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通过自主设计的动态保压注塑成型装置研究剪切应力场下聚丙烯(PP)熔体在近熔点处冷却结晶的晶体结构.用扫描电子显微镜(SEM)、示差扫描量热法(DSC)和广角X射线衍射(WAXD)分析了PP试样在近熔点处冷却后从表层到剪切层的结晶结构的变化.SEM研究表明,与传统注塑成型样品(SL)和剪切力场中高熔体温度下冷却得到的试样(DH)相比,近熔点附近冷却得到的PP试样(DL)从表层到剪切层的结晶结构和形态有明显变化.DL从表层到剪切层均生成了尺寸较大的取向结晶结构,无明显的串晶产生.DSC研究表明,与SL和DH相比,DL剪切层无脊纤维晶熔融峰且晶片熔融温度较高,证明其样品内部晶片尺寸较大.WAXD进一步研究显示,DL内部主要晶面(110,040和130)的结晶尺寸与SL和DH相比并没有发生明显改变.
The crystal structure of polypropylene (PP) melt at the near melting point under shear stress was studied by a self-designed dynamic pressure-retaining injection molding device. The crystal structure of PP melt was analyzed by scanning electron microscopy (SEM), differential scanning calorimetry Wide-angle X-ray diffraction (WAXD) analysis of the PP sample after cooling near the melting point from the surface to the shear layer of the crystal structure changes.SEM studies have shown that, compared with the traditional injection molding (SL) and shear stress field high melt The crystallization structure and morphology of the PP sample (DL) cooled near the melting point from the surface layer to the shear layer obviously changed compared with the sample (DH) Compared with SL and DH, DL shear layer has no spine fiber melting peak and the melting temperature of the wafer is higher, which proves that the internal wafer size of the sample is smaller than that of SL and DH Further studies by WAXD show that the crystallographic size of major crystallites (110, 040, and 130) within the DL does not change significantly compared to SL and DH.