6.2.3 Light Cure Adhesives

Light curing adhesives cure when exposed to UV radiation from a light source. There are several light cure product families, including acrylates, CAs, silicones, epoxies and anaerobics; however, the most predominant technology is light cure acrylate. For many of the product families, light curing alleviates some of their disadvantages, such as long cure times, process challenges or depth of cure challenges. For example, light cure CAs have a dual-cure mechanism using both UV/visible light as well as the traditional surface moisture cure (see Section 6.2.1 for more details). This mechanism helps to cure CAs in applications where a large cure through gap is present, with the surface moisture cure mechanism allowing for a full cure in areas not exposed to light. Additionally, light cure adhesives reduce blooming, which can be an issue with some standard grade CA products, particularly when bonding plastics.

Table 24 Summary of light cure technology benefits
Technology Key Benefit Secondary Benefit
Light cure silicone Fast cure Low temperature flexibility, high moisture resistance
Light cure anaerobic Faster cure over traditional anaerobics, higher depth of cure Dual cure in shadowed areas, better cure on inactive substrates
Light cure epoxy On demand curing without heat 1C product
Light cure cyanoacrylate Instantaneous curing No blooming, shadow cure
Light cure acrylates Very fast cure 1C, solvent free

Light curing acrylic adhesives are supplied as 1C, solvent-free liquids with viscosities ranging from 50 mPa.s to thixotropic gels. The cure times of light curing acrylic adhesives depend on many parameters; however, cure times of 2 to 60 seconds are typical and cure depths up to a maximum of 12.7 mm (0.5 in) are possible.

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