Polymer Interphases in Adhesively Bonded Joints – Origin, Properties and Methods for Characterization

Abstract:

Chemically curing adhesives are formulations requiring reactions to convert from liquid to solid. Once cured, these adhesives carry the potential to create strong load bearing joints, resisting even severe detrimental service conditions. In adhesively bonded joints with chemically curing adhesives the term "interphase" relates to the adhesive volume adjacent to the surface of the adherent (interface), which generally will exhibit properties different from those of the adhesive bulk polymer. The properties of these interphases play an important role concerning the performance and durability of structural adhesive joints. Therefore localized strain analysis in the cross-section of shear-loaded adhesive joints was performed by combining a high-precision mechanical testing device with digital microscopy and by developing a method for preparing, marking, and digitally tracking the local deformations in micro shear specimen. Non-uniform shear profiles developing in the cross-section of the adhesive joints after exceeding the yield point serve as a sensitive indication for mechanical surface-affected interphase properties and it could be observed, that deranged crosslinking promotes strain softening of the polymer in the interphase. Infrared analysis of the cross-sectional interphase region in adhesively bonded joints was performed with a Bruker Tensor II Fourier Transform Infrared (FTIR) spectrometer equipped with a Hyperion 3000 microscope with a 20x ATR germanium crystal objective and a MCT-Focal-Plane-Array-Detector (FPA), allowing to conduct high resolution chemical imaging and localized chemical analysis.

• Periodical: Materials Science Forum (Volume 941)
• Pages: 2249-2254
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.941.2249
• Online since: December 2018
• Authors: Paul Ludwig Geiss*, Melanie Schumann
• Keywords: Adhesive, Interphase, IR Microscopy, Micro Extensometry, Stress-Strain Analysis

References

[1] Possart, W., Krueger, J.K., Wehlack, C., Mueller, U., Petersen, C., Bactavatchalou, R. and Meiser, A., C. R. Chim. 9, 60-79 (2006).

[2] Knollman, G.C., Int. J Adhes. Adhes. 5, 137-141 (1985).

[3] Chung, J., Munz, M. and Sturm, H., Surf. Interface Anal. 39, 624-633 (2007).

[4] Safavi-Ardebili, V., Sinclair, A.N. and Spelt, J.K., J. Adhesion 62, 93-111 (1997).

[5] Parlevliet, P.P., Bersee, H.E.N. and Beukers, A., Compos. Part A – Appl. Sci and Manuf. 38, 651-665 (2007).

[6] P. L. Geiss and M. Schumann, J. Adhes. 88, 941-955 (2012).

[7] Smith, R.E., F.N. Larsen, and C.L. Long, Epoxy resin cure. II. FTIR analysis. J Appl Polym Sci, 29, 3713-3726 (1984).

DOI: 10.1002/app.1984.070291207

[8] Cañavate, J., et al., Polymer-Plastics Technology and Engineering, 39, 937-943 (2000).