SMALL-ANGLE X-RAY-SCATTERING ANALYSIS OF CRAZING IN RUBBER-TOUGHENED POLYMERS - INFLUENCE OF PARTICLE DEFORMATION

Recently, methods have been developed to characterise the relative amo unts of crazing and non-crazing processes which occur in rubber toughe ned glassy polymers, using the invariant obtained from small angle X-r ay scattering (SAXS) analysis. In this approach, however, the influenc e of the deformation of the rubber particles has previously been ignor ed. In this paper we explore how deformation of a three layer core-she ll rubber particle affects such analysis. It is shown that, for a subm icron rubber particle system, the form factor makes a significant cont ribution to the SAXS pattern, and the intensity of this scattering inc reases as the concentration of rubber particles increases. The details of such form factor scattering are frequently inaccessible, as the sc attering occurs at very low angles. However, various extrapolated form s for this low q scattering have previously been assumed in order to c alculate the amount of crazing by suitable subtraction of it from the experimental data to yield the appropriate invariant. Since the form f actor may change during deformation, as the particles change shape and internal debonding or cavitation may occur, subtracting the scatterin g from the undeformed form factor may or may not be an adequate approx imation. This paper tests the validity oi the approximation. It is sho wn that, for our particular system, the length scale of the internal m orphology of the rubber particles is comparatively large compared with the size of the crazes, and the effect of the particle deformation is indeed fairly minor. However, it is clear that with other systems, a changing form factor may overlap significantly with the peak due to cr azing. This effect will then become significant and must be taken into account. (C) 1997 Elsevier Science Ltd.