Advanced Concepts in Nanotexturing of Solid Surfaces for Composite Applications; Conference paper

摘要

The overall goal of this paper was to determine which factors of silane/silica chemistry most influenced surface coverage and surface roughness of glass surfaces. Nanotexturing of glass fibers has shown the potential to improve impact properties of glass reinforced composites. Previous work by Army researches determined that modifying fiber surfaces using a mixture of silane coupling agents that were both reactive and non-reactive towards the matrix phase, in conjunction with nanoscale colloidal silica, yielded a simultaneously high strength and tough composite. The focus of this work was to ascertain which factors of the silane and silica treatments were most influential in controlling the silica deposition on solid surfaces. The basis of the silane chemistry involves controlling the number of amine-functional groups on the fiber surface. Propyltrimethoxylsilane (PTMO) and aminopropyltrimethoxysilane (APS) are silanes that contain a propyl group and a primary amine, respectively. By varying the ratio of these silanes in solution, the concentration of amine groups on the fiber surface can be controlled. The amine groups on the fiber surface act as potential sites for epoxy-amine reactions. Two routes were chosen for affixing silica to the surface using the amine groups. In the first route, a reverse silane reaction is carried out; where the epoxy groups of a non-hydrolyzed glycidylpropyltrimethoxysilane (GPS) react with surface amine groups. Upon hydrolysis, the methoxy groups of the silane are converted to hydroxyl groups that undergo a condensation reaction with the silica. The second route for silica deposition involves the functionalization of the silica. In a separate step, hydrolyzed GPS is reacted with the silica to yield epoxy-functional silica. The epoxy groups on the silica can react with the amine groups on the glass surface.