In this study, nano sized zinc borate powder with a formula of 4ZnO center dot B2O3 center dot H2O was synthesized using 2ZnO center dot 3B(2)O(3)center dot 3.0-3.5H(2)O as a starting chemical which was produced using a wet chemical method. After dissolving 2ZnO center dot 3B(2)O(3)center dot 3.0-3.5H(2)O in an ammonia solution, the clear solution was boiled until a white powder formed. The resultant powder was characterized with XRD, FTIR, TGA and TEM. XRD, FTIR and TGA results proved that the powder was belonged to the 4ZnO center dot B2O3 center dot H2O. Nano composites of 4ZnO center dot B2O3 center dot H2O-polyvinylchloride (PVC) were produced by injection moulding by adding 1 and 5 wt% zinc borate powders into PVC to enhance its flame retardancy. Limiting oxygen index (LOI) of virgin PVC increased from 41% to 47% and 54% for the 1 and 5 wt% zinc borate added PVC, respectively. Nano zinc borate addition into the PVC does not have considerable negative effect on the mechanical properties of zinc borate-PVC composites even at high amounts of 5 wt%. (C) 2011 Elsevier Ltd. All rights reserved.