Epoxy/Poly(ethylene‐co‐methacrylic acid) Blends as Thermally Activated Healing Agents in an Epoxy/Amine Network

Abstract

Thermally activated healing of a cured epoxy/amine network using di-glycidyl ether of bisphenol A (DGEBA) and triethylene-tetramine (TETA) was explored using a modified thermoplastic poly(ethylene-co-methacrylic acid) (EMAA) healing agent. Epoxy resins of differing molecular weight were blended and pre-reacted with EMAA to heal via covalent and non-covalent bonding. Healing depended strongly on compatibility and reactivity between the epoxy additive and EMAA. Reduced compatibility and preferential miscibility produced the greatest healing, while increased compatibility and epoxide chemical reaction reduced healing. More healing was achieved when the availability of reactive epoxide groups from the healing agent and amino groups from the amine rich DGEBA/TETA polymer networks both increased.

Analyzing the network formation and curing kinetics of epoxy resins by in situ near-infrared measurements with variable heating rates

“…The epoxy conversion can also be measured directly by structural changes using spectroscopic methods like near-infrared (NIR) [4,[22][23][24][25], mid-infrared (MIR) [26][27][28][29] or Raman [30][31][32] spectroscopy. In the NIR region bands are often difficult to evaluate due to mode coupling and overtones, hence MIR spectroscopy is often preferred to analyse chemical composition.…”

Thermal mending in novel epoxy/cyclic olefin copolymer blends

“…In order to effectively heal the cracks, a thermoplastic healing agent should possess three key features: (i) low melting/softening point and viscosity to achieve flowability of the healing agent in the cracks, (ii) functional groups being reactive to the hosting matrix, and (iii) good adhesive properties to obtain a strong hydrogen bonding with the matrix during crack mending [23]. Up to now, various thermoplastic matrix have been investigated as possible healing agents for thermosettings, such as (poly(bisphenol-A-co-epichlorohydrin) [24][25][26], poly (ε-caprolactone) (PCL) [27][28][29], poly(vinylacetate) (PVAc) [30], poly(ethylene-co-methyl acrylate) (EMA) [31] and poly(ethylene-co-methacrylic acid) (EMAA) [32,33]. For instance, Hayes et al [24,25] considered a linear copolymer (polybisphenol-A-coepichlorohydrin) thermoplastic healing matrix in an epoxy resin, reporting an healing efficiency under impact conditions of 65% with an healing agent concentration of 7.5 wt%.…”

Solid-state healing of resins and composites

“…These features were all clearly observed on the fracture surfaces of the respective thermoplastic additives as shown in Figure 3.39b-d, which compared EVA and PEGMA with EMAA. More recently, EMAA was modified with different epoxy resins to explore better and more durable healing by incorporating more covalent bonding into the healing mechanism [51]. To do this, DGEBAs of varying molecular weights and reactivities were blended with EMAA, cryogenically ground into particles of varying sizes, and cured with an epoxy/amine resin.…”