Member Control Panel
Microscale Polymer Processing
| By Dr. Suneel Kunamaneni Introduction The Polymer IRC (Interdisciplinary Research Centre) at the Universities of Leeds, Sheffield, Durham and Bradford in conjunction with the Universities of Cambridge and Oxford has, over the last 10 years, successfully run a world-leading project, the “Microscale Polymer Processing” consortium (µPP). The aim of µPP was to develop an understanding of how molecular parameters affect the processing of industrial polymers. This was achieved by the unique idea of synthesising small quantities of polymers with known molecular parameters in sufficient quantities of a few grams, to allow them to be processed using specially designed rigs. Ultimately, the aim was to follow the processing path of well characterised polymers from synthesis, through processing and property evaluation, combined with the parallel development of a mathematical and computational modelling protocol. Please visit www.mupp2.com for more details. In spite of the increased sophistication of polymeric materials, now designed with many molecular parameters in mind, the choice of resin is still more an art than a science. Requirements often specify no more than the “melt flow index”, a number which can have little or no relevance to the actual process performance of the plastic. The missing information is the set of rules that connect the molecular structure of a polymer to its process performance in a predictive way, expressed in terms that SME converters can handle. This leads to huge wastage in down-time, poor supply-chain and consequent lack of competitiveness. There is therefore a huge opportunity to supply this sector with latest tools based on new physics generated within the µPP consortium. The many potential benefits of these tools include:
In the following sections we describe some of these tools. FlowSolve – theory in application FlowSolve is an advanced Computational Fluid Dynamics (CFD) software, developed at the University of Leeds, for the analysis of polymer processing and hosts a library of molecular polymer melt models. FlowSolve is capable of visually predicting process features of plastic melts that depend on their specific molecular structure. There exists a fundamental lack of quantitative and qualitative knowledge with regards to the relationships between machine design, total process operation and polymer flow. This knowledge gap has been identified as a major barrier to the advancement of polymer processing. FlowSolve will significantly strengthen the knowledge-base available to the polymer industries, enabling the realisation of new and optimised materials with enhanced properties and functionality, greater process efficiency and energy reductions. REPTATE – analysing rheology made easy Rheology, which is the study of fluid flow, is a fundamental tool in polymer research and is a central science that can be applied successfully to material systems as seemingly dissimilar as tomato ketchup and paints, and the use of rheometric instrumentation in development and quality control is well established in the plastics industry. As a comprehensive materials and process design tool, however, the traditional rheometer is of limited use. We have therefore developed the REPTATE (Rheology of Entangled Polymers, Toolkit for Analysis of Theory and Experiments) software which is uniquely suited to understand the molecular structure of polymers using advanced physics based theories. It has potential applications in understanding batch to batch variability, reducing operator variability, increasing efficiency and designing new polymers for a given target application. The main idea of REPTATE is to create a platform which makes comparing theory and experiment much easier than ever before, in order to fast track development of new materials and optimize existing production processes. Please visit www.reptate.com for further details. BoB and REACT – nothing is impossible The processing properties of plastics are governed by the reaction chemistry used to make the material. The reaction chemistry controls the structure (branching) of polymer chains. Understanding the links between the chemistry and final properties is key to designing tailored polymer materials. We have used this idea to develop the Branch on Branch (BoB) software tool. This prescription has been used successfully for modeling the properties of both conventional LDPEs and metallocene catalyzed polyethylene. A separately developed reaction chemistry software REACT is used to produce the input for the BoB tool. Product development with this tool can help move metallocene polymers from specialty applications focus into the arena of commodity markets and applications. In making this move, economic considerations and manufacturing efficiencies become important drivers of technology development. For further information on BoB, please visit http://sourceforge.net/projects/bob-rheology/ . Both BoB and REACT are also embedded in the REPTATE platform, albeit with few less features. Conclusions The microscale polymer processing project has radically transformed understanding of polymer rheology and processing, from a phenomenological based approach to that based on physics, which is both descriptive and predictive. We have used the science to create novel polymers, both unfilled and filled, that extends the range of processability, into areas previously unobtainable and expect these developments to grow in the future. The software tools enable connecting in-house process knowledge (knowing how to make molecular systems) with application properties (knowing which molecular systems have certain properties). These tools can give plastics producers and processors a competitive edge that is essential in today’s environment. Dr. SUNEEL KUNAMANENI School of Process, Environmental and Materials Engineering (SPEME) University of Leeds Tel: +44 (0) 113 343 8592 Fax: +44 (0) 113 343 2384 Email: S.Kunamaneni@leeds.ac.uk Web: www.engineering.leeds.ac.uk/speme/ |
