Effect of chain topological structure on the crystallization, rheological behavior and foamability of TPEE using supercritical CO2 as a blowing agent

Thermoplastic polyether ester elastomer (TPEE) has been reacted with different multi-functional group modifiers, such as 2,2'-bis(2-oxazoline) (2,2'-BOZ) and triglycidyl isocyanurate (TGIC), to create long chain TPEE and highly branched TPEE respectively by reactive processing. Both chain extension and branching processes could improve the complex viscosity and modulus, but TPEE with a branched structure showed distinguished strain-hardening behavior. The branched structure can also accelerate crystallization processes. In the foaming process, TPEE with branched chains have a higher expansion ratio, higher cell density and wider foaming window when compared with TPEE with long chains. The branched structure can prevent cells from collapsing to obtain foamed TPEE with high expansion ratios ranging from 1.5 folds to 16 folds, cell diameters ranging from 3 mu m to 13 mu m and a cell density between 3.6 x 10(8) cells/cm(3) and 7.1 x 10(9) cells/cm(3).