Research On Extrution Foaming Of Thermoplastic Polyester Elastomer (TPEE)

In the paper, the foamed thermoplastic polyester elastomer(TPEE) boards have been prepared by melt extrusion with a single screw extruder, which are a new type of track materials with high damping properties. At present, the foamed TPEE boards have been mainly used as damping pads under the steel rail in the ballastless track of high-speed railway.Firstly, the composite foaming agent of TPEE have been prepared with a twin-screw extruder used as a reactor. when the mass ratio of azodicarbonamide(AC)/sodium bicarbonate(NaHCO3)/citric acid is 15/5/5, and the foam-coated agent was acrylates, the apparent density can reach to 0.6 g/cm3, tensile strength was 5.6 Mpa, at the same time, about 75% in the certain area is made up by cell between 40 and 120μm.Secondly, TPEE with shore hardness D40 or D45 has been crosslinked by isocyanate and epoxy crosslinking agent respectively. The gel content increased with the raise of crosslinking agent, when the content of isocyanate crosslinking agent is lphr, the compression set for foamed TPEE with Shore hardness D45 is less than 10%, and the cell less than 100μm account for 90% of all the number of cell in the certain area approximately. In the constant frequency, damping factor tanO is greater than 0.25, and damping temperature range is 130℃, so the crosslinked TPEE is poor sensitive to temperature.Moreover, TPEE with shore hardness D40 or D45 has been grafted by a graft polymer. with the analysis of the thermal decomposition temperature and the melt absorption peak, and the results show that the structure of TPEE is changed by the graft polymer, in addition, the thermal decomposition temperature and the melting absorption peaks is tend to high temperature. Meanwhile, the melt folw rate of TPEE with Shore hardness D45 can drop to 5g/10min. when the content of the graft agent is 6phr, the compression set is lowest, tensile strength is highest, the damping factor tanθand the range of damping temperature of TPEE with shore hardness D40 is 0.24 and 120℃respectively, in contrast, the corresponding value of TPEE with shore hardness D45 is 0.21 and 160℃, the range of damping temperature increases 40℃. For foamed TPEE with shore hardness D45, the rate of the closed cell is highest, and the cell structure is neat.Finally, the faomed TPEE have been prepared by the different extrusion die with flow-resisted set. And the results show that surface topography and section structure of the foamed TPEE are worse with the raise of die thickness. When the die thickness is 10mm, the surface topography is the most leveling, and also the uniform cell can be obtained.