Determine surface and interface chemistries using XPS surface analysis:
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Surface analysis of adherend or substrate material as prepared for bonding
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Surface analysis of both sides of peeled or failed interfaces to find locus of failure, identify chemistry, and identify any contaminants
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Correlate surface chemistry of samples tested to failure with measured strength
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Aging of bondline, test to failure, determine effects of aging on chemistry
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Determine differences of bondline adhesive chemistry from the bulk adhesive chemistry, since distinct interfacial adhesive interphase layers are common
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Identify interfacial contaminants due to hydrolysis, silicones or siloxanes, plasticizers, surfactants, hand lotions, cutting oils, hard water deposits, solder fluxes, and photoresists
Prepare very clean adherend surfaces for reference to mechanically tested bond strengths of manufactured or prototype bonded materials.
Microscopy - SEM and Optical - Failure Analysis:
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Locates failure plane
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Indicates type of failure
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Reveals gas bubbling effects due to contaminants or improper 2-part adhesive mixtures
Thermal Analysis:
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TMA to determine differences of thermal expansion of adherends and adhesive
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TMA to indicate whether thermoplastics have too much crystallinity, which may produce a large thermal expansion spike at the crystalline melting temperature
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TMA and DSC to determine maximum temperatures appropriate for curing adhesive bondlines or to prevent phase changes and degradation processes in use
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DSC to determine good adhesive curing conditions or problems due to improper mixtures of 2-part adhesives
Electrochemistry - Electrochemical Impedance Spectroscopy (EIS):
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Measures water and ionic concentration buildup in organic coatings and adhesives
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Measures effect of adhesive or coating pores, holidays, and fisheyes upon water reaching interface to cause hydrolysis attack of bondline
FTIR Spectroscopy Analysis:
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Identify differences at bondline relative to in the bulk of the adhesive
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Contrast chemistry of 1 μm depth to that of the 8 nm measured by XPS
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Identify plastic, rubber, resin, and laminate materials being bonded
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Identify the adhesive and/or the primer to which adhesive is applied, as it often is in aerospace adhesives bonds to aluminum surfaces
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