The compounding system is critically important for all Polycarbonate (PC) based materials. PC ingredients, mostly in powder or chip form, are compounded together with additive components into pellets such as for transparent moulding compounds in the compounding system. In many cases reinforcement agents, flame retardants, dyes or the aforementioned blend partners are also added. Compounding these materials is therefore very demanding and requires customized solutions such as some of the following. Polymer components must be melted as gently as possible, flame retardants have to be perfectly distributed, and reinforcement fibers must be added and processed in such a way as to optimize mechanical properties.
All these requirements are well mastered by sophisticated compounding process technology accordingly. The BUSS Kneader can make much better use of its strengths here than other compounding systems. Thanks to extremely uniform and moderate shear rates, yellowing is minimized because no hotspots occur. This is critically important for transparent formulations. Moreover the BUSS Kneader’s characteristically perfect handling of wide viscosity ranges enables very wide and dependable operating windows. PC blends, reinforced, flame retardant or high-viscosity formulations and other combinations can usually be compounded without any change in screw geometry.
The BUSS Kneader’s two-stage system clearly separates the compounding and pressure build-up stages so that each stage can be independently optimized. Pressure build-up for pelletizing PC compounds is usually by gear pump.