Abstract: For thoroughly analyses of the aging factors affecting on the injection molded parts, the rectangular shell parts with standard tensile sample at the bottom, whose injection mold with ultrasonic assisted vibration system were designed and manufactured. The isotactic polypropylene material was selected in the molding experiments, which were carried out under different processing parameters and ultrasonic vibration actions. And with the molded parts, the neutral salt spray aging experiments were carried out. Meanwhile, by means of wide angle X-ray diffraction, Fourier transform infrared spectrometer analysis, scanning electron microscope and the tensile test, the mechanics property of the parts was evaluated and the relationship between the formation of condensed state structure and anti-aging properties of the samples was characterized. Furthermore, the influences of melt temperature, molding temperature, holding pressure and ultrasonic power on the formation of condensed structure and the anti-aging properties were studied. Results clearly show that the salt spray aging resistance of the parts will be degraded by the rise of melt temperature, while the salt spray aging resistance of the parts will be improved by the rise of molding temperature and packing pressure. Increasing the ultrasonic power may increase the crystallinity inside the parts, but when the ultrasonic power exceeds 200 W, the tensile strength of the parts is greatly reduced. It can be seen that excessively high ultrasonic power is not conducive to the formation of condensed state structure with optimal anti-aging properties inside the parts.

Key words: injection molded part, processing parameter, ultrasonic vibration, condensed state structure, salt spray aging, property test

摘要： 为了对注塑成形制件老化因素进行深入分析，设计制造了带有超声辅助振动系统的注塑模具来成形底部带有标准拉伸试样的矩形壳体制件。选用等规聚丙烯材料进行了不同工艺参数和超声振动作用下的成形试验，并对试验获得的制件进行了中性盐雾老化试验。同时借助X射线衍射、傅里叶变换红外光谱分析、扫描电子显微镜观测及拉伸试验等方法，研究了熔体温度、模具温度、保压压力及超声功率变化对制件内部凝聚态结构的形成与其抗老化性能的影响。研究结果表明，升高熔体温度会使制件的抗盐雾老化性能下降,而提高模具温度和保压压力则可使制件的抗盐雾老化性能提升；增大超声功率虽可使制件内部的结晶度增加，但超声功率超过200 W时，制件的拉伸强度却大幅下降,可见过高的超声功率并不利于制件内部形成具有最佳抗老化性能的凝聚态结构。

关键词: 注塑成形制件, 工艺参数, 超声振动, 凝聚态结构, 盐雾老化, 性能检测