University of Birmingham > Talks@bham > Applied Mathematics Seminar Series > Modelling polymer crystallisation under flow: from molecular shape to flow properties and crystallisation.

Modelling polymer crystallisation under flow: from molecular shape to flow properties and crystallisation.

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  • UserRichard Graham (University of Nottingham)
  • ClockMonday 25 November 2013, 14:00-15:00
  • HouseArts Lecture Room 4.

If you have a question about this talk, please contact Alexandra Tzella.

*This talk will be particularly accessible to year 4 undergraduates.*

Polymers are extremely long molecules, formed by joining together many simpler molecules into a chain. Due to their size, polymer chains move much more slowly than simple molecules. They are sufficiently slow that flow can stretch, unravel and deform individual chains. This molecular deformation leads to richly non-linear and strongly non-Newtonian flow properties. Furthermore, molecular deformation drastically increases the rate of crystallisation in polymers and changes the resulting crystal structures. By distorting the configuration of polymer chains, flow breaks down the kinetic barriers to crystallisation and directs the resulting crystallisation. These effects are of central importance to the polymer industry as crystallisation determines virtually all of the useful properties of polymer products.

The field of molecular rheology attempts to understand and predict flow properties from models of how polymers move. However, modelling polymer crystallisation is extremely challenging due to the huge spread in relevant lengthscales and timescales. Furthermore, the most pronounced crystallisation effects are seen at low undercooling. In this temperature regime the spontaneous formation of small crystals (a process known as nucleation) from which bulk crystallisation occurs is extremely slow. This makes crystallisation especially difficult to simulate because the nucleation dynamics are controlled by extremely rare activated crossing of the nucleation barrier.

We have recently been using a highly coarse-grained simulation algorithm for polymer nucleation. This has provided some encouraging comparisons with experiments. Nevertheless, an extended multiscale approach will be needed to simultaneously include the correct molecular physics, while also producing models that are sufficiently tractable for use in computational modelling of polymer processing. I will summarise current results and discuss methods of increasing the speed of barrier crossing simulations, along with techniques to map simulation algorithms on to non-stochastic models. Finally, I will also highlight some possible future methods to increase the physical detail of the underlying polymer nucleation model.

This talk is part of the Applied Mathematics Seminar Series series.

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