On the optical properties of glass particle-filled transparent polymers with similar refractive indices
Fillers can be used to improve and modify the properties of plastics and thus adapt them to their field of application. The potential that fillers offer by improving the properties cannot be exploited, or only to a limited extent, with transparent materials. Fillers reduce the transparency because of light scattering and absorption or inhibit it completely. One way to sustain transparency is to use transparent fillers, which have a similar refractive index to the transparent polymer matrix. Glass particles as fillers cause higher stiffness and lower thermal expansion due to their properties. Since plastics and glasses, however, have different thermo-optical coefficients and often a different refractive index, temperature or wavelength changes as well as several wavelengths in combination, cause light scattering.
In this work, the optical properties of transparent glass particle filled polymers with similar refractive indices are investigated with regard to the material properties and the geometrical arrangements. The angle-dependent light scattering of different particle sizes as well as the imaging quality of the composites are considered. Subsequently, the application potentials of these materials are derived. The composites exhibit a temperature- and wavelength-dependent transmission. Based on this property, the new field of application for fiber-optic temperature measurement is developed.