Berlin 2008 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 29: Polymerphysics I
CPP 29.11: Vortrag
Donnerstag, 28. Februar 2008, 12:15–12:30, C 130
The relation between craze structure and molecular weight in PS as revealed by μSAXS experiments — •Nikolaos E. Zafeiropoulos1, Richard J. Davies2, and Manfred Stamm1 — 1Leibniz Institut für Polymerforschung Dresden, Hohe strasse 6, 01069 Dresden — 2European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
The phenomenon of crazing in polymers has received considerable attention in the past as it plays a pivotal role in determining the performance of polymers under load. One aspect of particular interest has been the interconnection between molecular structure, craze characteristics and macromechanical properties. It is generally accepted that the mean craze fibril diameter, the mean craze fibril spacing and the orientation of the craze fibril with respect to the tensile load direction control the craze stability. The fibril volume fraction is independent of molecular weight (MW) under test conditions at temperatures significantly below the glass transition temperature. In addition, little changes in crazing are expected for MWs above the critical molecular weight of entanglement. Three different grades of polystyrene (PS) with different molecular weights have been systematically investigated in situ with synchrotron radiation microfocus SAXS. The results suggest that there are different mechanisms operating in PS samples with low and very high molecular weights, compared to those of medium-high molecular weight. Previously it was thought that, above the critical molecular weight of entanglement, the effect of molecular weight on PS's mechanical behaviour at room temperature was negligible.