As a general rule, your nanoparticle dispersion in the extruded product will only be as good as it was before extrusion and the extrusion process is not likely to significantly break up aggregates or otherwise improve dispersion. In other words, you should work on obtaining good dispersion in your dispersant/particle feed before compounding with the polymer. You will likely find more sources in the CNT/TiO2/clay literature for this type of compounding, but the principle should be similar for metal nanoparticles.

The entire Chapter 5 titled Preparation of filled polymer systems pages 175-242 in the book Aroon V. Shenoy, Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Netherlands (1999) is dedicated to the mixing/blending/compounding of fillers into polymer melts. The sections include Goodness of mixing, Mixing mechanisms, Compounding techniques, Compounding/mixing variables. In section 5.4, there is a detailed discussion on the compounding /mixing variables that affect the quality of the mix. Some variables are more sensitive to changes than others. It is important to study and identify these variables and understand their sensitivity so that the compounding /mixing can be carried out under optimum conditions. Variables affecting compounding operations could be machine variables (mixer type, rotor geometry) or operating variables (mixing time, rotor speed, ram pressure, chamber loading, mixing temperature, order of ingredient addition). You will have to study and understand the effect of each of these variables for your specific metal nanoparticle filler – ABS polymer matrix combination to find the optimum conditions to achieve the proper level of dispersion and distribution of filler into the polymer. You will get the necessary hints on how to go about this by reading Chapter 5 of the book.

In the Table 1.12 of the book Aroon V. Shenoy, Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Netherlands (1999), there are many suggested surface modifiers that would work for the ABS matrix – A-174, A-187, CM8550, CG6720, MEMO, GLYMO, Z-6030, Z-6040. These are silanes, and their full forms are given in Table 1.8. Which one would be most effective for the metal nanoparticles that you are using can only be worked out by some mixing experiments, which are discussed in the book.

Further, in case you need to understand the important factors in preventing flow defects and controlling the quality of the material that is produced during extrusion process, then you may get some idea about it by reading the Section 8.4 of Chapter 8 on Extrusion in the following book: A. V. Shenoy and D. R. Saini, Thermoplastic Melt Rheology and Processing, Marcel Dekker Inc., New York (1996). Twin-screw extrusion may be better than single-screw extrusion for achieving better dispersion and break-up of agglomerates. Running the same material twice through single-screw extrusion may not provide additional benefits like what twin-screw extrusion would provide in a single run.