Plastic rod as a promising feed material for enhanced performance of ultrasonic plasticization microinjection molding: Plasticization rate, mechanical and thermal properties

A polymer plasticization rate measurement method is proposed for ultrasonic plasticization microinjection molding. The effect of ultrasonic amplitude on the plasticization rate of polypropylene (PP) rods was comprehensively investigated, and the mechanical and thermal properties of PP rods were studied using tensile tests, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Results show that the plasticization rate of PP rods increased from 67.25 mg/s to 192.41 mg/s with increase of ultrasonic amplitude, an increase of 186%. The mechanical properties of the PP samples remained stable under different ultrasonic amplitudes, with tensile strength around 21 MPa and elongation at break about 21%. DSC and TGA results showed that PP samples exhibit improved thermal properties after ultrasonic plasticization compared with pure PP. The melting point of the PP sample decreased from 171.7 °C to 164.0 °C and the crystallinity increased from 26.1% to 38.7%. The temperatures corresponding to 1% and 5% weight loss of PP increased from 283.63 °C to 350.30 °C without ultrasonic amplitude to 393.70 °C and 420.13 °C, respectively. The studies have great significance to further understand the influence of ultrasonic plasticization process parameters on the plasticization rate and material properties of polymers