AbstractAcrylonitrile–butadiene–styrene (ABS) plastics from computer equipment housings have been reprocessed, some under various conditions of temperatures and shearing rates and others for multiple numbers of cycles. Structural changes in these reprocessed materials were investigated by infrared spectroscopy (FTIR), gel permeation chromatography, and dynamic mechanical thermal analysis. Gas chromatography/mass spectrometry was used to analyze extracts from the ABS plastics. These studies were related to measurements of the mechanical properties of the reprocessed materials, and the fracture surfaces were examined using scanning electron microscopy. It was found that impact strength was much more significantly affected than tensile properties by reprocessing. Within the range of reprocessing parameters studied, temperature had a more significant effect than shear rate on mechanical properties. Significant reductions in impact strength and slight increases in stiffness and strength, particularly following reprocessing at the highest temperature of 270°C and multiple reprocessing, were linked to loss of small molecules (including lubricants), degradation (crosslinking and scission) of the rubber phase, and changes in the morphology seen in the fracture surfaces. POLYM. ENG. SCI., 47:120–130, 2007. © 2007 Society of Plastics Engineers