Nanoparticles in Organic Solvents with Polymers – Stability and Consequences upon Material Synthesis through Spray Drying and Melt Moulding

Abstract

It is a well accepted fact that nanoparticles and their industrial and commercial use have the potential to improve properties of modern materials substantially. Especially polymeric materials are attractive for incorporating nanoparticles with special properties only apparent in the nanoscale. One main consideration in processing such composite materials is to prevent the nanoparticles from agglomerating or even worse aggregating. In this paper a modular process method is presented based on a mixture of sterically stabilized nanoparticles in an organic solvent with soluble polymers and subsequent spray drying to quickly yet thermally carefully remove the solvent. The method has the potential for large scale production of highly filled nanoparticle-polymer-composites. However the bottleneck of this method is the unknown interaction of polymers and stabilized nanoparticles. We present the impact of depletion flocculation and subsequent phase separation or stabilization by adsorbing polymers on the dispersion of the nanoparticles. It is shown that the processing method is more adequate when compared to traditional melt moulding. The best magnetite nanoparticle stability in dichloromethane is achieved using ricinoleic acid. Besides flocculates we can identify separate primary particles in the composite. The size of the floccules is in the lower micrometer range for nanoparticles 15 nm in size.