In this article, the effects of low temperature Ar glow discharge plasma modification on the surface of polypropylene (PP) and polystyrene (PS) plates were characterized by X-ray photoelectron spectroscopy, and the temporal change of the complex viscosity (?*) of PP/PS plates with a sandwich structure were measured by a rotational rheometer. The results showed that the formation of reactive groups on the surface of PP and PS plates was due to the reaction of O2 with some free radicals when exposed to air. In the rheology study, because of the increase of interfacial adhesion strength due to the coupling reaction between the reactive groups at the interface, ?* increased with welding time. There were two distinct stages for the changes of ?* with welding time. In Stage I, ?* increased rapidly and indicated a reaction-controlled kinetics, the apparent reaction kinetics was a first-order reaction; in Stage II, ?* increased slowly and indicated a diffusion-controlled reaction. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012