Лако-красочные материалы — производство

Type I epoxy systems are aqueous emulsions of liquid epoxy resins (with epoxy equivalent weight ~200). In this type of waterborne epoxies, no external emulsifiers are used, but rather, curing agents (fatty polyamide type) serve as emulsifiers due to their amphiphilic nature. Liquid epoxy resin and curing agent are mixed in calculated quantities just prior […]

Like other resins and coating systems, demand for waterborne epoxy resins has steadily increased over the past several decades. Waterborne epoxy resins and their coatings are commercially available. Water­borne epoxy resin systems can be broadly classified into the following categories, based on the techniques involved in their processing. • Emulsified system — Type I: based […]

In the presence of a suitable catalyst, epoxy groups can undergo self­polymerization to generate a polyether through either a cationic or anionic mechanism. Anionic polymerization occurs in the presence of tertiary amines (Lewis bases) such as tris(dimethylaminomethyl) phenol, benzyldimethylamine or imidazole derivatives, while cationic polymerization can occur in the presence of Lewis acids. Boron trifluoride […]

Both resole and novolac type phenolic resins are used to cure high MW epoxy resins to give a hard and tough film with very good chemical and corrosion resistance. Such systems are generally cured at high temperatures of about 150 to 200 °C. The phenolic hydroxyl groups in both resoles and novolacs can react with […]

Secondary hydroxyl groups of the epoxy resin backbone may be reacted with polyisocyanates, aromatic as well as aliphatic, in two — component ambient curing systems that are commonly known as epoxy-urethane hybrid systems. This type of coating combines advantages of epoxy and polyurethane systems. 2.9.3.3 Carboxylic acids and anhydrides Figure 2.54: Curing of epoxy with […]

Mannich bases are derived by reaction of phenol, formaldehyde and an aliphatic or cycloaliphatic polyamine. These curing agents show enhanced reactivity due to the catalytic effect of phenolic hydroxyl. Phenalkamines are similar products using alkyl phenols (Figure 2.50). Cardanol-based phenalkamines are very popular pro­ducts used in marine and protective coatings. These types of curing agents […]

Amine functional polyamides are prepared by reacting dimer fatty acids with excess equivalents of polyamines. The products are effec­tive epoxy curing agents, with both primary and secondary amines available for curing. Figure 2.49 shows a representative structure, though more than one dimer fatty acid segment is possible based on the ratio of reactants. The spacing […]

The most common aliphatic polyamines belong to the homologous series of diethylene triamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA), which contain both primary and secondary amine groups. Aliphatic polyamines (Figure 2.45) cure epoxy resins at a fast rate and produce a densely cross-linked network with very good chemi- cal resistance. However, they suffer from such […]

Most frequently, for ambient curing systems, aliphatic or cycloa­liphatic polyamines or amine functional polymeric or oligomeric derivatives are the curing agents of choice. Epoxy groups can react with primary and secondary amine groups, respectively forming secondary and tertiary amine groups. The reactivity depends on type of amine. The general order of reactivity of amines is […]

Epoxy resins are thermosetting polymers, and the final properties of the polymer network are largely influenced by proper selection of the curing agent. Cross-linking of epoxy resins may be carried out through epoxide as well as hydroxyl groups. These reactions may be of the ambient curing or thermal curing type. The electron-deficient carbon atom of […]