Research On The Key Technology Of Permeability Test Device Based On Differential Pressure

Plastic film and sheet are packaging materials for food, medicine and other daily use packaging, it is widely used in industrial and agricultural. The permeability of film and sheet direct impact packaging quality, it is necessary to permeability for its production and application.Now, Differential pressure method is one of the most widely used methods for testing film and sheet permeability. There are many factors to affect the test result which based on the differential pressure. Such as the leakage of test system, the environment temperature, the capability that included detector accuracy, effective range and stability of the temperature and pressure test device and the degasification of the film. It can greatly reduce impact of test results through appropriate extend the test pieces degassing time. Although it can improve the accuracy of permeability testing by increasing the accuracy and stability of the detector, it will inevitably lead to rapidly increase cost of test. Therefore, the key technology is control the permeability test device leakage and the environment temperature stable.Now, at domestic and foreign, the permeability test device based on Differential pressure method is single seal structure.For hign barrier film permeability test, it is difficult to test by single seal structure test device. Therefore, we should pay attention to research multi-layer seal structure of permeability test device. Access to domestic and foreign, there is not research multi-layer seal structure for permeability test device.The environment temperature is another important factor that affects the permeability test results.It can to achieve some effect in a certain range by using he fuzzy PID control on the PWM to control the test device.To improve the accuracy of temperature control, it is difficult to achieve by use the fuzzy PID control on the PWM. Therefore, it need to further research higher precision temperature control method and strategy.Based on this, this paper focuses on research multilayer seal structure of permeability test device, the design method of double and three seal structure are give. This paper focuses on research heat transfer model and temperature control of permeability test system which based on TEC, the heat transfer mathematical model of permeability test device is build. A higer accuracy temperature control method and strategy is given. The design principle of film and sheet permeability test device is give.Main research results and the innovations are as followed:(1) Research on double and three seal structure of permeability test device. Propose the design method of double and three seal structure for film and sheet permeability test device, established mathematical model for double and three seal structure of film and sheet permeability test device. Analyze the pressure changing characteristic of the double and three seal structure which caused by leakage. Give the corresponding simulation and experimental results, the result show that the double and three seal structure of permeability test device accord with the application requirement. The gap is filled in the field of permeability test at domestic and foreign by permeability test device seal structure.(2) Optimization of the double seal structure of permeability test device.Give the system critical time solution expression of double seal structure of permeability test device. Analyze the time flow resistance capacitance constant characteristic of the test device. At the condition of the total seal volume was limited, obtain the optimize structure rate of the double seal structure. Give double seal structure optimization method in theory. Give the corresponding simulation and experimental results, the result show that the optimization of the double seal structure is correct and reasonable.(3) Research on heat transfer model of permeability test device based on TEC.The first time propose and build the heat transfer mathematical model of the permeability test device which based on TEC. Give the analytic solutions of the temperature field in theory. Give the corresponding simulation and experimental results, the result show that the correctness of the transfer mathematical model and the analytic solutions of the temperature field. Provide the theory evidence for the deeper research the temperature control of film and sheet permeability test device.(4) Research on higer accuracy temperature control of permeability test based on the TEC.Propose a predict function control method based on the PWM for temperature control. Use the method to control the temperature of the permeability test device's cavity. Give the corresponding simulation and experimental results, the result show that the temperature control could effectively advance the dynamic properties and steady state precision of temperature control system, the method has pratical value.(5) Experiment and error analysis of film and sheet permeability test.Use the technology of double seal structure design and PFC temperature control based on the PWM. the permeability test experiment is done for film and sheet, the results show that test results are more accurate and stable. The error analysis and corresponding design discipline of film and sheet permeability test device are given.