The mechanism of char formation effect of zinc acetylacetonate (Zn(acac)

2

) on acrylonitrile-butadiene-styrene copolymer (ABS) was studied. Thermal gravimetric analysis (TGA) was used to study the mass loss and char yield of ABS composites.

In situ

temperature-dependent Fourier transform infrared spectroscopy (FTIR) was used to characterize the chemical change during thermal decomposition. Roman spectroscopy and scanning electron microscopy (SEM) were applied to characterize the structure and morphology of the char after combustion. Results showed that the presence of Zn(acac)

2

not only slowed down thermal decomposition of the ABS composites

but also increased the charred residue. A more compact and denser char layer with higher graphitization degree was formed for ABS composites with Zn(acac)

2

. To study the char formation mechanism of Zn(acac)

2

on ABS

thermal decomposition was analyzed for the composites of Zn(acac)

2

with PB

PS and SAN

respectively. Also

the chemical structure change was investigated for Zn(acac)

2

during thermal decomposition. Based on these results

it was deduced that the increase of char yield of ABS composites was probably attributed to the interaction between the units of acrylonitrile in ABS and zinc acetate

produced during the thermal decomposition of Zn(acac)

2

. A proposed mechanism for crosslinking and the subsequent char formation was presented.