2D-i.r. spectroscopy involving mechanical excitation is employed to study the mechanical relaxation phenomena in a styrene-acrylonitrile/butadiene (ABS) sample, revealing detailed information regarding the molecular segments involved in macroscopic mechanical relaxation. From the temperature dependence of the dynamic signals it is corroborated that in the ABS sample the polybutadiene (PB) rubber relaxes entirely independently from the styrene-acrylonitrile (SAN) matrix, and thus is present as a separate phase in the material. The rapid-scan variation developed to perform 2D-i.r. experiments offers a significantly reduced measurement time in comparison with the step-scan mode of operation. In particular, in relation to research in the polymer field, in which case stress relaxation is expected to occur during the 2D-i.r. experiment, this presents a major advantage.