The effect of chlorinated polyethylene (CPE) content and test temperature on the notched Izod impact strength and brittle-ductile transition behaviors for polyvinylchloride (PVC)/CPE blends and PVC/CPE/nano-CaCO3 ternary composites is studied. The CPE content and the test temperature regions are from 0-50 phr and 243-363 K, respectively. It is found that the optimum nano-CaCO3 content is 15 phr for PVC/CPE/nano-CaCO3 ternary composites. For both PVC/CPE blends and PVC/CPE/nano-CaCO3 ternary composites, the impact strength is improved remarkably when the CPE content or test temperature is higher than the critical value, that is, brittle-ductile transition content (C-BD) or brittle-ductile transition temperature (T-BD). The T-BD is closely related to the CPE content, the higher the CPE content, the lower the T-BD. The temperature dependence of impact strength for PVC/CPE blends and PVC/CPE/nano-CaCO3 ternary composites can be well simulated with a logistic fitting model, and the simulation results can be illustrated with the percolation model proposed by Wu and Jiang. DMA results reveal that both PVC and CPE can affect the T-BD of PVC/CPE blends and PVC/CPE/nano-CaCO3 composites. When the CPE content is enough (20 phr), the CPE is more important than PVC for determining the T-BD of PVC/CPE blends and PVC/CPE/nano-CaCO3 composites. Scanning electron microscopy (SEM) observations reveal that the impact fractured mechanism can change from brittle to ductile with increasing test temperature for these PVC systems. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1833-1842, 2012