Elucidating the relationships between polyolefin architecture and mechanical properties

David G Bucknall (Heriot-Watt University, UK)

Polyolefins are the most widely used and exploited plastic globally with approximately 27 lbs of polyethylene produced annually for every person on the planet. Despite its apparent relative simplicity of structure, polyethylene is produced in a wide range of configurations, i.e. HDPE, LDPE, UHMWPE, etc, and through which properties can be varied quite considerably. The mechanical properties of polymers can be understood using continuum methods, such as spring and dashpot models. Unfortunately, these models are fatally flawed for a number of reasons. Firstly, they are not predictive, i.e. they only match observed behaviour, secondly, at high deformation rates, they are not able to explain the observed behaviour, and thirdly, there is no direct way to correlate these models to the chemical structure. Consequently there is no easy way to pre-determine which specific PE configuration to synthesis to meet property requirements. We have been exploiting both ballistic Taylor impact experiments in addition to in-situ X-ray scattering deformation studies of PEs to try to establish correlations between properties, morphology and ultimately chemical structure. This talk will discuss these studies.

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