Polycondensation polymer-based composites of treated fibers

Mechanical properties of composites depend not only on properties of their constituents (fiber, matrix), but also of the interface fiber-matrix.; In this work, to improve fiber-matrix interfacial adhesion, we have realized modifications of fiber surface of Kevlar and glass. These processings and their influence on mechanical properties of fibers and composites have been studied by different methods of analysis. The chemical modification of the surface of Kevlar fibers processed to the plasma (so as to introduce active groups as OH or NH{dollar}sb2{dollar}) at the fiber surface, has been realized in order to improve the interfacial adhesion. The surface of fibers has been used as support for the interfacial polymerization. Nylon-6,6 has been synthesized successfully in this manner. The grafted nylon has been characterized by X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry and by an extraction procedure.; The interfacial polycondensation used in the first work has been studied in detail to follow the reaction. Two types of treatments have been realized on the surface of Kevlar as well as of glass fibers. These are abbreviated SSP (single pass procedure) and MPP (multiple pass procedure). Measures obtained by nuclear magnetic resonance on SSP samples, indicate that there is not bridging reaction. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) have been used to characterize products of MPP. It has been shown that the quantity and that the molecular mass of the nylon grafted to the surface increases with the number of passages.; Following this work, the surface of glass fiber was used as solid support by the interfacial polycondensation of nylon-6,6 and composite of nylon-6,6/grafted glass fiber have been manufactured. Chains of nylon have been grafted on free hydroxyl OH groups situated at the fiber surface. The grafted nylon has been observed by scanning electron microscopy. The effect of the processing on the fiber-matrix adhesion has been explored by measuring the interfacial shear strength by means of the fragmentation test. The two parameter Weibull function has been used to allow analysis of these experimental results.; To modify short fibers, nevertheless, a new strategy has been proposed. Covalent bonds whose presence is responsible for a good interfacial adhesion, makes difficult the composite processing by increasing the viscosity of the system. Ionic bonds have been established to the fiber-matrix interface. The interfacial polymerization of nylon followed by the ionic groups introduction of type quaternary amine has been realized on the surface of glass fibers. The average fiber length after processing increased, which was attributed to a decrease in fiber friction during the mixing process. Mechanical properties in tensile and in flexion have been increased. (Abstract shortened by UMI.)...