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Polymers

Modelling of polymer flow drives cheaper product development in the chemical industry

Underpinning research 
All plastics contain polymers, which are long, string-like molecules consisting of many chemical units joined together. The addition of just a few branches to a plastic’s molecular structure (typically one branch every thousand carbons) drastically affects the flow behaviour of the plastic resin in the molten state. Industry exploits this phenomenon to aid the processing of polymer resins, for example by manipulating branches to improve the stability of a polymer melt in the elongational flow encountered in manufacturing processes such as film-blowing. 

The Polymers and Industrial Mathematics group at the University of Leeds has more than ten years of research experience in branched-polymer dynamics, rheology (study of flow and deformation) and polymer-reaction modelling. 

At the heart of the Group’s research is experimental and theoretical investigation into the dynamics of custom-made model polymer architectures, using rheology and complementary tools such as neutron scattering. This multidisciplinary approach is exemplified in a 1999 paper, the first to combine theory, experimental rheology and scattering to study dynamics of melts of simple branched polymers. Researchers were able to show a relationship between molecular shape and the rheological properties for H-shaped polymers.

Summary of the impact 
The Leeds Polymers and Industrial Mathematics (PIM) research group, in projects involving numerous industrial partners, has developed a constitutive equation to model the flow properties of molten-branched polymers. The so-called “multi-mode pom-pom” model is now incorporated in industry-standard software, including the market-leading commercial flow-simulation package (ANSYS). Additionally, software tools developed by PIM allow chemical companies to design in silico branched polymers with specific properties without the substantial costs of trial-and-error development: the user base for this software includes at least four of the top twelve global chemical companies. Use of the software has contributed to the characterisation and optimisation of products with an estimated annual turnover up to €1B, and to the direct employment of specialist research staff.