Poly(acrylonitrile-butadiene-styrene)(ABS) composites containing (i) hindered amine light stabilizer(HALS);(ii) nano-scale rutile titanium dioxide (n-TiO2); and (iii) both HALS and n-TiO2 were prepared by meltblending process.To prevent agglomeration of nanoparticles

the surface of the n-TiO2 nanoparticles were modified to ensure a good dispersion.The pure ABS and ABS composite samples were under accelerated aging test for 28 days with a laboratory xenon arc lamp (GB/T16422.2-1999)

and their ageing resistant properties were investigated by Izod unnotched impact

Izod notched impact properties measurements and fracture surface analysis.The morphologies of the unnotched impact fractured surface of pure ABS and ABS composites samples at different irradiation time were characterized by scanning electron microscope (SEM) and optical microscope.According to the SEM photos of brittle fracture (liquid nitrogen immersion) and impact fracture

it can be seen that cavities and knobs on fracture surface were formed by rupture of rubber phases dispersed in ABS when it was under lateral impact.On the other hand

the n-TiO2 less than 100 nm dispersed uniformly in ABS with no evident large agglomerated particles was helpful to its function as ultraviolet screen agents.With the UV shielding capability of nano-scale rutile TiO2 and HALS

the ageing resistance of ABS samples was improved.Moreover

the ageing resistance of ABS/n-TiO2/HALS composites samples is better than that of ABS/n-TiO2 and ABS/HALS composites samples

suggesting a synergistic effect between HALS and n-TiO2.After 28 days exposure to xenon arc lamp the retained percentage of Izod unnotched impact strength of ABS/2.0 wt% n-TiO2/0.6 wt% HALS composites samples was 47.9%

which was more than 2.5 times as high as that of pure ABS.At the same time the retained percentage of unnotched impact strength of ABS/0.6 wt% HALS composites samples was 29.2% after 28 days exposure to xenon arc lamp

which is attributed to diffusion n-controlled oxidation.The retained percentage of Izod unnotched impact strength of ABS/0.5 wt% n-TiO2 composites was only 23.8% after 28 days exposure to xenon arc lamp.The presence of n-TiO2 could confine degradation in a thin region close to the exposed surface.It is obvious that n-TiO2 could not only shield the ultraviolet irradiated on ABS but also prevent impurity and HALS in ABS from being destroyed by ultraviolet.ABS/05 wt% n-TiO2/HALS composite samples had a higher unnotched impact strength

which was increased by 15.3% compared to pure ABS samples

and the tougheness of ABS was increased to a great extent.By impact fracture surface morphology analysis it was found that for unstabilized ABS specimens

there was a bigger smooth zone on fracture surface with very little impact strength retained only after four days laboratory weathering exposures.There is a correlative relation between proportion of smooth zone and retained percentage of unnotched impact strength of pure ABS samples after accelerated aging.The whole unnotched impact fractures surface of exposed and unexposed ABS/2.0 wt% n-TiO2/0.6 wt% HALS composites were white or gray

just as unnotched impact section of unexposed pure ABS

and there were few rubber particles and cavitation left by the pull-off of them exposed on the section.