UV Curing Adhesives

UV curing adhesives use ultraviolet (UV) light or other radiation sources to initiate curing and form a permanent bond without heating. They are compatible with substrates made of ceramic, composite material, concrete, fabric, glass, metal, paper, plastic, rubber, or wood. UV curing adhesives use various chemical systems, most of which are polymer-based. Choices include acrylic, epoxy (EP) polybutadiene, polyester, silicone, styrene copolymer, and vinyl. Some UV curing adhesives contain additional modifiers such as fillers, pigments, or chopped fiber reinforcements. Others contain solvent-based adhesive resins which use a volatile organic compound (VOC) to thin or alter viscosity. Typically, solvent-based UV curing adhesives pose greater environmental or regulatory issues.  

Selecting UV curing adhesives requires an analysis of processing and physical properties, thermal properties, and mechanical properties. Processing and physical properties include gap fill, the spacing or gap between the substrate and adhesive or sealant; and viscosity, a measurement of a fluid’s resistance to flow. Use temperature, thermal conductivity, and coefficient of thermal expansion (CTE) are important thermal properties to consider. Use temperature is the range of temperatures to which products can be exposed without the degradation of structural or other required end-use properties. Thermal conductivity is the linear heat transfer per unit area through a material for a given applied temperature gradient.   CFE is the amount of linear expansion or shrinkage that occurs in UV curing adhesives with a change in temperature. 

UV curing adhesives also carry specifications for electrical and optical properties. These include electrical conductivity, dielectric strength, dielectric constant or relative permittivity, index of refraction, and transmission. The inverse of conductivity, resistivity is the longitudinal electrical resistance (ohm-cm) of a uniform rod of unit length and unit cross-sectional area. Dielectric strength is the maximum voltage field that UV curing adhesives can withstand before electrical breakdown occurs. Dielectric constant is the relative permittivity of a material compared to a vacuum or free space. The index of refraction is a measure of the speed of light in a material. This is the amount of light transmitted through a material. 

With UV curing adhesives, setting or curing time is the time required for fully curing or setting a bond system.  In thermosetting, hydraulically or other chemically-setting systems, the time will vary depending on the actual curing temperature. In UV curing adhesives, however, cure time can be quite rapid. Some styles of UV curing adhesives bond instantly upon the application of UV light. Others, which are more common, begin tacking when contacted by UV, but still require a given length of time to fully set. Longer cure times will be required for lower-curing temperatures.

• UV Curing Adhesives and Potting Compounds
  Recent advancements in ultraviolet curing have given engineers a new opportunity when choosing adhesives, potting compounds, coatings, and sealants. Until now, most of these systems were either...
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• UV-Cure Adhesives 101
  UV-curing adhesives can help get manufacturers out of sticky situations. A technician uses a UV curable adhesive for perimeter bonding an optic component to a metallic part. Organic adhesives usually...
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• Guidelines for Bonding Plastics
  The key to quick and permanent assembly is matching adhesives and plastics. Plasticized PVC anesthesia masks are bonded with light-curing adhesives, shown here entering a cure chamber. A variety of...
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Part Numbers for UV Curing Adhesives