Study On Morphology And Properties Of Polypropylene Via Vibration Injection Molding Affected By Mold Temperature Field

Lately, plastic melt vibration technology has been widely studied as an effective way to morphology controlling. In this article, former vibration injection molding devices have been improved also accurate thermal controllable sample mold is designed in the research to systematically study the different vibration effect to the sample performance and structure under high mold temperature condition, and received scientific theory results.The main achievements are as below:1. Almost the static injection IPP sample's impact strengths are lower than the vibrated ones under the same mold temperature, and the higher-mold-temperature samples' impact strength increment is bigger than the lower-mold-temperature ones' while the vibration frequency increases. Increase of the vibration frequency is good for the boost of the impact strength. With high vibration frequency condition, the impact strength increment under 135℃mold temperature and 145℃temperature are respectively 16.5% and 21.7%, while with high vibration pressure condition, the impact strength increment are respectively 13% and 18.1%, it's a remarkable leap. With vibration injection compaction, IPP's break elongation rate changes notably. When vibration frequency is low, break elongation rate drops, and sample show poor tough and brittle performance. While the vibration frequency increases, IPP's break elongation rate will exceed the static injection ones'.2. Samples' tensile strength drop when mold temperature increases, from 60℃to 145℃mold temperature, tensile strength drops 7%, and break elongation rate drops 52.8%. It can be explained as the higher mold temperature motivate the molecular to form crystal structure and high crystallization percentage makes the brittle sample and poor ductibility.3. Sample withβnucleator is also studied and found shear force won't affect the nucleation, however, shear will constrain the generation ofβform crystal. In the sample with low content ofβnuleator,βform crystal is mainly induced by shear force, nucleator baffled the generation ofαrow-nucleus, consequently reduced row-nucleus inducedβcrystal.4. PLM shows vibration field result in the melt flow direction orientation of sphere crystal and the sphere size reduction. WAXD shows high melt temperature, high mold temperature and high pressure vibration condition is propitious to the formation ofγcrystal, in this experiment the highest contain ofγcrystal reaches 12.3%. The content ofβcrystal is relative to the processing temperature. Low temperature injection result in low content ofβcrystal, however, high temperature high vibration frequency and low vibration pressure is propitious to the formation ofβcrystal.5. WAXD shows via low vibration pressure condition,βcontent in shear layer(23.7%) exceeds the static sample's(9.8%). But in the high vibration pressure sample's shear layerβcontent reduces. It can be seem that shear force can induce the formation ofβcrystal but there exists a optimal shear value, if exceeds this value, shear force will destroy the unstableβform crystal.6. Pole figures show that IPP of a static sample just orientates slightly along MD, while that of vibration sample orientate much stronger. The orientation of the normal ofα(040) plane of the sample obtained at a high vibrate pressure and low vibrate frequency is preferred in MD, and the orientation of the normal ofα(040) plane of the sample obtained at a relative low vibrate pressure and high vibrate frequency is preferred in ND. The unique plan ofβandγcrystal form does not show obvious orientation.