Nanocomposites are commonly manufactured on a compounder, an extruder equipped with multiple screws. This manufacturing technic allows the large scale production of well dispersed mixtures of solid particles in polymer melt. Progress in the development of new functional fabrics is limited by the sophisticated de-agglomeration characterisics of some filler types. Dispersions made by conventional systems still contain large agglomerates that are hindering further processing at a good quality in terms of tensile strength and breaking resistance. Therefore, in this study ultrasonication is applied to achieve the de-agglomeration of such agglomerates that could not be dispersed in the previous compounding step. The construction and implementation of a novel ultrasonication device in an extruder is aggravated by the heavy operation conditions of the system. High temperatures above 250 °C have to be kept away from the piezoceramic transducers. Pressures exceeding a level of 50 bars result to a damping of the sonotrode momentum and cavitation intensity. Two different applications facing the technical challenges of this ultrasound application are presented. A summary of the experimental results for improving the dispersion of agglomerates is given as well.