New Stratagem for Designing High-Performance Thermoplastic Polyurethane by Using a New Chain Extender

The high content and regular distribution of hard segment (HS) are necessary to achieve high-performance thermoplastic polyurethane (TPU), and the HS unit of TPU is generated from the reaction of diisocyanate and chain extender. However, the traditional chain extenders are mainly aliphatic diol that cannot provide rigid groups to improve polyurethane performances. Herein, a novel chain extender bis(hydroxyethyloxycarbonylamino)hexane (BHH) that contains two urethane groups is designed and used to construct high-performance TPU by increasing content and regular distribution of HS. BHH is synthesized using ethylene carbonate (EC) and hexamethylenediamine (HDA) via a ring-opening reaction. Subsequently, the effect of BHH on the polyurethane performances is studied with respect to a typical TPU by using polytetramethylene ether glycol (PTMG) and hexamethylene diisocyanate (HDI) as the starting materials. The amount of HDI considerably differs for each polyurethane, aiming to ensure the same total content of urethane groups. When compared with the traditional ethylene glycol-extended polyurethane, the size and distribution of the HS domains of the BHH-extended polyurethane are obviously more homogeneous, which proves BHH-extended polyurethane has better microphase separation. Furthermore, ordered hydrogen bonding, the mechanical properties, and heat-resistance performance are significantly improved, suggesting a potential method to design TPU delivering outstanding performance.