(87a) NEXAFS Characterization of Thermoset/Substrate Adhesive Interfaces

Near edge X-ray absorption fine structure is an extremely sensitive surface science technique for examining carbon, nitrogen, oxygen, and fluorine edges. We utilize it mainly to examine the concentration of certain molecules which exhibit carbon-carbon g* transitions. Molecules like diglycidyl ether of bisphenol A (DGEBA) are often used in commercial epoxy formulations and fall into this category. Our experimental method involves first altering the surface chemistry of silicon wafers with various functionally reactive silane coupling agents. The silanes are then reacted with polyether amines intermediates followed by reaction with DGEBA. There are a number of different molecules we use for each of the first two steps which can; either passivate the surface or create reactive surfaces; create more or less dense local crosslink densities near the silicon surface. This leads to a highly tunable system for both adhesive bond strength and fracture strength at the interface. The screening process for the adhesive testing is enabled by the NEXAFS technique and our ability to decipher the total number of DGEBA molecules which adhere to any given surface treatment formulation.