To commercially produce consumer products using engineering polymers, it is very important to control the physical properties of the material. However, quality control of the material is not easy because of many reasons such as cost reduction, cleaning issues, the use of scraps, etc. In many cases, even a small amount of foreign polymers can lead to product failures; however, analyzing such foreign polymers is difficult by using conventional analytical techniques. This article introduces a methodology to evaluate the durability of acrylonitrile-butadiene-styrene copolymers containing foreign polymers by using fracture mechanism maps (FMMs). In addition, the importance of the ductile-to-brittle transition temperature (DBTT) as a quantitative tool is discussed. In this article, the measurement of DBTT was proposed as a direct tool of characterizing polymer blends with similar chemical structure, and the concept of a FMM was applied as a qualitative tool to initiate the detailed investigation of fractures, as well as a quality control tool to sustain the fracture toughness of the final products. POLYM. ENG. SCI., 54:2791-2798, 2014. (c) 2013 Society of Plastics Engineers