For the past 40 years bisphenol A polycarbonate has been the industry standard for lightweight transparent armor protection. More recently, researchers at the Shell Chemical Company developed a co-polyester derived from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), 1,3-propanediol (PDO), and dimethyl terephthalate (DMT). By varying the percent incorporation of the monomers, the thermal/mechanical properties of this copolyterephthalate are tunable. Shell found that interesting impact properties arose from the material when 40 mol% CBDO was incorporated into the polymer. This material displayed a notched Izod value of 1070 J/m while maintaining T, near 100 degrees C. The work discussed here focuses on the mechanical, impact, and ballistic characterizations of this material. Tensile, notched lzod, and .22 FSP V50 data are reported. This new material shows improvement over bisphenol A polycarbonate in both notched Izod as well as ballistic impact values. (c) 2006 Elsevier Ltd. All rights reserved.