Nanofiller materials for transparent polymer composites: Influences on the properties and on the transparency—A review

Filler materials are widely used in combination with polymer materials. Conventional filler particles generally cause light scattering and absorption because of their optical characteristic or refractive index difference. With nanoparticles (NPs) as a filler material, it is theoretically possible to manufacture transparent compounds due to their small particle dimensions reducing the interaction with light. Nevertheless, the particles tend to build agglomerates and aggregates which reduce the composite’s transparency considerably. This review gives an overview of the effect different particle materials have on the properties of transparent polymer composites with consideration of the composite’s transparency. There are very few reports on highly transparent and thick (>1 mm) polymer nanocomposites with such an amount of particles that affect other properties of the polymer significantly. In the majority of cases, NPs lead to a significant lower transparency. This indicates that the homogeneous dispersion of the particles is still a major difficulty in producing transparent nanocomposites with enhanced properties.