Ultraviolet radiation cured adhesives

While the overall rate of increase of adhesive consumption since 1950 has been high, the growth of certain types of products has been especially dramatic. Pressure sensitive and hot melt formulations have been very rapid gainers and anaerobic adhesives too have been strong performers in recent years. Specialty adhesives, including cyanoacrylates (the so-called instant glues) and ultraviolet radiation cured products have also been favorably received. 

The main sources of energy for curing epoxy adhesives by radiation are electron beam (EB) and ultraviolet light (uv). Both provide instantaneous curing of resins that polymerize from a liquid to a solid when irradiated. The uv systems account for approximately 85 percent of the market for radiant cured adhesives, EB systems account for about 10 percent, and the remainder are chiefly adhesives that can cure by exposure to both visible and infrared light. 

Sealants durability resistance to heat cold water, ozone and ultraviolet radiation adhesion to a variety of substrates high recovery colour stability glazing sealants construction sealants (neutral cure systems) sanitary sealants... 

Another possibility of decomposing a C=C-double bond is supplying energy. Radiation contains energy in different forms the heat radiation of a heater or an electric light bulb is known as well as the radiation of an X-ray tube able to penetrate body tissue. Particularly suitable for curing, thus the polymerization of the C=C-monomers, is ultraviolet radiation (UV-radiation), known as a part of solar radiation. If these ultraviolet rays meet with the adhesive monomers to which so-called photoinitiators are added, the double bonds included in the monomers will be decomposed and polymerization proceeds in a way similar to that described in Section 4.3. 

One of the newer developments in adhesives is the growing use of ultraviolet light or electron beam radiation to cure adhesives. Adhesives designed for UV- or E-beam curing are usually pressure sensitive or hot-melt systems based on acrylates, functional rubbers, or epoxidized rubbers, and use special UV or EB lamps to provide the cure. These systems can provide greatiy improved heat resistance compared to hot melts, and avoid the soivent emission problems of some of the solvent-based systems with which they compete. 

Dimethacrylates form highly cross-linked and, therefore, brittle polymers. To overcome brittleness, manufacturers often blend dimethacrylates with polyurethanes or other polymers such as low-molecular-weight vinyl-terminated butadiene-acrylonitrile copolymers and chlorosulfonated polyethylene. The modified dimethacrylate systems provide tough adhesives with excellent properties. These can be formulated as two-component adhesives, the catalyst component being added just prior to use or applied separately to the surface to be bonded. One-component systems also have been formulated which can be conveniently cured by ultraviolet radiation. 

The papers presented in the following chapters represent advances in pressure sensitive adhesives (ultraviolet light activated acrylate monomer - low Tg polyether formulations) photoinitiated cationic polymerization (light activated aryliodonium and arylsulfonium salts of lewis acids in epoxy resin formulations) polymer and formulation design criteria for radiation curable adhesives radiation curable composites (dynamic thermal analysis characterization of electron beam cured... 

Two-part systems Single-part, cured via catalyst or hardener Moisture-curing adhesives Radiation (hght, ultraviolet, election heam, etc.)-curing adhesives Adhesives catalyzed hy the substrate... 

Radiation curing is defined as the polymerization (crosslinking) of a coating, ink, or adhesive directly on a substrate (such as paper, metal, or plastic) via interaction with incident radiation. Although a number of radiation forms have been used, current technology is dominated by ultraviolet (UV) and electron beam (EB) curing. Polymerization usually takes place by a free radical mechanism cationic polymerization is also practiced although limited to UV initiation,... 

Nearly 42% of the demand for all adhesives comes from the packaging sector. Radiation-curable adhesives are used primarily for packaging, with paper and paperboard the dominant materials used in the packaging. Radiation-curable adhesives can be used on glass, metal and some plastic materials. Other applications for radiation-curable adhesives are in healthcare, electronics, communications, pressure-sensitive tape and consumer applications. Ultraviolet (UV)-curable adhesives are best suited to small-scale applications, while electron beam (EB)-curable adhesives are more appropriate in high-volume applications (an EB system has a higher installation cost). One additional characteristic of EB-curable adhesives is that they can cure the area between two substrates. UV light-cured adhesives can also be applied on heat-sensitive substrates and are not affected by ambient temperature or humidity. 

The increased use of ultraviolet radiation to cure adhesives in assemblies containing UV transparent materials such as glass or plastic also seems assured. These adhesives rapidly develop high bond strength, and consume very little energy. 

Epoxy adhesives that cure via radiation (ultraviolet light or electron beam energy)... 

Doyle, Daryl J. (1989). A Review of Ultraviolet (UV) Radiation as an Adhesive Curing Agent. Society of Manufacturing Engineers Technical Paper AD89-534, Adhesives 89, September 12-14, 1989, Atlanta, Georgia. 

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