Radiation-curable adhesives applications

One key consideration in developing radiation curable adhesive systems is the thermal stability and volatility of any photoinitiators used. These chemicals are designed for liquid systems where these issues do not arise. Few of the commercial photoinitiators have adequate thermal stability at the highest hot melt temperatures (180-200°C) and many are too volatile. Reduced application temperatures and special antioxidant packages are often required. 

Furthermore, the understanding of how and which materials to assemble to make an adhesive that will cure to suit a given application is currently limited to a relatively narrow circle of practitioners. There have been just enough radiation curable adhesives with inadequate performance marketed prematurely to make some manufacturers assume that such adhesives won t work properly. Availability of worthwhile products is limited, although their number is constantly growing. 

Table Applications Summary for Radiation Curable Adhesives...

Other properties of radiation curable adhesives are reported by the manufacturer according to the application. If unexposed to light and heat, they will remain open and nonclogging. The user who is unfamiliar with formulation techniques should be sure to request information from the supplier on suitable thinner and cleanup solvents. Extension with fillers and additives should also not be attempted without understanding of these systems. 

Wider application of radiation-curable adhesives in flexible packaging Reduced cost of adhesives Improved adhesion properties Reduced odour Reworkable adhesives Adhesives for PET. 

Overview of radiation-curable adhesives in packaging applications... 

The demand for radiation-cured adhesives is largely attributed to the requirement for specific adhesive properties essential in certain end-use applications. Some of the properties being focused on by radiation-curable adhesives manufacturers are ... 

Oligomers can be of several types based on the base chemistry. Some of the important oligomers that find applications in radiation curable adhesives include epor acrylates, polyesters and polyurethanes. All of these oligomers differ in the way they link at a molecular level upon curing. 

It is expected that radiation-curable adhesives will emerge as one of the most cost effective and technically superior alternatives for most packaging applications in the near future. 

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. 

Summary This chapter deals with the various end-use applications for which radiation-curable adhesives are used. Successful application of adhesive requires the input of multiple decision makers such as product development engineers, adhesive suppliers, application equipment vendors and end product customers. Nearly 42% of the application of all adhesives comes from the packaging sector. 

UV-curable adhesives, and, in general, radiation-curable adhesives, use UV light or other radiation sources to initiate curing. A permanent bond forms without application of heat by means of free-radical chemistry. The advantages of UV curing include lower application temperature (120—140° C),... 

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