Acid-base interfaces in fiber-reinforced polymer composites

Abstract

The role of Lewis acid-base interactions at the fiber-matrix interface in composites is studied with both glass and Teflon fibers. In the glass fiber case, surface chemistry is modified with amino-, methacryloxy-and glycidoxy-silane coupling agents (A-1100, A-174 and A-187, respectively). Silane adsorption mechanisms as well as the properties of filament-wound, unidirectional epoxy and polyester composites are explained by a combination of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and flow microcalorimetry. The heats of adsorption of pyridine and phenol prove that the coupling agents add acidic sites to the glass fiber surface as well as stronger basic sites. The subsequent adhesion of the matrix polymers and the short beam shear strengths of composites are explained on this basis. The Teflon fibers are first etched with sodium naphthalene solutions, and then sequentially hydroborated and acetylated, producing approximately monofunctional hydroxyl (acidic) and ester (basic) groups on the surfaces, as determined by XPS, FTIR, and electrophoretic mobility analyses. Composites prepared with the acetylated fibers and a chlorinated polyvinyl chloride (acidic) matrix are superior in tensile properties, and SEM fractography shows PTFE fibrillation, indicative of good fiber-matrix adhesion and stress transfer, in this case only.

Aqueous Amino Silane Modification of E-glass Surfaces

“…It has long been known that treating the surface of a silica filler (colloidal, particulate, or fibrous) with a coupling agent improves the physical and chemical properties of a polymer matrix filled with such materials (1)(2)(3)(4). The match between polymer matrix and silane organofunctional group type and length has a bearing on the mechanical properties of the product (5).…”

Treated Glass Fibers: Part I, Adsorption of an Isocyanurate Silane

“…1) from aqueous solution, displayed the typical smooth surface morphology (Fig. E-glass fibers (1 gm; Ahlstrom Glassfibre Ltd.; 11 mm thickness; BET surface area, 0.7 cm 3 /g; density, 2.50 g/cm 3 ; sized with pure water then 2a) seen previously (24)(25)(26). Identical treatment of the glass fibers with the isocyanurate silane, but from CCl 4 solution, resulted in unprecedented air dried and cut into 8 mm lengths) were magnetically stirred in a solution of the isocyanurate silane ( Fig.…”

“…2b), with the isocyanurate silane clustering or aggregating into hydrophobic domains. Such domain formation fibers were washed with CCl 4 (3 1 100 ml) and then oven dried at 120ЊC was once previously observed (24). The surprising SEM pictures revealed environments cannot remove all the surface water from glass.…”

Adsorption of an Isocyanurate Silane on E-Glass Fibers from Ethanol and Toluene

“…Previous SEM pictures of silane-coated glass fibers have revealed a smooth surface morphology (36,37). Treatment of glass fibers with isocyanurate silane from ethanol and toluene, respectively, revealed that the silane formed bridges between nearby fibers (Figs.…”