Amidoamine: Synthesis, disparity in cure with epoxy resins between bulk and solvent systems, and structure–property relationships of its epoxy‐based coatings

Abstract

Amidoamines are widely used as crosslinkers for epoxy resins in protective coatings on metal substrates; however, their cure chemistry is not well elaborated in the technical literature. During cure, the epoxy–amine and epoxy–amide NH reactions could be accompanied by epoxy–hydroxyl etherification, epoxy–epoxy homopolymerization, and reaction between hydroxyls and amide moiety to form in situ ester and amine. To understand the epoxy–amidoamine cure chemistry and correlate it with coating performance properties, amidoamines of known structure are required. Therefore, amidoamines were synthesized by reacting dimer fatty acids with diethylene triamine. When these amidoamines were cured with epoxy resins, discrepancies were observed between systems cured at ambient and thermal conditions. The presence of solvents were seen to greatly affect the rate of epoxy–amidoamine cure at ambient, and before and after vitrification. Near‐IR and mid‐IR spectroscopy studies indicated that side reactions occurred to some extent during cure. No reaction was noted between the amide NH moiety and the epoxide group below 150°C whereas ester formation was noted above 120°C. Solvent‐based clear epoxy–amidoamine coatings formulated at an epoxy:amine equivalent ratio 1.15 passed basic organic coatings evaluation tests. POLYM. ENG. SCI., 59:E69–E81, 2019. © 2018 Society of Plastics Engineers

Recyclable vitrimer epoxy coatings for durable protection

“…Because one of the primary goals of this research was to develop a dynamic (poly)amine curing agent with competitive properties compared to a readily used polyamidoamine hardener (Ancamide 2864), the starting point of this research effort was the selection of appropriate monomers. Generally, polyamidoamines are obtained by reacting a bio-based fatty acid with an amine mixture, 6 whereby good flexibility and hydrophobicity are mainly attributed to the dimer compound. Analogously, when preparing the VU-based curing agent (see Figure 1), the fatty acid derived Priamine 1074 (1) was selected for its hydrophobic nature and mixed with 1,3bis(aminomethyl)cyclohexane (BAC, 2) and 1,4-butanediol diacetoacetate (BDAA, 3).…”

“…For two-component epoxy coatings, the most popular compounds in this regard are (poly)amines and reactive amidoamines, which offer the advantage of flexibility and high hydrophobicity. [5][6][7] Nevertheless, like all covalently cross-linked materials, epoxy resins do not flow and cannot be healed, reshaped or recycled, and are thus discarded after damage or failure. As a result, there has been an increasing interest in the synthesis and application of robust, but responsive hardeners for dynamic polymer networks in recent years in order to (re)use epoxy materials more efficiently.…”

Synthesis and application of thermal latent initiators of epoxy resins: A review

“…When the epoxy resin is mixed with a curing agent, under proper curing conditions, curing reactions occur forming a three-dimensional cross-linked network structure. [49][50][51][52][53][54][55] Generally, epoxy-curing agents can be divided into two major classes: apparent curing agents and latent initiators. Apparent curing agents are further divided into two types: addition polymerization curing agents (such as amines, acid anhydrides, and phenols) and catalytic curing agents (such as imidazoles, tertiary amine, and B 3 F complex).…”

Epoxy Adhesives with Reversible Hardeners: Controllable Thermal Debonding in Bulk and at Interfaces

“…[44][45][46][47][48][49][50][51][52] More specifically, polyamide hardeners for epoxy systems are a well-known functional type of amino polyamide curing agents and they are frequently used to add flexibility and toughness to traditional epoxy formulations without sacrificing thermal stability. [46,[53][54][55][56] Nonetheless, because of their inherent bond strength, amide bonds are generally thought to be irreversible due to their molecular design.…”