Epoxy resins curing polymerization

A waterborne system for container coatings was developed based on a graft copolymerization of an advanced epoxy resin and an acryHc (52). The acryhc-vinyl monomers are grafted onto preformed epoxy resins in the presence of a free-radical initiator grafting occurs mainly at the methylene group of the aHphatic backbone on the epoxy resin. The polymeric product is a mixture of methacrylic acid—styrene copolymer, soHd epoxy resin, and graft copolymer of the unsaturated monomers onto the epoxy resin backbone. It is dispersible in water upon neutralization with an amine before cure with an amino—formaldehyde resin. 

Uses Cafalysf for esferificafion and fransesferificafion reactions cafalysf for cure of epoxy resins in polymeric coatings for food pkg. 

Acceleration of epoxy cures by carboxylic acids is frequently accomplished by addition of a base catalyst. Cure of epoxy resins by polymeric fatty acids (molecular weight 500-900) has been accelerated by the formation of fatty acid/melamine soaps (53). DGEBA-resin-based adhesives have also been cured with piperazine/polycarboxylic acid (e.g., succinic acid) salts (54). These adhesives showed rapid heat cures (23 min at 120°C) and good room temperature latency (shelf life of 60-65 days). The rate of cure in these adhesives was faster than comparable adhesives having dicy... 

Wang, M.H., Yu, Y.F., Wu, X.G., and Li, S.J. (2004) Polymerization induced phase separation in poly(ether imide)-modified epoxy resin cured with imidazole. Polymer, 45 (4), 1253-1259. 

A second type of uv curing chemistry is used, employing cationic curing as opposed to free-radical polymerization. This technology uses vinyl ethers and epoxy resins for the oligomers, reactive resins, and monomers. The initiators form Lewis acids upon absorption of the uv energy and the acid causes cationic polymerization. Although this chemistry has improved adhesion and flexibility and offers lower viscosity compared to the typical acrylate system, the cationic chemistry is very sensitive to humidity conditions and amine contamination. Both chemistries are used commercially. 

With the exception of epoxy resins, when a resin is fully polymerized it loses any irritant properties. However, associated materials, e.g. glass fibre used as a filler, or the dust from plywood or veneers, may promote initation. Partially-cured resins will retain some uritant properties. Traces of cutaneous or respiratory sensitizers liberated, e.g. by heating or machinery, may be problematic. 

Janke, C.J., Dorsey, G.F., Havens, S.J. and Lopata, V.J., Electron beam curing of epoxy resins by cationie polymerization. 4Jsl International SAMPE Symposium, 196, 1996. 

The first moment of the distribution is Pt0T the total, cumulative molar concentration of polymeric material. As the molecular weight of polymeric species increases, branching and crosslinking reactions yield a thermoset resin. Chromatography analysis of epoxy resin extracts confirms the expected population density distribution described by Equation 4, as is shown in Figure 2. Formulations and cure cycles appear in Table II. 

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