TECHNIQUES AND OPTIONS FOR IMPROVED TWIN-SCREW COMPOUNDING OF REINFORCED POLYOLEFINS

摘要

Application requirements for polyolefin compounds continue to push the performance envelope with respect to, for example, improved mechanical properties such as flex modulus, tensile strength, and heat distortion temperature; aesthetic properties such as surface quality; processing characteristics such as viscosity; and as always, cost. In order to attain required properties such as those listed above, compound formulations can be very complex, but invariably will require fiber and/or mineral filler reinforcement. For reinforcement to be effective, fibers and minerals each have specific compounding requirements. Fibers, whether roving or chopped, need to be unbundled as well as maintain a critical length during the compounding process. Minerals, depending on their structure, need to be distributed and/or dispersed and distributed. The co-rotating twin-screw compounder has long been the equipment of choice for such compounding functions. However, compounders still face processing challenges such as, how to incorporate a high loading of low bulk density mineral filler and maintain an economically viable production rate, how to maximize fiber length in high viscosity high mineral filled formulations, how to eliminate (or at least minimize) the possibility of contaminants, such as black specks, in the finished product, and how to enhance productivity. This paper will review many of the basic requirements for compounding reinforced polyolefins as well highlight recent innovations in Co-rotating Twin-screw technology that have enhanced product quality and productivity for these materials.