Micro-macro characterisation of DGEBA-based epoxies as a preliminary to polymer interphase modelling

Possart, G., Presser, M., Passlack, S., Geiss, P.L., Kopnarski, M., Brodyanski, A. and Steinmann, P. (2009) Micro-macro characterisation of DGEBA-based epoxies as a preliminary to polymer interphase modelling. International Journal of Adhesion and Adhesives, 29(5), pp. 478-487. (doi: 10.1016/j.ijadhadh.2008.10.001)

Abstract

Reactive polymer adhesives in contact to substrates are known to form so-called interphases, a notion comprising the domain within which the polymer, compared to its bulk, exhibits structural inhomogeneities and gradients in material properties. Induced by the interface between substrate and polymer the formation of such interphases is usually ascribed to processes like segregation or phase separation of polymer components, selective adsorption, steric hindrance, orientation effects or curing shrinkage. Quantitative information on mechanical interphase properties is obtainable only by considerable efforts since interphases belong to the class of buried layers, i.e. they are located between bulk polymer and substrate, which impedes a majority of experimental techniques. Within this contribution, a two-component epoxy-based model polymer (DGEBA/DETA) is examined by methods on different scales and with respect to the effects that both the resin/hardener mixing ratio and the chemical structure of the hardener exert on the mechanical bulk properties. By means of these variations the above mentioned processes disturbing the polymer network formation in the vicinity of the substrate are emulated within the bulk. Macroscopic tension tests, nanoindentation and calorimetric methods (DSC) are applied to obtain relations between structural variations and material behaviour. Inversely identifying the governing parameters of suitable constitutive laws from experimental data will later conclude the first step towards a quantitative interphase model. It is demonstrated that modifications of the resin/hardener mixing ratio and the hardener formulation lead to variations in mechanical bulk properties which are quantitatively determinable by methods on different scales and do lie in ranges similar to those of property profiles that have been observed within interphases. In future work, the local mechanical behaviour of adhesive joints under load will then be investigated by a microscale videoextensometry. The resulting data will be compared to the structure-property relations from step one to conclude on the local polymer structure within the interphase.

• Item Type: Articles
• Additional Information: Financial support by the German Research Foundation within the collaborative Project PAK 108 is gratefully acknowledged.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Steinmann, Professor Paul
• Authors: Possart, G., Presser, M., Passlack, S., Geiss, P.L., Kopnarski, M., Brodyanski, A., and Steinmann, P.
• College/School: College of Science and Engineering > School of Engineering > Infrastructure and Environment
• Journal Name: International Journal of Adhesion and Adhesives
• Publisher: Elsevier
• ISSN: 0143-7496
• ISSN (Online): 1879-0127

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