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A calibration technique to evaluate the power‐law parameters of polymer melts using a torque‐rheometer
Author(s) -
Marquez Alfredo,
Quijano Jafet,
Gaulin Marc
Publication year - 1996
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10655
Subject(s) - rheometer , torque , calibration , materials science , mechanics , logarithm , rheometry , power law , consistency (knowledge bases) , work (physics) , shear rate , physics , mathematics , rheology , thermodynamics , composite material , mathematical analysis , statistics , geometry
In this work we develop an empirical method to calibrate the measuring head of a torque‐rheometer to obtain the power‐law parameters of polymer melts. This method is based on a similar analysis developed by Lee and Purdon. However, in this work, only one geometrical parameter, with well‐defined physical limits, is needed for calibration, instead of the two arbitrary parameters proposed by the previous authors. Moreover, this parameter is closely related to the ordinate of the logarithmic relationship between the torque ( M T ) and the angular velocity ( S 1 ), obtained from the torque‐rheometer data. This allows us to define a calibration function for this parameter, which is used to evaluate the consistency index ( m ) of the melt. On the other hand, experimental results confirm the equivalence between the slope of the logarithmic values of torque and angular velocity obtained from the torque‐rheometer data and those of shear stress vs. shear rate obtained from capillary rheometry. This further highlights the feasibility of evaluating the melt flow index ( n ) and the consistency index ( m ) from the torque‐rheometer data.