Jia-Zhuang Xu, Gan-Ji Zhong, Zhong-Ming Li
College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, China 

EXTENDED ABSTRACT: Injection molding is the most commonly used processing method in the polymer industry for its unique combination of high automation, high efficiency, and the ability to mold products with complex shapes and high dimensional accuracy. There are about 32% of polymer materials are processed into products through injection molding in the world, the polymer used for injection molding over 20 million tons every year in China. However, due to the short molding cycle and the existence of strong machining fields such as high pressure, high shear and high temperature change, the traditional research method can only adopt the "black box" model. To overcome this bottleneck, we developed the world's first high­throughput in-situ characterization device based on an industrial injection molding machine. Through the design and construction of special optical path, precision two-dimensional displacement platform, and external field control system, it successfully realized the combination of multiple X-ray characterization methods (WAXD/SAXS/USAXS) at the USAXS line station of Shanghai Light Source Phase II, and the processing parameters of the device fully covered the level of industrial injection molding processing, and could achieve millimeter-level time resolution and simultaneous characterization of multi-scale structures. It provides a strong hardware guarantee for the research of material genetic engineering in polymer injection molding. By using this device, we first revealed the polymer crystallization behavior under temperature gradient and pressure in injection molding, clarified the critical conditions for the formation of the specific crystalline structure, and realized the visualization of polymer injection molding. It is found that polyolefin has obvious orientation crystallization behavior and molecular weight dependence during injection molding. The B crystal formation induced by shear flow of polypropylene in injection molding and its dependence on melt temperature were found. The relationship between the machining parameters and the injection molding time was quickly determined through online experiments, which provided a new tool for the accurate control of the injection molding product structure and the realization of its high performance.
Keywords: Polymer; Injection molding; Properties; On-line research equipment