| Due to the use of congener polymer,the mechanical properties of single polymer composites(SPC)are not only higher than those of ordinary polymer parts,but also can be recycled and have good interfacial adhesion.SPC prepared by injection molding can effectively avoid the defects caused by traditional hot pressing and other processes,and have high production efficiency,many kinds of available materials,simple manufacturing process and other advantages.However,due to the influence of many process parameters,the properties of the molded parts are not stable,and difficult to control.Based on the experimental results of existing semi-open SPC specimens,the closed SPC specimens were improved and designed for comparison.In order to save time and material resources before developing the forming die,the formability of the specimens was simulated.Due to a big gap between the simulation results and the experimental data.After comparing and correcting with the velocity curves of melt flow front measured by visual experiments,the initial velocity entering the channel and speed gradient of melt of above 230 ?plasticizing temperature is the same as the measured value.Then the modified parameters are used to simulate the enhanced phase flow length with different cross-section diameters.The results show that the flow length is exponential with the injection velocity.The increase of injection velocity and the decrease of cross section diameter size and melt temperature make the index decrease and the range of flow length decrease.Choosing the size of 2mm diameter enhanced phase according to the simulation results.The forming die of the closed SPC parts was designed,the samples under different molding parameters were prepared and the tensile test was carried out.The mechanical property of the closed SPC article can reach 377.6MPa,which was improved by 12% than those of ordinary polymer parts,lower than 24% of the semi-open type,which means the mechanical properties upgrade ability of the closed parts are weakened.Closed matrix is not conducive to the shear orientation of melt and retention of orientation.Because the closed matrix can not directly be observed the flow state of melt by visualization,according to the direct influence of viscosity on the flow characteristics of melt and the influence of temperature on the viscosity,the changes of temperature field of reinforced phase melt flow in closed SPC parts was measured by infrared temperature sensor.The data show that the melt temperature increases first and then decreases after entering the groove.Increasing injection speed,plasticizing temperature and mould temperature willincrease the melt temperature,increase the temperature rise range and decrease the cooling range by increasing shear heat or reducing heat dissipation at the later stage of flowing,which is beneficial to maintain better fluidity of the melt during the whole filling process.The visualization of temperature field in injection molding is put forward for the first time.By combining the measured data of infrared temperature sensor with the position of the cavity and time,the dynamic nephogram of melt temperature distribution in the cavity can be visually displayed,which is conducive to rapid prediction of the quality of the parts or finding out the causes of quality defects.In this paper,the controllability of the performance of the parts is realized through the design and simulation of the new SPC structure,experimental preparation of closed SPC parts and mechanical and temperature measurement experiments.It was found that the closed SPC parts were not conducive to melt heat dissipation due to the closure of the matrix,which kept the melt at a higher temperature,a lower viscosity and a better filling property.The orientation was weakened by the smaller velocity gradient and shear rate,and the orientation was increased by the longer cooling time.Finally,the mechanical properties of SPC parts are enhanced by a small margin. |
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