Determination of particle size distributions and the degree of dispersion in nanocomposites

Objective of this study was the investigation of measurement techniques to determine the quality of the dispersion process of nanoparticles in polymer composites. In order to prepare the matrix suspension, alumina nanoparticles were dispersed applying shear mixing techniques in a high performance laboratory kneader. The product quality in liquid state was determined by means of dynamic light scattering (DLS) and centrifugal sedimentation analysis (CSA). However, particle measurements in carrier fluids like epoxy resin are complex and challenging. Measuring values like particle size distribution and grade of homogeneousness are strongly influenced by the sample preparation and adjustments of the measuring device. Within this study the machine settings and the formulation was analysed systematically. Hereby an identification of the key parameters and an optimisation of the measuring process were possible. Additionally, the composite was cured and analysed by scanning electron microscopy (SEM). Finally all measuring techniques were evaluated and compared among each other. Thus, DLS is the fastest method to measure spherically particles in the liquid matrix, CSA allows a certain deviation from the spherical shape and SEM gives a qualitative impression of the final particle size in cured composite condition.