Structural effect of phenalkamines on adhesive viscoelastic and thermal properties of epoxy networks

Abstract

Phenalkamine, the Mannich reaction products from cardanol, formaldehyde, and polyamines were prepared using ethylene diamine, diethylene triamine and triethlene tetraamine. These products were characterized by high-pressure liquid chromatography (HPLC), infrared spectroscopy, and nuclear magnetic resonance spectroscopy (1H NMR). Clearly resolved peaks due to presence of triene, diene, monoene, and saturated side chain containing species of cardanol were observed in HPLC. The presence of characteristic methylene linkages of Mannich bases at d 3.5-4.0 ppm was observed by 1H NMR. These curing agents were reacted with diglycidyl ether of bisphenol-A at room temperature and the curing times were optimized. The cured resins showed good adhesion with different metal surfaces particularly higher values were observed with copper due to its high surface energy. The viscoelastic properties of the cured samples were determined by dynamic mechanical thermal analysis. The storage modulus (E 0 ) was found to be in the order of 10 9 Pa and tan d values are around 908C. A reduction in storage modulus (E 0 ) and an increase in tan d values on postcuring were observed. Thermogravimetry analysis showed two-stage degradation above 2508C for the cured samples.

Engineering superior toughness in commercially viable block copolymer modified epoxy resin

“…Amine‐based curing agents, such as aliphatic and aromatic amines, and polyamides, have been well studied as model systems for block copolymer modified epoxy materials . Unlike these relatively simple compounds, C541 is a phenalkamine endowed with multiple desirable properties, including the ability to achieve high crosslink density, being active at low temperature, and having good chemical and water resistance . However, the amphiphilic molecular structure of C541 (i.e., a nonpolar hydrocarbon tail and a polar phenol and ethylenediamine head group) leads to complex curing kinetics and complicated thermodynamic interactions when mixed with epoxy monomers and the PEO‐PBO toughening agent.…”

“…8 Unlike these relatively simple compounds, C541 is a phenalkamine endowed with multiple desirable properties, including the ability to achieve high crosslink density, being active at low temperature, and having good chemical and water resistance. 61,62 However, the amphiphilic molecular structure of C541 (i.e., a nonpolar hydrocarbon tail and a polar phenol and ethylenediamine head group) leads to complex curing kinetics and complicated thermody-namic interactions when mixed with epoxy monomers and the PEO-PBO toughening agent. The curing accelerator DMP-30 (Ted Pella) is mainly composed of tris-(dimethylaminomethyl) phenol, which promotes epoxy to epoxy or hydroxyl to epoxy reactions and does not serve as a direct crosslinking agent.…”

New aromatic amine based on cardanol giving new biobased epoxy networks with cardanol

“…In previous works, cardanol was studied as it brings partial rigidity and good mechanical and thermal properties due to its aromatic ring. The Mannich reaction of cardanol with formaldehyde and some amine such as diethylene triamine [14][15][16] leads to partially biobased phenalkamine [17], Figure 2. The high hydrophobicity of these commercial phenalkamines provided by the long linear side chain also brings many benefits to coating formulations compared with other hardeners.…”

Influence of epoxidized linseed oil and sisal fibers on structure–property relationship of epoxy biocomposite

“…Thus, bio‐based curing agents are necessary for developing sustainable bio‐based epoxy networks from renewable resources that overcomes brittleness and provides flexibility. Cardanol‐based phenalkamines (PKAs) are commercially used as bio‐renewable crosslinkers for epoxy with advantage of low temperature curing applications even under wet or humid conditions . Additionally, PKA provides excellent stiffness‐toughness balance along with chemical resistance, hydrophobicity, flexibility and long pot life .…”