Radiation cure silicones

Radiation curing silicones, Goldschmidt Informiert 65, January 1987. 

Radiation-curable epoxy acrylates, 10 450 Radiation cures, silicone network preparation via, 22 567-569 Radiation curing coatings, 7 133-135 of printing inks, 14 314 Radiation damage, ion implantation and, 14 435-436 Radiation drying coatings, 7 29-30 Radiation effects... 

Gordon GV, Moore PA, Popa PJ, et al. Radiation cured silicone release coatings sticking lightly. In Proceedings of the RadTech America. Baltimore 2000 994—1006. 

Systems using either gamma radiation from cobalt 60 or electron beams have been used for vulcanization. The electron beam method has been used for curing silicone rubbers. 

A very elegant technology for curing silicone has been developed during the same period. Because silicone polymers themselves are transparent to UV light, radiation curing is particularly suitable for silicone polymers. 

Typical physical properties obtainable with UV cured silicones are provided In Table I. Incorporation of reactive unsaturation into the silicone polymer backbone In combination with a photosensitization system provided the photocure capability. Properties of a standard heat-cured encapsulant developed for use on semiconductor devices, Dow Corning HIPEC R-6103, are provided for comparative purposes. Clearly, introduction of a photocrosslinking mechanism into a siloxane type composition has afforded the desired result. The one-part, solventless, UV curable silicone composition cured rapidly upon exposure to UV radiation, providing a cured composition which has retained the typical properties that make silicones so attractive for protection of semiconductor devices. 

Pressure-sensitive adhesives are the essential components of adhesive tapes and labels. They are polymers with permanent tack, usually applied on substrates (plastic/metal films, siliconized papers). To enhance their tack, compounds with high inherent tack are added, for example, resins, plasticizers. Pressure-sensitive adhesives reach their adhesion on the material to be bonded by contact pressure, from which the term pressure-sensitive adhesive (PSA) derives. Apart from electron radiation, also UV-radiation curing described in Section 4.3.2 is applied in adhesive tape manufacturing. The monomer molecules to be polymerized are applied, in liquid form, to the substrates to be coated by rolling and are continuously cured to a polymer layer within seconds under a UV-radiation source. Depending on their composition, predetermined adhesion values can be adjusted. The adhesive tapes can be subsumed under the systems shown in Figure 5.4 ... 

Silicone rubber has a three-dimensional network structure caused by cross-linking of polydimethyl siloxane chains. Three reaction types are predominantly employed for the formation of silicone networks (155) peroxide-induced free-radical processes, hydrosilylation addition cure, and condensation cure. Silicones have also been cross-linked using radiation to produce free radicals or to induce photoinitiated reactions. 

Radiation cure of methylvinyl silicone mbber results in a random cross-linking process with no differentiation between methyl and vinyl groups... 

Among the most successful of the new radiation-curable silicone coating systems are compositions Incorporating cycloaliphatic epoxyfunctional silicone polymers with compatible iodonlum salt photocatalysts (1 - S ) The syntheses, structures, UV cure response, and other properties of these materials and some of their derivatives and monomeric homologs are discussed In the balance of this chapter. Their specific application for release coatings has been described In great detail elsewhere (5.6 > and Is not the subject of this paper. 

While most of these films are clearly low-modulus materials, they possess properties useful for such radiation-cure coating applications as conformal coatings, electronic encapsulent gels, or fiber optic coatings, particularly where such applications demand silicones broad operational temperature range,... 

Uses Filler for polyolefins, silicone rubber, radiation-cured systems, road marking paints... 

Chem. Descrip. Silicone acrylate oligomer Uses Silicone-acrylic for radiation-cured coatings and inks Features Hard films exc. adhesion and weatherability Regulatory EINECS, CEPA listed... 

Chem. Descrip. Methaciyloxypropyl en blocked silicone polymer Uses Crosslinking agent for heat- or radiation-cure coatings, synthesis of silicone/organic copolymers... 

Uses Silicone for prod, of silicone/org. copolymers, heat- or radiation-cured coatings... 

Uses Conditioner alkyd resin comonomer mfg. of varnishes, synthetic drying oils, urethane foams and coatings, silicone lube oils, lactone plasticizers, textile finishes, surfactants, epoxidation products crosslinking agentfor PU reactive diluent for radiation-cured inks, lacquers heat costabilizer for PVC in food-pkg. adhesives in food-contact coatings... 

Narisawa, M., Idesaki, A., Kitano, S., Okamura, K., Sugimoto, M., Seguchi, T., Itoh, M., Use of blended precursors of poly(vinylsilane) in polycarbosilane for silicon carbide fiber synthesis with radiation curing. Journal of the American Ceramic Society 1999,82(4), 1045-1051. 

Wach, R. A., Sugimoto, M., Yoshikawa, M., Formation of silicone carbide membrane by radiation curing of polycarbosilane and polyvinylsilane and its gas separation up to 250°C. Journal of the American Ceramic Society 2007, 90(1), 275-278. 

S. Kamimura, K. Watanabe, N. Kasai, T. Seguchl and K. Okamura, Silicon nitride fiber synthesis from polycarbosilane fiber by radiation curing and pyrolysis under ammonia, Ceram. Transactions, 58, 281-286 (1995). 

---