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The mechanical behavior of polycarbonate (PC) coextruded as microlayers with a brittle polymer, either poly(styrene-co-acrylonitrile) (SAN) or poly(methy1 methacrylate) (PMMA), was examined. Adhesion between layers was measured with the T-peel method. The much higher interfacial toughness of PCPMMA microlayers compared to PC/SAN was attributed to partial miscibility. Comparison of the microdeformation behavior of 32-layer PC/SAN and PCPMMA microlayers revealed that very good adhesion between PC and PMMA constrained yielding of the PC. This was seen in the tensile stress-strain curves as a broader stress drop at the yield point and a lower fracture strain. Decreasing the layer thickness by increasing the number of layers enhanced the ductility of both PC/SAN and PCPMMA microlayers. A PC/PMMA microlayer with 4096 layers and a composition of 80 % PC achieved the ballistic performance of polycarbonate.

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