CHARACTERISATION OF POLYOLEFINS USED FOR FOAMING VIA NON-LINEAR RHEOLOGICAL METHODS

摘要

The appropriate characterisation of polymers suitable for foaming is still one of the main challenges faced by polyolefin producers. The understanding of the links between molecular structural properties and end performance requires the development and use of sophisticated analytical methods. Within this work, a series of different industrial polypropylene and polyethylene based systems will be analysed with respect to their Theological behaviour under both shear and extensional flows. The molecular structural characterisation of these systems will be done responding to novel, non-linear Theological parameters, which give both a semi-qualitative and semi-quantitative description of the molecular topology. The analysis will include Large Amplitude Oscillatory Shear (LAOS), uniaxial extensional flow and Rheotens measurements. It will be shown that, regardless of the technique used, all non-linear Theological parameters are sensitive to both amount and type of long chain branching, in both polyethylene and polypropylene based materials.