Controlling the nanostructure of epoxy resins: Reaction selectivity and stoichiometry

Abstract

The internal topology of epoxy resins is, for the first time, shown not to be the determining factor for small molecule transport. Whilst epoxy resins comprise the matrix component of many high performance composites, coatings and adhesives, the nanostructure and transport properties of these materials are not well understood. Here, peakforce AFM imaging, in-situ FTIR cure analysis and nanochemical AFM-IR imaging are used to establish the effects of reaction selectivity and stoichiometry on the nanostructure of epoxy-phenolic resins based on bisphenol-A and diglycidyl ether of bisphenol-A. In the presence of excess epoxy, resins transition from exhibiting homogeneous internal nanostructures to the familiar nodular morphology characteristic of epoxies. This occurs as a result of lower reaction selectivity in the presence of increasing catalyst concentrations.Surprisingly however, chemically similar stoichiometric resins with a heterogeneous nanostructure display improved resistance to corrosion breakdown (ion transport) and lower water uptake than the homogeneous resins.

Acid‐ and base‐catalyzedepoxy‐phenolthermosets from catechol, resorcinol and hydroquinone: Astructure–propertystudy

“…While most of the early studies on the reaction between DGEBA and bisphenol A (BPA) have focused on understanding the kinetics of linear chain formation and branching in the presence of a basic catalyst, 15–17 more recent studies have focused on the properties of the final thermosets. Morsch et al performed nano‐chemical imaging and nano‐thermal analysis on the networks formed by DGEBA, THPE and BPA and correlated the cross‐linking density to the water uptake and heterogeneities in the network structure 18–20 . Heise et al found that a range of cross‐linking densities and glass transition ( T g ) temperatures can be achieved by varying the BPA concentration 21 .…”

“…Morsch et al performed nano-chemical imaging and nano-thermal analysis on the networks formed by DGEBA, THPE and BPA and correlated the cross-linking density to the water uptake and heterogeneities in the network structure. [18][19][20] Heise et al found that a range of cross-linking densities and glass transition (T g ) temperatures can be achieved by varying the BPA concentration. 21 The T g values of base (imidazole) catalyzed DGEBA-BPA thermosets ranged from 60-80 C when the BPA concentration was varied from 50-25 mol%.…”

Correlated Materials Characterization via Multimodal Chemical and Functional Imaging

“…Quantitative analysis of nanodomains in polymer-based materials that relates chemical composition and localized thermal properties can be carried out using this approach. 45,48 AFM-IR has been used to confirm the uniformity of the polymerization reaction of PEDOT 49 and P3HT. 50 CNT-reinforced thermoset composites have been investigated revealing the distribution of chemical interfaces.…”

The synergistic effect of irregular alumina and round plates boron nitride binary‐particle system on the thermal conductivity of epoxy composites

“…Especially, with the development of miniaturization and high power of electronic devices and motors, efficient heat management is becoming a critical issue. [4][5][6][7] Generally, there are two methods to increase the thermal conductivity of epoxy resin: chemical 8,9 and physical [10][11][12][13][14][15][16] ways. The chemical method is designed for the epoxy resin molecular structure, and the improvement of its thermal conductivity is limited and high cost.…”