Effect of acrylonitrile content on the delamination toughness of PC/SAN microlayers

Abstract

The effect of acrylonitrile (AN) content on the adhesion of poly(styrene-co-acrylonitrile) (SAN) to polycarbonate (PC) was examined by measuring the delamination toughness of PC/SAN microlayers in the T-peel test. Experiments were carried out on microlayers with thin SAN layers, to ensure that delamination would occur predominantly by an interfacial mechanism, and with PC layers that were thick enough to prevent the delamination crack from tearing through the PC. Layer thicknesses of approximately 4.5 μm/0.5 μm (PC/SAN) gave satisfactory results. A broad maximum in the interfacial toughness occurred at about 20% AN. When microlayers with thicker SAN layers were tested, only SAN compositions with 15–25% AN crazed. This increased the delamination toughness and greatly exaggerated the maximum at 20% AN. Crazing only occurred if the interfacial toughness of PC-SAN exceeded the SAN crazing condition. When the crazing condition, which increased linearly with AN content, was overlayed with the interfacial toughness, the intersections correctly predicted the AN content for transitions in failure mode.