Crosslinking epoxy/acid

However, in unpublished works in the author s laboratory the use of polyamic acids to cure epoxy resulted in no decrease in dielectric constants of the epoxies examined. This lack of improvement was attributed to the presence of a large number of unreacted carboxyl groups and the presence of large quantities of hydroxyl groups from the incompletely crosslinked epoxy network. 

Many cyclic acid anhydrides are used industrially for crosslinking epoxy resins. These are mono-and polyanhydrides. Some typical, conunercially used anhydrides are shown. 

Epoxy resins Crosslinkers, amines, acids Industrial coatings, anticorrosive coatings, industrial maintenance coatings... 

The analogous reaction between castor (or lesquerella) oil and sebacic acid also forms an aliphatic polyester. Unlike the epoxy-acid reaction, water is formed as a by-product, which must be removed from the reaction medium in order to obtain complete reaction and a void-free material. The reaction may be carried out with deliberate stoichiometric imbalance to form a high molecular weight hydroxy endcapped prepolymer, which may be thoroughly dried, and then crosslinked with a diisocyanate, which form urethane crosslinks without the release of water. Of course, hydroxy functionalized oils can also be reacted from the start with a diisocyanate, forming a complete polyurethane network,... 

Epoxy amine adduct Crosslinker Organic acid Organic solvent Deionized water... 

Cycloahphatic diamines react with dicarboxyUc acids or their chlorides, dianhydrides, diisocyanates and di- (or poly-)epoxides as comonomers to form high molecular weight polyamides, polyimides, polyureas, and epoxies. Polymer property dependence on diamine stmcture is greater in the linear amorphous thermoplastic polyamides and elastomeric polyureas than in the highly crosslinked thermo set epoxies (2—4). 

The term epoxy is familiar to nonchemists because of the widespread use of epoxy glues and resins. These are crosslinked polyether thermoplastics made from a liquid resin which is typically a mixture of bisphenol A diglycidyl ether (70) and a polymer (71 Scheme 86). The liquid resin is cured or hardened to the final resin by mixing with a crosslinking reagent, which can be an acid, a di- or poly-alcohol, or a di- or poly-amine (Scheme 86). 

The UV cure system contains an epoxy or a vinyl ether functionalized PDMS polymer and a photo catalyst [36]. This latter, a diaryliodonium salt is photolyti-cally decomposed to form an active acid that polymerizes the epoxy or vinyl ether groups and crosslinks the network. 

For resistance to acid conditions alone, traditional filled and unfilled bituminous solutions (which have economic advantages), chlorinated rubber and shellac have been used. Crosslinking coatings, e.g. amine-cured epoxy resins, often blended with coal-tar which develops resistance to oils and solvents, have obvious advantages on chemical plant. 

This provides excellent adhesion to the metal. The PVB will crosslink in the presence of the acid with phenolic resin, and epoxy or epoxy ester resin... 

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... 

Epoxy (Anhydride-Cured) Epoxy resins may be crosslinked with various anhydrides by using a tertiary amine accelerator and heat. These cured polymers generally have good chemical resistance especially to acids. 

Microgels have been prepared from epoxy resins which were intramolecular-ly crosslinked by a polyalkylene polyamine/polycarboxylic acid for flexible, corrosion resistant coatings [354]. 

In alkaline and acid solutions, thermosets containing ester groups are degrated mainly due to the hydrolysis of the esters (1-6) But in case of the resin crosslinked by ester bonds such as some epoxy resins (7-9). corrosion behavior is though to be different from that of the resin which has ester bonds in the main chain. 

Nylons 6/6 and 6 comprise more than 90% of the polyamide market. The two have similar properties but nylon 6 has a lower Tm (223°C). Small amounts of nylons 6/9, 6/10, 6/12, 11, 12, 12/12, and 4/6 are produced as specialty materials. Those with more methylene groups than nylons 6/6 and 6 have better moisture resistance, dimensional stability, and electrical properties, but the degree of crystallinity, Tm, and mechanical properties are lower. Specialty nylons made from dimerized fatty acids find applications as hot-melt adhesives, crosslinking agents for epoxy resins, and thermographic inks. 

Crosslinking of epoxy plastics through the hydroxyl groups of the repeat unit is used for prepolymers with low epoxide group contents. The most common curing agent is phthalic anhydride although other acid anhydrides such as tetrahydrophthalic, nadic methyl, and chloroendic anhydrides are used in specialty applications ... 

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