Abstract: Aluminum hydroxide was modified with rare earth complex coupling agent and the performance of the product was compared with those modified with other coupling agents including silane and titanate. Modified with rare earth complex, the activation index increased from zero to 99%，while the oil absorption value falls from 0.4214g to 0.2747g，which indicated that the surface of aluminuet hydroxide was transformed to hydrophobic. Measured by differential thermal analysis, the initial thermal decomposition temperature of aluminum hydroxide was increased to 249 C .the elongation at break of polypropylene (PP) containing rare earth complex modified Al (OH):was 5 .24 times higher than that containing unmodified Al(OH)3，and was 59 .5%higher than that of neat PP. the impact toughness of polypropylene (PP) containing rare earth complex modified Al (OH):was 17. 7% times higher than that containing unmodified Al(OH):，and was 14 .8%higher than that of neat PP. the rare earth complex modification also improved the fire retardant properties of PP.

Key words: rare earth complex coupling agent, aluminum hydroxide, surface modification, polypropylene