Research On The SCF Delivery System

Microcellular plastics occupy a large share in the plastic products and it is widely used in all walks of life. Microcellular plastics refer to the plastics whose cells average diameter is not exceeding 100μm and whose cell density range from109 to 1015 per cubic centimeter. Microcellular injection molding process base on supercritical fluid developments rapidly because it has no pollution and blowing agents are readily available and inexpensive. Its industrial production has been achieved in foreign.The key point of microcellular injection molding process is preparing the homogeneous distribution single-phase solution of supercritical fluid and polymer melt.The prerequisite of forming a high-quality single-phase solution is injecting supercritical fluid into the injection molding machine barrel uniformly, continuously and steadily during plasticizing process. So the key issue of microcellular injection molding is the delivery of supercritical fluid. The main work of the project is to design a supercritical fluid delivery system to meet the needs of microcellular injection molding process and study different ways for transporting supercritical fluid.At first injecting supercritical fluid into the barrel with the high-frequency pulse way was studied. Then the hardware part of this approach was designed and built to experiment. Formation mechanism and effect factors of the initial gas surging found in above experiment were also researched.Then the way of flow restricted delivery was in-depth studied and hardware pipeline, control system and data acquisition system were designed. Microporous flow restricted orifice was designed to make the injecting of supercritical fluid more uniformly, continuously and steadily.The relationship among gas volume of a plasticizing cycle, delivery pressure, back pressure, diameter of flow restricted hole and injection time was established by the mathematical model. The correctness of the mathematical model was tested by experiments and it laid a theoretical foundation for fully automated control of supercritical fluid deliveryAt last the hardware pipeline, control system and interactive interface of the fully automated control system for supercritical fluid delivery were designed after the study of the way of flow restricted and high-frequency pulse delivery.