High-throughput measurements of viscoelastic properties using surface indentation
Peter M. Johnson, Christopher M. Stafford
Relaxation processes in viscous liquids and glasses have been studied extensively, but the underlying causes of glassy behavior in polymeric systems remains as a major unsolved area of condensed matter physics. These processes are critical in the development of polymers for constant or cyclical load applications, where relaxation processes can lead to permanent deformation or the eventual failure of the sample. Experiments to measure these properties either use long time scale experiments or time-temperature superposition to determine mechanical responses over the required application time. Time-temperature superposition is difficult to implement in thermorheologically complex formulations, involving new models or unknown shift factors. In these cases, a viscoelastic analysis of the system is required to calculate the shift factors and the resulting time-shifted creep compliance curve. This issue commonly arises in polymer blends and composite materials which may have viscoelastic responses that occur from multiple effects in distinct time domains. This complexity is caused by interfacial regions, blend composition, and filler characteristics; these effects contribute to changes in creep compliance and other mechanical properties. In this work, we demonstrate a simple, high-throughput method to measure creep compliance of polymer films using an array of independent spherical indentations. This system can be easily adapted to analyze combinatorial libraries with composition or temperature gradients.
and Stafford, C.
High-throughput measurements of viscoelastic properties using surface indentation, 32nd Annual Meeting of the Adhesion Society, Savannah, GA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=901366
(Accessed September 23, 2023)