Published by the The Society of Rheology Articles you may be interested inStrain hardening of molten thermoplastic polymers reinforced with poly(tetrafluoroethylene) nanofibers J. Rheol. 58, 589 (2014); 10.1122/1.4867389 Extensional rheology of shear-thickening fumed silica nanoparticles dispersed in an aqueous polyethylene oxide solution J. Rheol. 58, 411 (2014); 10.1122/1.4864620 Solution and melt viscoelastic properties of controlled microstructure poly(lactide) AbstractThere have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers. V C 2015 The Society of Rheology.

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Artificial turf surfaces with an integrated shockpad layer are increasing in use, partially due to the introduction of new non-styrene-butadiene rubber infills, which require a shockpad for managing the energy absorption properties of the surface. Selection of appropriate shockpad materials for football pitches is guided by the performance requirements outlined in the FIFA Quality Concept for Artificial Turf [1] manual. Olefinic foams were screened for their performance as shockpads using lab tests in compression along with FIFA Quality Concept (FCQ) tests, both on the foams and on an artificial turf system. Stress response, energy restitution, cyclic loading endurance and creep resistance were generally found to increase with increasing foam density and not be influenced by crosslinking. Foam density was established as the key design variable. The low density foams did not fulfill the FQC performance requirements. At a higher foam density, the nature of the resin played a significant role; elastomeric foams outperforming plastomeric foams by allowing for thinner shockpads at similar energy absorption performance. In addition, FQC test results showed how a welldesigned shockpad could help maintain a uniform performance across the artificial turf surface, overruling the effect of infill height variations caused by players on the field.

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