Interfacial Mobility and Its Effect on Flexural Strength and Fracture Toughnessin Glass-Fiber Fabric Reinforced Epoxy Laminates

摘要

The differences in the behavior of composites with different adhesion promotershave been studied using NMR and mechanical property tests. The two coupling agents used were aminopropylsilane (APS, SiCH2CH2CH2NH2) and aminobutylsilane (ABS,-SiCH2CH2CH2CH2NH2). These exhibit similar chemistry, but differ in their dynamics at the interface. The use of the specifically deuterated coupling agents (DAPS and DABS) allowed them to be probed with solid-state deuterium NMR at the air and polymer interface (in a composite). A comparison of the dynamics of the two systems adsorbed on silica reveal multilayers form a graded interface with respect to molecular mobility. The layer directly in contact with the silica is the most rigid and the outermost layers are most mobile. In the outmost layers, DABS moves about 10 times faster than DAPS. To probe how differences in mobility of these interfacial layers affect the physical properties; composites of glass, coupling agent and epoxy resin were prepared. In terms of strength, modulus, and fracture toughness, it was found that either coupling agent gave improved properties. The properties of the APS system were also generally better than those in the ABS system. We postulate that these differences were due to the differences in mobility at the coupling agent/polymer interface.