中文摘要：

通过自主设计的多流体多次注射成型装置研究二次剪切应力场和复杂温度场对高密度聚乙烯晶体形态发展的影响．用偏光显微镜（PLM）和扫描电子显微镜（SEM）分析了多流体多次注射成型（multi—fluidmulti—injection molding，MFMIM）和传统注射成型（conventional injection molding，CIM）高密度聚乙烯（HDPE）制品的结晶形态，发现CIM试样小论是皮层还是芯层主要形成的是普通球晶，而在MFMIM中，由于皮层熔体受到二次强剪切应力作用，形成了环带球品和柱品的特殊结构，在形态分析的基础上，初步探讨了聚合物多流体多次注射成型制品结晶形态的形成机理．

英文摘要：

In order to explore the coupling effects of second shear flow and temperature fields on the formationas well as the evolution of crystal morphologies of high-density polyethylene （HDPE） , the crystal morphologies of the parts obtained by multi-fluid multi-injection molding （MFMIM） were investigated. The main feature of MFMIM is that the polymer melts in two different injection units are injected sequentially into the cavity to form an encapsulated sandwich-structure product. Polarizing light microscopy （PLM） results showed that some peculiar microstructures （e. g. cylindritic structures and ring-banded spherulites） were generated in the skin layer of the MFMIM parts. With the aid of scanning electronic microscopy （SEM） , a detailed description of cylindritic structure was obtained, which showed that the cylindritic structure consisted of some ring-banded spherulites. For comparison, the crystalline morphology of the sample molded by conventional injection molding （CIM） was also investigated. Different from the MFMIM parts, there were not observed any ring-banded spherulites or cylindritic structures in CIM parts except the common spherulites. And there was not a significant skin-core structure formed due to the higher temperature of the mold. Based on the comparison between the experimental results of the MFMIM parts and those of the CIM counterparts, it was concluded that the main reasons for ring-banded spherulites and cylindritic structures arising in the skin layer of MFMIM parts were the shearing and the complex thermo-mechanical fields provided by the secondary melt penetration process. Therefore, on the basis of the previous results, the mechanisms of ring-banded spherulites and cylindritic structures formation were discussed.