Electron beam curing Cross-linking

Because of the precise control of the degree of cross-linking attainable by the electron beam process, it is well suited for the production of PSAs. Recent developments in EB design, particularly lower voltage, and materials developments have made electron beam curing of pressure-sensitive adhesives affordable, practical, and possible. ... 

The electron beam curing of coatings has for some time attracted a great deal of attention since It Is claimed that coatings can be fully cured In a fraction of a — second. The coatings are primarily based on the cross-linking of acrylic or epoxy resins In a polyurethane or polyester base (l.e., modified paints). 

An electron beam curing process can reduce the oxygen content by an oxygen free cross-linking process [32]. The fiber, composed of fine fi-SiC crystallites... 

Radiation cross-linking of polyethylene requires considerably less overall energy and less space, and is faster, more efficient, and environmentally more acceptable. Chemically cross-linked PE contains chemicals, which are by-products of the curing system. These often have adverse effects on the dielectric properties and, in some cases, are simply not acceptable. The disadvantage of electron beam cross-linking is a more or less nonuniform dose distribution. This can happen particularly in thicker objects due to intrinsic dose-depth profiles of electron beams. Another problem can be a nonuniformity of rotation of cylindrical objects as they traverse a scanned electron beam. However, the mechanical properties often depend on the mean cross-link density. ... 

The prevulcanization of natural rubber in latex form has also been a subject of much investigation. The cross-linking mechanism is not yet fully understood, but the water apparently plays a major role in it. Irradiation results in the cross-linking of the rubber molecules and in coarsening of the latex particles. A process of cross-linking of natural rubber latex has been developed to the point that it can be used for an industrial-scale application. The irradiation is performed in aqueous media by electron beam without a prorad (sensitizer) at a dose of 200 kGy (20 Mrad) or in the presence of n-butyl acrylate at considerably lower doses, typically 15 kGy. The cross-linked film exhibits physical properties comparable to those obtained from sulfur cured (vulcanized) film. As an alternative, the addition of a variety of chloroal-kanes makes it possible to achieve a maximum tensile strength with radiation doses of less than 5 Mrad (50 kGy). ... 

Thermosetting composites are cured at either ambient or elevated temperatures to obtain a hard solid by cross-linking. The use of radiation cross-linking decreases the cure time considerably. In particular, an electron beam has been used successfully in many instances. Eor example, glass-fiber-reinforced composites cured by electron beam have been used for the production of cladding panels. ... 

A process of cross-linking of natural rubber latex has been developed to where it should be soon ready for an industrial-scale process.149 The irradiation is performed in aqueous media by electron beam without a prorad ( sensitizer ) at a dose of 200 kGy (20 Mrad) or, in the presence of n-butyl acrylate at considerably lower doses, typically 15 kGy. The cross-linked film exhibits physical properties comparable to those obtained from sulfur-cured (vulcanized) film. 

Electron beam (EB) cure — A process using high energy (accelerated) electrons to promote reactions in a polymeric material (cross-linking, polymerization). The reaction is instantaneous. The voltage range used in this process is typically from hundreds of kilovolts to several megavolts. 

Examples of such photochemical acid generators are shown in Chart 3.2. These onium salts, which are cationic photoinitiators originally developed for curing of epoxy resins (i09), can be used to formulate cross-linking negative resist materials (JOS), are very sensitive to electron beam and X-ray (JOS, 107, 108) radiation, and can be sensitized to longer wavelength radiation (JOS, 110, 111). 

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