Structure and properties of organosilane primers for adhesive bonding

• Published in: Applications of surface science Vol. 7; no. 1; pp. 19 - 31
• Main Authors: Boerio, F.J., Williams, J.W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1981
• ISSN: 0378-5963
• DOI: 10.1016/0378-5963(81)90057-X

Reflection—absorption infrared spectroscopy was used to determine the structure of films formed by the adsorption of γ-aminopropyltriethoxysilane (γ-APS) onto iron mirrors from aqueous solutions. Films formed at the natural pH of 1% aqueous solutions were composed of oligomers characterized by infrared bands near 1550, 1470 and 1130 cm -1 while films formed at pH values less than about 9.0 were composed of polysiloxanes characterized by bands near 1600, 1500 and 1135 cm -1. The polysiloxanes formed at low pH values were much more effective as primers for improving the hydrothermal stability of iron/epoxy lap joints than the oligomers obtained at high pH values. Joints prepared from substrates primed with γ-APS at pH = 8.0 retained about 70% of their strength after immersion for 60 days in water at 60°C while those prepared from substrates primed at pH = 10.4 retained only about 50% of their strength. By comparison, joints prepared from unprimed substrates retained only about 25% of their strength after such exposure.