Mechanical property, thermal property and crystal structure of isotactic polypropylene samples prepared by vibration injection molding

A self-designed pressure vibration injection device was used to study the effect of vibration frequency and vibration pressure on tensile strength and impact strength of iPP F401 vibration injection molding samples. Furthermore, vicat softening temperature, WAXD measurements and polarized microscopic observation were conducted. According to the results, tensile strength and impact strength increase with increasing vibration frequency and vibration pressure. The maximum increment of tensile strength is 26.1%. Under certain process conditions, there is a transition of the impact strength, whose maximum increment is 85%. The vicat softening temperatures have a significant increase of 6 similar to 8 degrees C for the samples obtained at high vibration frequencies compared with that of static samples. According to pole figures, a-PP of vibration samples orientates much stronger than that of static samples. PM micrograghs show that vibration changes the crystal structure of samples and enhances their orientation.