The production level of UV light curable resins has risen significantly to meet Western countries' stringent regulations and to reduce air pollution as well as energy consumption. Over the past forty years, their use and popularity have grown dramatically. UV induced cure has many advantages over traditional cure in terms of lower energy usage and storage for equipment, lower waste, reduced emissions, higher productivity (fast cure), and lower temperature treatment. Therefore, UV curable resins do not usually contain organic solvents that have an adverse environmental effect.
What is UV curing?
Ultraviolet (UV) curing is a photochemical system where high-intensity UV is used in a wide range of industries to rapidly cure inks, coatings, and adhesives. In the process, the first step is the photoinitiators' absorption of UV light from specific wavelengths in the coating, resulting in highly reactive free radicals that begin the resins and monomers cross-linking process.
What are UV curable resins?
Typical UV curable resins consist of oligomers, monomers (which act as diluents), photo-polymerization initiator, co-initiators (spectral sensitizers, reducing agents, etc.) and various additives such as stabilizers, antioxidants, plasticizers, and pigments. The majority of commercial light cure resins are based on free radical curing acrylic compounds (acrylates).
Free-radical curing compositions are the most versatile curing systems regarding product properties and monomers/oligomers available on the market. However, free radical acrylic systems are subject to oxygen inhibition, meaning oxygen in the air can stop the molecules at the surface from polymerizing, leaving a tacky surface layer.
There are multiple commercially available acrylic-functional oligomers like aliphatic and aromatic urethanes, polyester and epoxy resins, silicones and polyether’s. Cationic models based on epoxy and/or vinyl ether chemicals are used in addition to free-radical curing systems. Nonetheless, for light-induced cationic remedy, only a limited amount of monomers and oligomers are usable.
Thus, the versatility in tailoring properties is rather limited. Furthermore, the photoinitiators used in the cationic cure can be somewhat toxic and corrosive. Cationic systems are not subjected to air inhibition but are easily poisoned by moisture in the air.
Where are UV curable resins used?
UV curing resins are used in the paint, ink and adhesive industry for a wide range of applications. Because of their high productivity, ease of application and low environmental impact, they have become very common resin systems. They are often the best choice when it comes to quick-drying and curing. These are commonly used in UV flexo, glass, and lithographic printing inks, overprint varnishes, and potting and encapsulation products for sensitive electronic elements. Other essential applications involve scratch-resistant wood, concrete & plastic coatings, as well as curable acrylic adhesives with UV curability.
UV curing resins are used in the ink, coating, and adhesive industry in a multitude of uses. Because of their high productivity, the convenience of application and low environmental impact, they have become very prevalent resin systems. They are often the ideal choice when it is necessary to dry and recover quickly. They are widely used in UV flexo, display, and lithographic printing inks, overprint varnishes, and potting and encapsulation products for delicate electronic components. Scratch-resistant wood, concrete and plastic coatings or UV curable acrylic adhesives are other significant uses.
Advantages of UV Curing
Composites are typically treated at elevated temperature for relatively short periods, or ambient temperature for longer periods, or some kind of mixture of these. The use of Ultraviolet (UV) power to heal composites provides an option for faster and lower energy use in existing composite production processes. Increased productivity is one of the main advantages of using UV curing, with the healing process taking place under ambient conditions in just a few minutes.
UV curing uses single-component formulations that react only after UV exposure. This can result in an extremely long shelf life, resulting in less waste and higher component efficiency. Besides, volatile emissions (e.g. styrene) can be reduced as the process of curing occurs so quickly and from within the surface. The use of latent single-component epoxy resin formulations is widespread in very distinct areas of implementation with very separate requirements for curable resin attributes. To obtain a balanced property spectrum between reactivity and latency, curing agents with distinctive quality is required for each application.
Environmentally safe UV curable resins
Due to worldwide acceptance of the harmful impacts of volatile organic compounds (VOC), the development of environmentally friendly coatings has attained importance. Many products have been created to minimize VOC emissions, such as waterborne coatings, powder coatings, and radiation-curable coatings.
In addition to being environmentally safe, most of these coatings are cheaper than standard ones. The key features of UV curable coatings are rapid cure time, effective film hardness, and longer shelf life. In addition, the production of coating also involves reduced operating costs, such as low energy consumption and affordable maintenance.
UV curable resins are one of the fastest-growing technologies in the fields of graphic arts, coatings, adhesives, and other related industries. Different end-use product manufacturing companies are now relying on UV curable coatings to achieve customer satisfaction and economic compliance. UV curing technology has less resistance to chemical and physical resistance.
In the UV curable resin market, the development of new and modified photoinitiators is considered to be a relatively new thing. To increase their efficiency, improvements such as expanded photosensitive wavelength band and improved photoinitiator solubility are incorporated with standard photoinitiators. Developing new photoinitiators for UV curing technology requires a huge effort in R&D. Innovation in these materials can help develop more effective curable resins and expand the product range to be cured across end-use sectors.