Radiation-curing monomers and resins

In-situ Polymerisation with Radiation Curing Monomers and Resins... 

As an alternative to PEG treatment of waterlogged wood, attempts have been made to use a radiation curing method involving a range of monomers and resins. The aim of such treatments is to reduce treatment times and achieve a more stable artefact. Styrene, vinyl acetate, acrylonitrile, acrylates and methacrylates are the most studied monomers in the treatment of waterlogged archaeological wood. The most widely used of these monomers is the water-soluble vinylpyrrolidone and methacrylamide and the non-water soluble chemicals such as n-butyl methacrylate monomer or unsaturated polyester resin. 

The aim of this section is to emphasize the specific features of the radiation-curing method. Waterlogged wood samples were treated with the monomers and resins described previously. A quite sound wood and a very degraded one were tested. Assessment of the results was based on their behavior during irradiation, their surface appearance, and their dimensional changes. 

For the radiation rapid cure experiments, appropriate resin mixtures containing oligomers, monomers, flow additives and sensitisers (UV) were applied to the substrate as a thin coating, the material placed on a conveyor belt and then exposed to the UV and EB sources. The time taken to observe cure for each of the samples was then measured on a relative basis. The UV system used was a Primarc Minicure unit with lamps of 200W per inch. Two EB facilities were utilised namely a 500KeV Nissin machine and a 175KeV ESI unit. 

Radiation curing adhesives are generally applied as solvent-free liquids. High-solids EB and uv curing liquid adhesives have been formulated from a variety of resins and elastomers. They include epoxy acrylates, epoxies, other acrylates, polyesters, blends of acrylate monomers with elastomers, and other compositions. 

Monomers are primarily used to lower the viscosity of the uncured material to facilitate application. The monomer must be matched with the resin to give the desired set of properties with respect to adhesion to the substrate and bulk properties such as flexibility, stiffness, cure behavior, and durability. Early radiation curable monomers had problems associated with toxicity and skin sensitivity newly developed monomers have been significantly improved in this respect. 

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 ... 

Gamma irradiation curing of epoxy resins for structural adhesives — Radiation cure polymerization of commercial diglycidyl ether of bisphenol F epoxy resin has been achieved using Co-60 irradiation source, compounding the monomer with and onium salt catalyst [9],... 

The polymerization kinetics were studied via time-conversion relationships at different dose rates (Figures 6-9). The radiation curing was carried out at room temperature in closed aluminum capsules. Percent monomer conversion was determined gravimetrically for N-vinylpyrrolidone. Evaporation was accomplished under vacuum in a ventilated oven at 50 °C until the weight was constant. For butyl methacrylate and polyester resins, the residual monomer content was determined by gas chromatographic analysis after immersion of the cured products in acetone. 

Acrylic adhesives first appeared about 1937 the acrylic resins may be considered as belonging to the vinyl family [1, p. 305], Today, acrylic adhesives appear in many forms as both pressure-sensitive and non-pressure sensitive formulations in organic solvent and emulsion forms as monomer and polymer cements as anaerobics as cyanoacrylates as so-called reactive or honeymoon two-part systems and as radiation curing formulations. Commercial production of acrylic polymers began in the late 1920s, but it was not until 1958 that the first aerylie sealant was developed [10, p. 226]. The solvent-based acrylic sealants were first introdueed to the eonstruction industry in about 1960 ... 

Uses Monomer for prod, of thermosetting resins for protective coatings or top coatings for leather, metal, and other substrates crosslinking agent in radiation-cured systems, for photoresists, latex, sol n. coatings Features Bifunctional self-crosslinking Cylink NBMA [Cytec Ind.)... 

Chem. Descrip. Hydroxyethyl acrylate CAS 818-61-1 EINECS/ELINCS 212-454-9 Uses Monomer for prod, of resins used in high performance coatings, pressure-sensitive adhesives and coatings for plastics and flexible substrates, radiation-cured resins, emulsion polymers and additives for personal care prods, and ion exchange resins Features Provides better adhesion, impact resist., flexibility and faster reactivity than methacrylate analogs Properties Colorless clear mobile liq. si. acrylic odor completely misc. with water, common org. soivs. dens. 1.101 g/ml vise. 8 cps (15.5 C) vapor pressure 0.1 mm Hg t.p. -30 C b.p. 192 C flash pt. (PMCC) 101.1 C 97.5% min. assay... 

Chem. Descrip. Hydroxypropyl acrylate CAS 25584-83-2 EINECS/ELINCS 247-118-0 Uses Monomer for prod, of resins used in high performance coatings, heat-cured topcoats, pressure-sensitive adhesives and coatings for plastics and other flexible substrates, radiation-cured resins Features Provides better adhesion, impact resist., flexibility and faster reactivity than methacrylate analogs... 

Chem. Descrip. Polyether triol containing primary hydroxyl groups Uses Flow aid, leveling agent, abrasion resist, aid for radiation-curable monomers, urethane and polyester resins, high-solids coatings, polyester resin synthesis reactive modifier for UV cationic cure systems Features Good compat. with resin systems Properties Lt. yel. clear liq. m.w. 240 sp. gr. 1.1 dens. 9.2 Ib/gal vise. 800-900 cps hyd. no. 680-710 pH 6-8 (2%) 0.5% moisture... 

Chem. Descrip. Etherified acrylated melamine/formaldehyde resin (62-68%) in tripropylene glycol diacrylate Uses Crosslinking agent in radiation-cure applies, such as polyester and epoxy acrylates, unsat. polyesters, aliphatic and aromatic urethane acrylates, and most acrylate monomer diluents imparts hardness and gloss, stain and chem. resist, to coatings, paper coatings Features Cured by free radical polymerization initiated by U V or thermal processing... 

Uses Monomer for creating and modifying polymers, acrylic resins, urethane methacryiates marine antifouling paint resin comonomer reactive comonomer for acryiic and S/B resins rubber modifier binder for textiies/paper adhesives, nonwoven fabrics, enamels, adhesives grafting of textiie fibers scaie inhibitors adhesion promoter for polymers hydrophilic polymers It.-curing polymer systems reactive thinner for radiation curing food-pkg. adhesives, polymers Manuf./Distrib. Acros Org. Aldrich Allchem Ind. Ashland BP Amoco Electron Microscopy Sciences Fluka ICN Biomed. Research Prods. Kessler Lancaster Synthesis Laporte Perf. Chems. Monomer-Polymer Dajac Labs Pfaltz Bauer Rohm Haas Rohm Tech San Esters Scientific Polymer Prods. Sigma TCI Am. Ubichem pic Whyte Chems. Ltd... 

Uses Curing agent reactive diluent monomer (UV EB resin) and modifier for radiation-cured coatings, inks, electronics applies., paints, textile finishes, adhesives, industrial and textile coatings Features Resists UV degradation... 

Uses Flow aid. leveling agent, abrasion resist, aid for radiation-curable monomers, urethane and polyester resins, high-solids coatings, polyester resin synthesis reactive modifier for UV cationic cure systems Trade Names Photonol PHO-7149... 

Solvents can be replaced with reactive diluents like some monomers, as is the practice with unsaturated polyesters and with radiation-curing polymers. Polyfunctional monomers like unsaturated melamine resins are becoming used as diluents for alkyd resins [61]. 

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