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Mechanically Induced reactions during Ultra-High Shear Polymer Processing

Exploitable results

The original purpose of this Basic Research project was to gain a deep understanding of the phenomena that occur when different polymers with or without fillers are submitted simultaneously to ultra high shear rates. The underlying reason for this fundamental research investigation was the existence of an ultra high shear process developed by Newplast which claims to produce polymer materials that exhibit good mechanical and other properties despite being produced from flakes or pellets of mixed polymer waste without the addition of chemical compatibilisers. A consortium consisting of Newplast (France) SA - a subsidiary of Newplast Holdings NV of Holland owners of the above mentioned ultra high shear process, three universities (Université catholique de Louvain, Belgium; Université des Sciences et Technologies de Lille, France; Universidade de Aveiro, Portugal), a research centre (CRIF, Belgium) and a roofing manufacturer (Derbit Spa, Italy) was established to investigate the fundamental science of this process. Additional aims were to extend the process to systems including fillers, model the process to improve its predictability, evaluate materials from the process for use in roofing materials and investigate the feasibility of scaling up and converting the process from a batch to a continuous one. Unfortunately, right at the start of the contract, Newplast went into liquidation denying the consortium access to the key equipment, materials and know-how on which the project had been based and thus all the tasks related to the Newplast process had to be abandoned. With the agreement of the European Commission, the project was repositioned to investigate whether any evidence of mechanical compatibilisation could be found in standard industry processing equipment. Draiswerke of Germany, manufacturers of the Gelimat mixer since about 40 years and also of the KEX Extruder, and Shell Research Belgium, with specific modelling and polymer expertise, joined the project. The project timetable was extended from 24 to 33 months. Using pre-existing industry equipment (mixers and extruders) and a wide variety of dual polymers systems, the research showed clearly that relatively high shear processes produce mechanical breaking of the polymer chains but no evidence was found for mechanical compatabilisation/grafting between different polymers. The equipment available to the consortium had shear rates of the order of 200 - 2000 sec-1 still substantially below the values likely in the Newplast process. Whilst this work shows that mechanical compatibilisation of polymers does not occur to any detectable extent in standard industry equipment, one cannot say whether or not this might occur in the Newplast process as this could not be investigated. Despite the major setbacks to the project posed by the demise of Newplast some other valuable results were obtained. These included: - Data on the successful replacement of virgin polymer in roofing materials by ground car bumper waste. - Evidence of strong adhesion between uncoated mineral fillers and polymers when mixed at relatively high shear in a Gelimat mixer. For example, precipitated calcium carbonate with 70nm particle size has been very successfully processed even at high loading levels. - The successful modelling of the KEX extruder - which although of quite low shear (... 750 sec-1 ) - produces excellent dispersions of fillers in polymers. Exploitation plans are being pursued in each of these areas. It is necessar

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