If fillers can be added to transparent materials without losing transparency, then advantages like enhanced mechanical and thermal properties can be integrated. The investigated specimens consist of glass particles and refractive index oil as a model for transparent matrices with a very similar refractive index. Their optical properties and resulting limitations are described. Potential uses are also demonstrated by application-oriented optical testing. Besides a standard spectrometer, additional spectrometer setups were used. These include a diffuse as well as a collimated illumination and different sample positioning. Furthermore, the scattered light intensity was measured at different angles. This analysis reveals that composites with smaller particles transmit more light directly. In contrast, standard spectrometers indicate an increasing direct transmittance of composites with larger particles. They collect significant amounts of scattered light and, therefore, are not suitable for transmission measurements of such composites. The different positioning shows that all specimens exhibit very little scattering when placed directly on a diffuse light source. With a greater distance between specimen and light source, the scattering increases strongly. To display the composites' optical appearance, the light-dark-contrast of the diffuse white light source photographed behind the composite was analyzed. Both long and short distances between composite and light source lead to a precise image of the light source. Nevertheless, the white light source appears in the color of the wavelength with matching refractive indices at long distances.
Protecting ultra- and hyperhydrophilic implant surfaces in dry state from loss of wettability
