EFFECT OF SUBSTRATES ON THE STRUCTURE OF POLYMER INTERPHASES .1. OXIDATION OF AMINOSILANE PRIMERS

Infrared spectroscopy was used to determine the effect that metal substrates such as titanium, iron, 1100-series aluminum, 2024 aluminum, and copper have on the molecular structure and properties of gamma -aminopropyltriethoxysilane ( gamma -APS) primer films. When gamma -APS was adsorbed onto any of the substrates from aqueous solutions at pH 10. 4 for 1 min and then dried at room temperature for 30 min, the molecular structure of the primer films was similar and consisted of low-molecular-weight siloxane polymers containing a considerable amount of absorbed carbon dioxide in the form of amine bicarbonates. After the films were dried at elevated temperatures, the structures differed significantly. The reaction of primer films on iron and 2024 aluminum with epoxy resins at 75 degree C was slow because the temperature was too low for dissociation of the bicarbonates to occur. At 150 degree C, epoxies reacted readily with gamma -APS films on iron but not with those on 2024 aluminum. For primer films on 2024 aluminum, the preferred reaction at 150 degree C was oxidation of the amino groups.