Research on synthesis of polyurethane based on a new chain extender obtained from waste polyethylene terephthalate

Bis(2‐hydroxyethyl) terephthalate (BHET), the alcoholysis monomer of waste polyethylene terephthalate, can form a cross‐linked network structure with the polyurethane main chain because of the unique structure of active hydroxyl groups. In this work, organic small molecular BHET was applied as a new chain extender in polyurethane synthesis. A green and facile method was proposed to fabricate waterborne polyurethane (WPU) by recycling waste polyester. It was found that WPU was successfully prepared by using BHET as chain extender. Compared with polyurethane prepared by small molecular chain extender 1,4‐butanediol (BDO), mechanical strength and thermal stability of polyurethane were remarkably enhanced by the incorporation of BHET. Meanwhile, the water absorption rate of the polyurethane is reduced. The tensile strength of WPU/BDO materials with 3.77 wt% BDO was 5.3 MPa, while WPU/BHET materials with 3.77 wt% BHET was 9.4 MPa. Furthermore, the elongation at break of WPU/BHET materials reached the maximum with 5.66 wt% BHET. Moreover, WPU/BHET materials prepared by using BHET as a chain extender have better thermal stability in high temperature environments. BHET with distinctive structure and the uniform dispersion will have more potentials for the preparation of high‐performance polyurethane composites, especially for green recycling of polyester materials. WPU/BHET materials with improved mechanical properties and thermal stability.