the polished PVC-Ca50 surface is larger than that of the polished PVC-Ca0 surface, significantly for Lewis base component. Thus, itcan be concluded there exists little CaCO3 on the surface of PVC plastic, and CaCO3 will be exposed through polishing.In the case of DnOP, the difference in surface free energy between both the polished and original surface of PVC-DP0 andthat of PVC resin may be due to the effects of other additives such asdibutyl phthalate, which reduce the surface free energy. The change between the original and polished surface of PVC-DP30 indicatesthat DnOP tends to be gathered on the surface of plastic and thusde creases the surface free energy.Owing to the “surface enrichment” effects, the surface of plastic does not exhibit the true performance of polymer resin and addi-tives. Such additive as CaCO3 or DnOP will increase or decrease the surface free energy of plastic. Moreover, the original surface of plastic will be destroyed during the process of crushing or shredding,and thus the effects of additives on surface properties of plastic should be investigated for plastic flotation.