Effect of molecular structure on mechanical properties of epoxy resins

Abstract

The effect of varying the molecular structure of epoxy resins on their mechanical properties when used as adhesives was studied. The work was directed toward preparation of bisphenols of the general formula HOϕCR(R′)ϕOH where R and R′ are either alkyl or alicylic substituents, in which case the benzhydryl carbon is incorporated in a cyclopentane or cyclohexane ring for use in the preparation of glycidyl polyethers having the formula: where B is the divalent hydrocarbon radical of the bisphenol and n is an integer of the series 0, 1, 2, 3… Preparation of 13 epoxy resins which are liquids at room temperature is described. The effect of varying the structure of the dihydric phenol in the epoxy resin on the strength of adhesive‐bonded joints was determined. The results indicate that relative bonding strengths of epoxy resins synthesized from various bisphenols can probably be attributed to the symmetry and chain length of the substituents attached to the carbon atom connecting the two aromatic nuclei. There is a high correlation between adhesive properties and steric influence of a substituted methyl group. Although the qualitative features of substitution on the central carbon atom are shown to be fairly well understood, there are a number of points that still require clarification. For instance, a more conclusive picture of the effect of branching is desirable. Also, there are uncertainties about the magnitude of the temperature effect and the influence of the substituent on the impact values.

Systematic coarse-graining of epoxy resins with machine learning-informed energy renormalization

“…Chemistry-specific molecular models are critically needed to bridge the gap in scales between molecular dynamics (MD) simulations and experiments, while predicting accurately the highly tunable macroscopic properties of epoxy resins and their composites 1-3 . This remains a challenging problem to tackle due to the chemical complexity [4][5][6] of epoxy resins, the high number of properties that must be targeted for realistic predictions, and their strong dependence on the degree of crosslinking (DC) [7][8][9][10][11][12] . This up-scaling problem requires multi-dimensional functional calibration, taking inputs from high-fidelity simulations such as all-atomistic simulations.…”

Adhesion Promoting Copolymer of Acetate-Protected Vinyl Catechol with Glycidyl Methacrylate: Unraveling Deprotection, Adsorption, and Adhesion Behaviors on Metal Substrates

“…14,15 The adhesion performance of epoxy adhesives can be improved by increasing the mechanical properties by changing the chemical structures of monomers or adding reinforcements. 16,17 Theoretically, the maximum adhesion strength of an adhesive-bonded lap joint could be approximately close to the shear strength of the adhesive itself. However, the measured lap shear strengths are typically much lower than the maximum value because of the relatively weaker interfacial interactions between adhesives and adherends.…”

“…Adhesion, a process to firmly stick similar or dissimilar substances (interfaces) with adhesives, is an ancient and extremely important technique that marks the evolution of humans in terms of tool development. − Adhesion techniques have been widely utilized in our daily lives and are implemented in numerous industrial applications such as in aerospace, footwear, automotive, biomedical, and electronic industries. − With respect to the development of synthetic adhesive materials, several categories of adhesives such as solvent-based and curable adhesives have been fabricated with a wide variety of polymer materials. ,− Among various adhesives, epoxy resins are one of the important and widely used thermosetting adhesives in the industry and are used as sealants, coatings, and structural adhesives because of their excellent mechanical properties, high thermal and chemical stabilities, and relatively low gas and water vapor permeabilities. , The adhesion performance of epoxy adhesives can be improved by increasing the mechanical properties by changing the chemical structures of monomers or adding reinforcements. , Theoretically, the maximum adhesion strength of an adhesive-bonded lap joint could be approximately close to the shear strength of the adhesive itself. However, the measured lap shear strengths are typically much lower than the maximum value because of the relatively weaker interfacial interactions between adhesives and adherends.…”