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Recent Progress in the Studies of Molecular and Microstructure of Interfaces in Composites, Coatings and Adhesive Joints.
CASE WESTERN RESERVE UNIV CLEVELAND OH DEPT OF MACROMOLECULAR SCIENCE
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Recent progress in the studies of molecular and microstructure of interfaces and interphases in composites, coatings and adhesives joints is reviewed. Remarkable progress has been made in elucidating the structure of silane coupling agents and their function with respect to dry and wet strengths of multiphase systems. Aminosilanes attracted major effort in the past. It is now understood that the structure of partially cured hydrolyzate is complicated. When adsorbed from a natural pH solution and dried in air at room temperature, approximately half of the amine group for amine bicarbonate salt with the C02 in air. The rest of the amine groups are either intra-or intermolecularly hydrogen bonded to neighboring silanol groups or free from hydrogen bonding. There exists chemical bonding at the glasssilane or metalsilane interfaces. The surface characteristics, including acidity, topology and homogeneity, influence the structure of the coupling agent. The coupling agent interphase shows a gradient in various properties. Silanes tend to be ordered in the interphase and the degree of organization depends largely on the organofunctionality. The orientation and organization of the silane affect the reinforcement mechanism. There are chemisorbed and physisorbed silanes in the interphase.
APPROVED FOR PUBLIC RELEASE