Röntgenkleinwinkel‐untersuchungen zur struktur der crazes (fließzonen) in polycarbonat und polymethylmethacrylat

Abstract

AbstractSmall angle X‐ray scattering measurements were made on samples of polycarbonate (PC) and poly(methyl methacrylate) (PMMA) containing crazes. A sharp, well pronounced maximum in the scattering intensity was observed in the direction perpendicular to the draw direction. The distribution of scattered intensity around the draw direction and the effect of contraction of the craze fibrils on the scattering curve, support the suggestion that the observed maximum in intensity arises from interfibrillar interference. Calculated scattering curves for a system of parallel cylinders with a liquid like order are in good qualitative agreement with the observations. The average fibril's diameter a can be determined from the position of the scattering intensity maximum and from the asymptotic behavior of the scattering curve. Very good agreement was obtained between the two methods. No alteration of a with Mw was found for the PMMA samples. For PC it was found that a increased with increasing draw temperature and decreased with increasing draw rate. We can attribute this behavior to the dependence of the yield stress σy on the drawing conditions, because aσy was found to remain constant. This quantity is defined as the fibrillation energy. On the basis of this observation the results are discussed in terms of the “meniscus instability” model of Argon and Salama. A simple explanation of the results can be given by proposing an energy balance during craze growth.