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Experimental methods in polymer melt rheology
Author(s) -
Meissner Joachin
Publication year - 1993
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19930680111
Subject(s) - rheometer , materials science , rheology , composite material , polystyrene , simple shear , shear rate , shear flow , strain rate , polymer , elongation , pure shear , anisotropy , shear stress , shear (geology) , perpendicular , mechanics , ultimate tensile strength , optics , physics , geometry , mathematics
Experimental developments in different areas of polymer melt rheology and recent results are reviewed: Shear oscillations were performed with mixtures of polyisobutylenes (PIB) of relatively small molecular mass distributions and with blends of polystyrene (PS) and polymethylmethacrylate (PMMA). For the latter, the interfacial tension between the melts of PS and PMMA can be derived from the results. ‐ In constant shear rate flow, the measurement of the first normal stress difference N 1 in a commercial cone‐and‐plate rotational rheometer is simple if the test temperature is kept extremely constant. By a further modification a partial integral of the pressure distribution is measured from which the second normal stress difference N 2 can be determined. ‐ The molecular orientation in shear flow results in a rheological anisotropy that can be studied in a parallel‐plate shear rheometer in which the polymer melt sample can arbitrarily be sheared in two perpendicular directions. ‐ For melt elongation by rotary clamps constant, arbitrary ratios of the strain rate components can be applied. Planar elongations of the PIB samples indicate an influence of the width of the molecular mass distribution. More general elongations with a change of the strain rate ratio during the test are of especial interest as is documented by the comparison of the resulting stresses with predictions from different network theories. ‐ In a rheometer for simple elongation at 170°C, recovery after melt extension of the PS/PMMA blends reveals a value of the interfacial tension equal to the one obtained from shear oscillations.