Thermal and smoke properties of poly(vinyl chloride)/copper-containing layered double hydroxide (MgCuAl-LDH) composites were studied in this article. Highly crystallized LDH with platelet size at micrometer scale was prepared via urea hydrolysis and further intercalated with a variety of anions. X-ray diffraction results indicated an enlargement of basal spacing to 2.54 nm for dodecylsulfonate-intercalated LDH. The effects of LDHs on thermal stability and degradation behavior of PVC were investigated by Congo Red tests and thermogravimetric analysis (TGA). By incorporating 3 wt % LDHs, the thermal stability times of carbonated MgAl-LDH and MgCuAl-LDH/PVC composites were even three and five times of that of neat PVC. The TGA showed an increase of polyene sequences and char residues formed during PVC pyrolysis. MgCuAl-LDH/PVC composites gave the best reduction in maximum density of smoke, i.e., 25% lower than that of MgAl-LDH/PVC composites. However, the organomodification of LDH by anion exchange gave no contribution to improvement of thermal stability of PVC. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 273-281, 2011