A novel technique for the study of coupling agent phenomena

A modification of the Internal Reflection Spectroscopy (IRS) technique for infrared (IR) spectroscopy is described, where the surface of the IRS element is modified by a thin (100 to 1000 å) layer of metal oxides, silanes or Kevlar so as to model the surface of reinforcements in composite materials. The modified IRS element is then brought into contact with the matrix material and chemical changes in the first 2000 to 3000 å of matrix examined by IR spectroscopy. Examples of the technique include a study of the effect of various surfaces on the crosslinking of an anhydride‐cured epoxy resin. The kinetics of the crosslinking process and the final ester crosslink concentration are shown to be significantly affected by, for example, a silica or Kevlar surface. The advantages and limitations of this modified IRS technique are discussed relative to other surface characterization techniques.