chemical and physical stability of the cured layer, and a wide range of synthesis routes. By adjusting the formulation, ideal viscosity can be achieved, and these systems also possess certain antioxidant and polymerization-inhibition capabilities. Consequently, they have become the most widely used prepolymer in current photopolymerization products and the most actively researched photopolymerization silicone system.
Comparison of Different Types of Silicone UV Resins
Key characteristics of silicone UV resin:
Toughness Enhancement and Modification: The introduction of silicone segments into resins such as epoxy resins and polyurethane resins can effectively enhance the toughness of the resin, reduce its brittleness, and simultaneously improve properties such as weather resistance and moisture resistance, making it suitable for the fabrication of high-performance composite materials, 3D-printable materials, and other applications.
Low shrinkage and dimensional stability: The low shrinkage characteristic of silicone helps reduce the volumetric shrinkage of the resin during photopolymerization, thereby enhancing the dimensional accuracy and stability of the finished parts. This property makes silicone particularly suitable for applications such as precision molds and optical lenses.
Qi Yusong, Zeng Zhaohua, et al. [21] synthesized a silicone-modified polyurethane acrylate (Si-PUA) prepolymer using hydroxyethyl methacrylate, isophorone diisocyanate, and di(γ-triethoxysilylpropyl)amine as raw materials; the resulting photopolymerized film exhibited excellent electrical and thermal properties.
UV-curable ink
Wear and scratch resistance: Once cured, silicone inks exhibit high surface hardness, along with excellent wear and scratch resistance. They are suitable for applications such as packaging printing and label printing, effectively protecting printed graphics against abrasion.
Rapid drying and high production efficiency: The photopolymerizable silicone ink features fast drying speed, enabling high-speed printing; once cured, the ink exhibits excellent adhesion and solvent resistance, making it suitable for a wide variety of substrate materials.
UV-curable optical fiber coating
In industrial applications, laser fiber low-refractive-index coatings primarily employ UV-curable coatings.
(1) The coating fluid should have moderate viscosity, typically ranging from 2,000 to 5,000 cps; if the viscosity is too high, it will be difficult to achieve proper leveling, whereas if the viscosity is too low, sagging may occur.
(2) The rapid photopolymerization speed enhances fiber drawing efficiency and production productivity; the current industrial standard for fiber drawing is 1,500 m/min, with some applications even reaching speeds exceeding 3,000 m/min.
(3) The refractive index of the cladding after solidification is low—typically less than 1.40—which enables it to work in conjunction with the core layer to achieve a large numerical aperture, while exhibiting low optical absorption and thus not compromising laser transmission within the core layer.
(4) After curing, the material exhibits excellent mechanical properties, including a low Young’s modulus and a low glass transition temperature. These properties enable the outer coating to be softer, allowing it to effectively dissipate stresses within and around the optical fiber, thereby reducing micro-bending loss in the fiber and facilitating the achievement of a smaller fiber winding radius. Also, the material must possess high tensile strength and high elongation at break to prevent the formation of defects during fiber processing and cabling operations.
(5) High adhesion: There should be strong bonding between the coating and the inner encapsulant glass, particularly under the high-temperature and high-humidity operating conditions of fiber laser systems, where this adhesion must not degrade.
(6) Excellent high-temperature resistance: for the development of high-power fiber lasers, coatings must remain free of color changes and variations in transmittance after prolonged exposure to high temperatures.
The most widely used low-refractive-index UV-curable coatings in industrial applications are fluorinated acrylate formulations.
UV-curable silicone release agent
This product was introduced relatively late and employs UV light irradiation within a specific wavelength band for cross-linking and curing. Compared to thermosetting silicone release agents, it offers the following advantages:
Neither the reaction nor the coating process requires heating, making this method suitable for substrates—such as PP and PE—that exhibit poor heat resistance, while also resulting in lower energy consumption.
Free of organic solvents, it is environmentally friendly, and poses no safety hazards such as fire or explosion during storage, transportation, or production and processing stages;
It features rapid curing, which can be completed within seconds, significantly enhancing production efficiency;
UV-curable coating equipment occupies a compact footprint, thereby saving production space.
However, due to the high cost of UV-curable silicone release agents and the substantial capital requirements for coating equipment, these agents hold a relatively small market share and are produced by fewer manufacturers compared to conventional condensation-and addition-type silicone release agents.
In summary, by leveraging the high efficiency of photopolymerization technologies combined with the superior properties of silicone materials, silicone-based products have been widely applied across diverse fields—including coatings, adhesives, resins, inks, and optical fiber coatings—thereby providing high-performance, environmentally friendly, and efficient solutions for industry development.
JOME manufactures the UV curing adhesive range in its own factory for customers in more than 30 countries. Readers continuing from A Brief Analysis of Commonly Used UV-Resistant will find the JOME adhesive factory in Shanghai covers the full portfolio, and project questions go to the reach the JOME technical staff.