Over the past several decades, resins have become a widely used solution for bonding, printing, and coating projects. Ultraviolet (UV) curable resins, in particular, are increasingly popular because of their quick drying ability and versatility. As the world becomes more environmentally conscious, the energy-efficient aspects of these resins are also appealing. UV curable resins are useful as adhesives, coatings, and inks for a wide spectrum of substrates, including plastics, paper, wood, metal, glass, and composite materials.

At Toagosei America, Inc., we take pride in delivering superior solutions customized to each client’s applications, resulting in high-quality UV curable resins. Read on to learn more about UV curable resins, their benefits and capabilities, and how our team can help.

What Are UV Curable Resins?

UV curable resins consist of a mix of oligomers, monomers which act as the diluent, photopolymerization initiators, antioxidants, stabilizers, plasticizers, and more. Each material serves a unique function in the final product.

When users expose UV curable resins to UV, LED, EB or direct natural sunlight, the energy causes polymer chains to form, quickly bonding and creating an adhesion effect to solidify liquid resin. The speed at which UV curable resins harden makes them quite effective for bonding, printing and coating applications.

UV Curable Resin Benefits

Using UV curable resins can shorten the curing time for your project, which can increase production output while reducing costs in the long run. As the resin does not cure until it is under the UV, LED or EB source, you can apply the liquid form in a variety of ways for added versatility, including:

  • Dispensing
  • Inkjet application
  • Screen printing
  • Spraying
  • Curtain coating
  • Flexo or Lithography Printing

Irradiating resins with UV light generates durable components and reliable adhesion. Compared to other materials, these resins produce bonds of higher strength. As an added benefit, when used as a form of coating, UV curable resins maximize the chemical and wear resistance of a part to safeguard against deterioration or abrasion.

UV-curable resins are solvent “free”and produce no volatile organic compounds (VOCs) in its low-energy processing, which adds to its environmental friendliness. Industrial sectors like medical, electronics, aerospace, automotive, signage, and packaging, among others, make use of UV curable resins to provide strong adhesion in a reduced timeframe while complying with stringent industry quality requirements. The curing process is dependably consistent for those industries.

UV Curable Resins: How They Work

UV curing goes by numerous names, including UV coating, UV drying, and UV bonding. Regardless of the term, the method uses a UV, LED light or EB source to rapidly harden exposed resins. The process begins with a chemical reaction in the photoinitiator of the liquid resin that allows individual oligomers and monomers to form a complex polymer chain as part of a photopolymerization reaction, which is what solidifies the resin into a solid. Using this chemical reaction, you can paint, dry, or bond materials simply by curing the resin.

After applying the resin to the desired surface, one can choose: high-pressure mercury lamps, UV-LED lamps or Electron Beam (EB). Each process is useful and has its own energy and handling requirements. The high-pressure mercury lamp has multiple emission wavelengths, which help the resin cure optimally. However, this lamp also gets hot quickly and has a short life span.

The UV-LED lamp functions with higher levels of energy efficiency, but it will require more time to cure the resin because it utilizes only one emission wavelength. With the help of UV lamps, jobs can cure in as little as a second to a half hour. If you use natural sunlight instead, curing can take anywhere from several to 24 hours.

Electron Beam curing by delivering energy directly to the formulation in the form of energetic electrons. EB has advantages over UV and LED because the formulations are very similar, but no photoinitiator is required. In addition, the energy can go deeper into the film and is not affected by the color of the UV cure resin or the substrate, which can cause the UV energy to reflect off. The complexity and cost of EB curing has been a deterrent, even with the smaller more cost efficient units currently available.

Acrylic Resins vs. Epoxy Resins

UV curable formulations are based on two different functional groups: acrylate and epoxy. At Toagosei America, we supply both types of monomers to produce UV curable formulations. Our company offers Aronix®, which is composed of special acrylic monomers and oligomers, and Aron Oxetane®, or oxetane monomers for epoxy resins. Both types utilize UV and EB for curing, but each has its own properties and special features.

Acrylic Resin

Acrylate functionality is the main component in acrylic resin, which is cured by a process called radical polymerization. When UV light irradiates acrylic resin, the ensuing chemical reaction generates “free” radicals in the liquid resin. The process of radical polymerization can result in high amounts of volumetric shrinkage after curing occurs, by as much as 7% to 15%.

Exposure to oxygen, or oxygen inhibition, can slow or even halt the acrylic resin’s curing. Once the UV irradiation has paused, or stopped, the curing process will not proceed, even if placed back under the UV lamp. Acrylic resin formulations are the largest percentage of UV cured formulations due to the abundance of low priced monomers and photoinitiators.

Epoxy Resin

Unlike acrylic resins, epoxy resins use epoxide functional groups as its main component, and the photoinitiators create cations which cause the epoxide ring to open. The initial part of the reaction is initiated by UV light, but the propagation portion is driven thermally. The process, called cationic polymerization, has a smaller range of shrinkage during curing, only 1-4%, as compared to acrylate formulations. Oxygen does not interfere with the cure of epoxy based formulation, and the UV curing can be paused and resumed, unlike with acrylate alternatives. Applying heat to the resin will accelerate the curing process. Compared to acrylate based formulations, epoxy formulations have a higher heat and chemical resistance, and epoxy formulations offer excellent adhesion to difficult substrates. However, Formulators have a smaller choice of monomers and cationic initiators and the overall cost can be more expensive.

UV Curable Applications

A highly versatile material, UV curable formulations have a variety of uses. As coatings, they provide added protection for delicate internal electronic components and have applications in coatings, encapsulation, and potting tasks. Their bonding capabilities are also ideal for assembly, sealing, and gasketing. You will often find UV curable resins in the following:

  • 3D printing
  • Digital camera or automotive displays and components
  • Medical instruments
  • Packaging
  • Printed circuit boards (PCBs)
  • Scratch-resistant metal, plastic, wood, or concrete coatings
  • Semiconductors
  • Signage and graphics
  • Smart technology like phones and watches, and other consumer electronics

UV Curable Resins From Toagosei America

Acrylic and epoxy UV curable resins can help you finish and protect your project with fast and dependable results. Toagosei America specializes in unique, functional adhesive and chemical technologies designed to comply with all manufacturing specifications and requirements. As the American branch of the Japan-based Toagosei Group, we are backed by over 70 years of experience as worldwide manufacturers of high-performance chemical and adhesive products and resins.

Since 1994, our Ohio facility has specialized in adhesive advancements, with in-house research and development specialists as well as quality inspections as an ISO 9001- and 14001-certified company.

Toagosei America offers the following UV curable solutions:

To learn more about our UV curable products and their technical product attributes, download our catalog or contact one of our representatives today for prompt, comprehensive information.