Mechanical behavior of polymer microlayers

The mechanical behavior of polycarbonate (PC) coextruded as microlayers wit h a brittle polymer, either poly(styrene-co-acrylonitrile) (SAN) or poly(me thyl methacrylate) (PMMA), was examined. Adhesion between layers was measur ed with the T-peel method. The much higher interfacial toughness of PC/PMMA microlayers compared to PC/SAN was attributed to partial miscibility. Comp arison of the microdeformation behavior of 32-layer PC/SAN and PC/PMMA micr olayers revealed that very good adhesion between PC and PMMA constrained yi elding of the PC. This was seen in the tensile stress-strain curves as a br oader stress drop at the yield point and a lower fracture strain. Decreasin g the layer thickness by increasing the number of layers enhanced the ducti lity of both PC/SAN and PC/PMMA microlayers. A PC/PMMA microlayer with 4096 layers and a composition of 80 % PC achieved the ballistic performance of polycarbonate.