Investigation of the effect of foaming process parameters on expanded thermoplastic polyurethane bead foams properties using response surface methodology

Abstract

ABSTRACTExpanded thermoplastic polyurethane (ETPU) bead foams were fabricated by batch foaming with supercritical CO2 as blowing agent. On the basis of single factor investigation, the response surface methodology based on Box‐Behnken Design was used to investigate the influences of saturation pressure, temperature, and soaking time and their interactions on foaming behavior of ETPU. The results showed that saturation temperature was the most significant parameter affecting the expansion ratio, shrinkage ratio, and cell morphology of ETPU. Moreover, there was an interaction effect between saturation temperature and soaking time, wherein the expansion ratio of ETPU was more sensitive to change of soaking time at higher temperature. As the soaking time increased, the shrinkage of ETPU increased firstly and then leveled off, and the cell diameter decreased significantly. By applying the response surface methodology optimization, ETPU bead foams with final expansion ratio of 8.04, mean cell diameter of 74.2 μm, and average cell density of 1.46 × 107cell/cm3 can be obtained while the optimum conditions at saturation pressure of 15 MPa, saturation temperature of 100 °C and soaking time for 60 min. In addition, the dual melting peak of ETPU characteristics demonstrated that it is suitable for steam‐chest molding technology. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46327.