Effect of Chemical Degradation and Formulation Stability on Viscoelastic Relaxation Processes at University of Surrey
Job Description
Current accelerated stress relaxation tests indirectly show how a polymer network rearranges (viscoelastic considerations) to reduce the applied stress (thermodynamic considerations). During thermal acceleration however, many different processes occur in addition to the viscoelastic relaxation.
The rate of loss of formulation additives is often assumed to scale linearly with temperature (diffusion / out gassing / leaching), however, this has never been measured. A combination of experimentation and modelling are required to provide a modified age aware prediction.
Certain accelerated ageing test regimes study the chemical ageing of a network by thermo-oxidative degradation. It is known that a combination of polymer scission and / or cross-linking occurs to alter the state of the polymeric network (in addition to chemical modification). It is generally assumed that elastomeric materials stiffen (due to loss of viscous character) and thus the rate of stress relaxation diminishes however, this is not measured. It is therefore advantageous to understand how chemical degradation also directly affects the viscous relaxation process. This would require a combination of experimentation, modelling and also an understanding of formulation changes (i.e. leaching of additives, processing variables, additives, plasticisers) so that the complex behaviour exhibited by a dynamic system evolves due to the combination of physical, viscoelastic and chemical processes which occur through life. It is NOT fully understood how fillers (e.g. Silica, Boron, etc) alter these ageing processes. This is particularly so with highly filled soft AM materials where potential changes (e.g. hydrolysis, physical rearrangement) at the boron/binder phase could alter relaxation rates (and performance) in a complex way which is not fully understood.
Supervisors: Dr David Watson, Dr Jasmine Bone
Find out about the Centre for Engineering Materials.
This project is open to UK students starting in October 2022.
Entry requirements
Open to UK nationals only. Starting in October 2024.
You will need to meet the minimum entry requirements for our PhD programme. Candidates must have a First or Upper second in a physical sciences subject.
How to apply
If you are interested in this project, please contact Noelle Hartley in the first instance by emailing n.hartley@surrey.ac.uk. A formal application will also need to be submitted the Engineering Materials PhD programme page on the “Apply” tab. Please state clearly the studentship project that you would like to apply for and the name of your intended supervisor.
Funding
Fully funded for UK fees. Stipend of £18,622 (subject to review) and University of Surrey fees met for duration of studentship. Funded by the University of Surrey and AWE.
Closing date for applications
Friday 1 July 2024
Application enquiries
For application enquiries, please contact Noelle Hartley (n.hartley@surrey.ac.uk).
Studentship ref
PGR-2122-120
