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Interphase characterization via the stiffness contrast of a scanning force microscope in displacement modulation mode
Author(s) -
Munz M.,
Sturm H.,
Schulz E.
Publication year - 2000
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/1096-9918(200008)30:1<410::aid-sia846>3.0.co;2-g
Subject(s) - diglycidyl ether , materials science , stiffness , composite material , epoxy , interphase , cantilever , bisphenol a , biology , genetics
The physical properties as well as the thickness of the interphase between polymer and reinforcing phase are generally expected to show a strong influence on the macroscopic mechanical properties of composite materials. In this study the scanning force microscope (SFM) has been applied for detecting stiffness gradients near the interface between copper and epoxide. In displacement modulation mode the load exerted by the tip is modulated sinusoidally by vibrating the normal position of the cantilever or the sample. The corresponding amplitude of dynamic cantilever bending is related to local surface stiffness. Thus, using the SFM, the local mechanical properties of the surface under investigation can be probed. When scanning the tip across the reinforcement/polymer interface, the polymeric interphasial zone can be identified with the observed stiffness gradient. For a commercial epoxide based on diglycidyl ether of bisphenol A (DGEBA) cured with an amine‐containing hardener, a stiffness gradient was detected that could be fitted by a Gaussian profile typical for diffusional processes. The width of the stiffness gradient was ∼280 nm. The observation is discussed in terms of interface‐induced segregation processes between resin and hardener, as well as heat conduction mechanisms that can occur during the exothermic curing reaction. Both mechanisms are diffusional in nature and, via the local network structure, are expected to show some influence on the local stiffness of the cured epoxy. Copyright © 2000 John Wiley & Sons, Ltd.