A custommade dynamic injection molding machine was adopted to obtain PP specimens via changing the vibration frequency (5～25 MPa) and vibration stress (10～18 MPa).The specimens were characterized by tensile tests

notched Izod impact tests

dynamic mechanics analysis and creep measurements under a tensile load of 12 kg.For specimens prepared under a vibration frequency of 10 Hz their 24 h creep strain decreased from 7.4% to 4.5% with an increase of vibration stress from 10 MPa to 18 MPa.While for specimens prepared under a vibration stress of 12 MPa their 24 h creep strain increased with vibration frequency first

and after 10 Hz its variation became very slow.It was also found for these specimens that the Izod impact strength increased from 3.2 kJ/m2 to 4.2 kJ/m2

when the vibration stress changes from 10 MPa to 18 MPa

and

at the same time

the Izod impact strength decreased with increasing vibration frequency first and showed a minimum around 20 Hz.The influence of processing conditions on tensile elongation and dynamic mechanical properties were also observed.All the results indicated that within the experimental conditions used in this work increasing the vibration stress and decreasing the vibration frequency during processing could improve the long-term mechanical performance and impact ductility of PP specimens.