In this paper,the relationship between the mechanical properties and the crystalline structure of propylene random copolymer ( PPR) /isotactic polypropylene ( iPP) blends modified by a rare earth complex ( β-nucleator) was investigated by means of DSC and XRD. When the dosage of β-nucleator is kept at 0. 05%,it is found that ( 1) the impact strengths of PPR,PPR/iPP( 70 /30,50 /50 and 30 /70 in mass ratio,respectively) blends and
iPP increase from 42. 7,33. 7,14. 5,8. 3 and 5. 1 kJ /m2 to 87. 8,63. 4,29. 3,13. 9 and 8. 2 kJ /m2,respectively,while the tensile strengths all decrease by less than 10%; ( 2) the melting temperature of PPR/iPP ( 70 /30 in mass ratio) blend decreases from 161. 9 ℃ to 149. 8 ℃ and the relative content of β-form crystal increases from 45. 3% to 53. 1%,which reveals a remarkable nucleating promotion to β-form crystal; and ( 3) there exist typical ductile fractures in the impact-fractured sections of the blend,which is verified by the SEM photographs. Moreover,when the dosage of β-nucleator increases to 0. 20%,the melting temperature of the blend and the relative content of β-form crystal respectively reach 159. 8℃ and 45. 1%,and the nucleation to β-form crystal of the blend weakens,thus resulting in a decrease in the impact toughness.