HIGH STRENGTH - HIGH MODULUS GLASS FIBERS

Glass fibers drawn from compositions located in the SiO2-Al2O3-ZnO system possess tensile strengths in excess of 800,000 psi. Glass fibers drawn from compositions in the SiO2-Al2-O3-MgO system have given similar results, particularly at fiber diameters in the 0.00015 to 0.00020 inch range. The modulus of elasticity of glass fibers obtained from compositions located in the SiO2-Al2O3-MgO system can be increased to 16.0 x 10 to the 6th power psi. This is accomplished by lowering the fiber diameter to the 0.00015 to 0.00020 in. range. In the SiO2Al2O3-Na2O system, the fiber forming temperature, the tensile strength and the modulus of elasticity change with composition in a manner which gives a break in the composition vs. property curves at the point where the Al to Na ratio is 1. This is related to the change in the coordination number of the aluminum at this ratio, proposed in the literature. The properties measured for glasses in the SiO2-TiO2-K2O system do not appear to lead to as clear a concept of glass structure. Properties vary gradually with composition, with no evidence of a sharp break at any point.