Application of the MLD ' toy' model to extensional flows of broadly polydisperse linear polymers: Part II. Comparison with experimental data

摘要

The new diluted stretch tube polydisperse MLD " toy" model developed in Part I is used to simulate experimental data for a " spiked" and " unspiked" polydisperse polystyrene melt with a broad molecular weight distribution in transient uniaxial, planar and bi-axial extensional flows [1-3]. The new model is in good agreement with experimental data sets in transient stretching flows whereas the original " na?ve" polydisperse MLD " toy" model without incorporation of the new physics completely fails to capture salient features of stretching flows, such as strain hardening, of these broadly polydisperse systems. Quantitative analysis of the apparent distinctions in material response between different types of transient extensional flow is performed in terms of the new polydisperse MLD diluted stretch tube model. Results of this analysis quantitatively explain why uniaxial extension is the most strain hardening and bi-axial extension is the least strain hardening extensional flow thereby resolving this long standing and previously enigmatic issue.