Research On TPU Molding Injection Foaming Under Fixed Cavity And Core-back Process

Thermoplastic polyurethane elastomer(TPU)is an elastomer that can be plasticized by heating and dissolved by adding a solvent.It is also called thermoplastic polyurethane rubber.Because of its excellent physical properties and comprehensive performance,it is widely used in the fields of building materials,toys,auto parts,industrial parts and clothing accessories.In the process of application,the disadvantages of TPU's high hardness and high weight appeared.In order to improve the comprehensive performance of TPU products,domestic and foreign scholars have used a variety of methods for processing and molding.Although intermittent foaming molding can be used to obtain lightweight TPU foamed materials,the production efficiency is low.In this paper,through chemical foaming injection molding,the core-back process was added into traditional injection foaming molding,and the effects of the foaming system,injection process parameters and core-back process parameters on TPU injection foaming molding were systematically studied.The main research contents and conclusions are as follows:(1)In the traditional injection foaming molding process,the suitable nucleating agent and foaming agent were selected to constitute the foaming system,and the effects of nucleating agent contents and foaming agent contents on the cell structure,physical and mechanical properties of TPU injection foamed samples were studied.The results show that:the better foaming system is:nano-clay nucleating agent content 0.6wt%,AC foaming agent content 3wt%.(2)In the traditional injection foam molding process,the effects of different injection process parameters on the cell structure,physical and mechanical properties of TPU injection foam samples were studied.The results show that:the better injection process parameters are:injection temperature 190?;injection pressure 95.6MPa;injection speed 96.7mm/s.(3)In the traditional injection foaming molding,a core-back method is added.The effect of the core-back method on the TPU injection foaming molding process was studied and compared with the traditional injection foaming process.The results show that:the best core-back process parameters are:core-back pressure 53.1MPa;core-back speed 30%;mold temperature is normal temperature.Compared with the sample obtained by the traditional injection foaming process,the cell density increased by 22.7%;the average cell diameter decreased by 8.0%;the apparent density decreased by 2.2%;The rebound degree increased by 5.8%.