A series of blends of poly(vinyl chloride) (PVC) with (1) poly(methyl methacrylate) (PMMA) or (2) polyoxymethylene (POM), with lithium acetate as a stabilizing agent, was investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), either alone or coupled with Fourier transform infrared (FTIR) spectroscopy. It was found that lithium acetate has a significant effect on the thermal properties of blends under investigation. It causes the initial decomposition temperatures to increase by about 60-150 degrees C for PVC-POM blends, a substantial suppression of the volatile products evolution for PVC/PMMA blends, and an improvement in the surface morphology for both polymer systems by lowering the degree of roughness. The origin of these effects was discussed by analysis of the intermolecular complexation between metal salt and PVC structural arrangements in the blends. Such interactions may lead to the formation of long-range, directional-specific structural regularities, which in turn thermally stabilize the whole system (strong interactions model).