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Cristiano Ribeiro Santi, Elias Hage Jr., Carlos Alberto Correa, John Vlachopoulos
Torque Viscometry of Molten Polymers and Composites

Appl. Rheol. 19:1 (2009) 13148 (7 pages)

A systematic approach for collecting data from a torque rheometer is described, and the Bousmina et al. model is evaluated for HDPE, LDPE, LLDPE and HDPE/filler composites. The torque rheometer results are in good agreement to capillary and parallel plate viscometer measurements for neat polymers, when the torque values measured are corrected for the temperature rise due to viscous dissipation. For the composites, the torque and capillary results virtually coincide, but the viscosities are lower than those measured with the parallel plate instrument, in oscillatory mode, because the Cox-Merz rule is not valid. Although there are some limitations at high shear rates, due to viscous dissipation, the present work provides a proof and a methodology for the practical utility of torque rheometers for viscosity measurement in highly viscous systems.

Cite this publication as follows:
Santi CR, HageJr E, Correa CA, Vlachopoulos J: Torque Viscometry of Molten Polymers and Composites, Appl. Rheol. 19 (2009) 13148.

Velichko Hristov, John Vlachopoulos
A Study of Entrance Pressure Loss in Filled Polymer Melts

Appl. Rheol. 17:5 (2007) 57191 (9 pages)

The influence of the molecular structure of the polymer matrix and filler loading on the entrance pressure loss of polyethylene/ wood flour composites has been investigated in this research by means of a capillary rheometer equipped with an orifice die. The entry flow of talc- and glass-filled polyethylene composites has been investigated as well. It was found that the entrance pressure loss of wood filled polyethylene composites greatly increased with increasing the wood flour loading. Talc and solid glass spheres also increase the entrance pressure loss, however not as much as wood flour. It was also observed that composites based on narrow molecular weight distribution (MWD) resins exhibited larger entrance pressure loss than the broad MWD and branched polyethylene based ones. It was concluded that measurements of the entrance pressure loss reveal some interesting features of the polymer-filler interactions and could provide significant insights in the processing of highly filled polymer melts.

Cite this publication as follows:
Hristov V, Vlachopoulos J: A Study of Entrance Pressure Loss in Filled Polymer Melts , Appl. Rheol. 17 (2007) 57191.

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