Epoxy-anhydride coatings

Foix D, Rodriguez MT, Ferrando F, Ramis X, Serra A (2012) Combined use of sepiolite and a hyperbranched polyester in the modification of epoxy/anhydride coatings a study of the curing process and the final properties. Prog Org Coat 75 364-372... 

Anhydrides. Polyanhydrides and not monoanhydrides must be used to cure epoxy surface coatings. They are used in powder form for powder coatings and in solution for can coatings both forms are hot curing. The films have a good acid resistance, and do not impart an undesirable taste to foods. 

The main polymer use in chip resistors relates to the encapsulation material which is frequently PA but may be Novolac epoxy or epoxy resin. Silicone rubber encapsulation, which provides a cushioning layer which isolates the resistive element from external stresses, and polymerised moisture protection layers are two other uses of polymers in resistors. Encapsulated resistor capacitor networks utilise epoxy/anhydride conformal body material. Conformal implies a coating of uniform thickness as would be obtained by a dipping process, for example. 

Epoxy resin coatings can be divided into two distinct types (a) ambient cured and (b) heat cured. The ambient-cured systems are crosslinked through the oxirane ring by using polyamines, amine adducts, polyamides, polythiols and catalytic cures, while the heat-cured systems are crosslinked through reactions of the hydroxyl groups, or in some cases a combintion of the epoxy and hydroxyl functionality, by using anhydrides and polycarboxylic acids as well as MF, UF and phenol-formaldehyde resins. 

Epoxy Resins. Epoxy resins (qv) are used to cross-link other resins with amine, hydroxyl, and carboxyHc acid (or anhydride) groups. The epoxy group, properly called an oxkane, is a cycHc three-membered ether group. By far the most widely used epoxy resins in coatings are bisphenol A (BPA) (4,4 -(l-methylethyHdene)bisphenol) [80-05-7] epoxy resins. 

For this use, the preferred powders are based on acrylic, epoxy or polyester and epoxy resins. For best colour, epoxy resins are crosslinked with anhydrides of dicarboxylic acids in the straight epoxy coatings, or with saturated polyesters of high acid content in the epoxy-polyester type. Acrylics contain epoxide rings via, for example, glycidyl methacrylate (CH2=C(CH3) —CO—O—CHj—CH —CH2), and these groups crosslink... 

Silanes used for treatment dimethyldiethoxy silane, 3-(methacryloxy) propyltrimethoxy silane, vinyl triethoxy silane, amino silane. Silane coating was estimated to be 0.2 wt%. Treatment with epoxy silane has been used followed by PS-maleic anhydride grafting through amine spacer. 

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