Peroxide Crosslinkable Cable Compounding
Polyethylenes (PE) have outstandingly good insulation properties. A temporary temperature rise, e.g. due to peak loading, can however cause a complete breakdown of PE cable insulation. The relatively low softening or melting point leads to thermo-mechanical failure or even dripping of the Insulation. Cross-linked polyethylene (PEX) is more thermosetting than thermoplastic. It can therefore be used at significantly higher operating temperatures, is mechanically stronger, more resistant to organic liquids, and often enables thinner wall thicknesses. Various cross-linking methods are used.
Compounding requirements for peroxide crosslinkable cable compounding
The formulation components for these applications have to be intensively mixed at strictly controlled temperatures, with high plant and product purity. For MV applications the liquid peroxide is directly injected into the melt pool and intensively mixed at low temperatures. The compound is then melt filtered and pelletized. For HV applications, the compounding line is designed and operated to ensure the highest purity. The base polymers are prefiltered and contamination sources are eliminated both internally and externally, so that production takes place under cleanroom conditions.
The success factors of the BUSS Co-Kneader within the whole compounding system in this connection are as follows. Peroxide is directly injected into the process zone and optimally distributed by intensive mixing immediately afterwards. Uniformly moderate shear rates make sure that this occurs at low process temperatures with the least possible polymer breakdown. The cascaded line arrangement of the BUSS Kneader and discharge extruder, furthermore enables product-considerate melt filtering and pelletizing as well as optimal and efficient equipment start-up and operation.
As a reference for this industry, all the compounding lines successfully realized so far exemplify the perfect fusion of BUSS expertise in process technology, plant engineering and design.