Enhanced foaming behaviors and compression properties of thermoplastic polyurethane via constructing micro-crosslinking structure assisted by chain extender

Thermoplastic polyurethane (TPU) foams are favorable for their elasticity and compression performance. However, high shrinkage rate, low expansion ratio, and insufficient compression performance greatly limit its application. In this work, to prepare the desired TPU foam and to gain insight into the influence of micro-crosslinking structure on their effect, crosslinked TPU foams were prepared and subsequently foamed by supercritical CO2 foaming technology. Effects of micro-crosslinking structure on the rheological and foaming behavior of samples were systematically investigated. Rheological results indicated that the introduction of a chain extender in the TPU matrix increases the branching degree of molecular chain. Compared with pure sample, the expansion ratio of composite foam increased from 3.5 to 6.5 and specific compressive strength from 3.19 to 11.81 MPa.