Synergistic Optimization of Mechanical and Tribological Properties of Polyurethane through Chain Extender Regulation

Abstract

Developing polyurethane (PU) elastomers that simultaneously combine high strength, toughness, and wear resistance remains challenging. Here, PU elastomers were prepared from polycarbonate diol and hexamethylene diisocyanate using mixtures of N,N′-bis(2-hydroxyethyl)oxamide (BHO), a hydroxyl-functional chain extender, and 2-(4-aminophenyl)-5-aminobenzoxazole (APBOA), an aromatic diamine. Samples are denoted PUX, where X represents the APBOA molar fraction among the chain extenders; thus, PU7 contains APBOA and BHO at a 70:30 molar ratio. PU7 exhibited a tensile strength of 70.2 ± 0.5 MPa, elongation at break of 2229.5 ± 173.2%, and toughness of 538.4 ± 48.5 MJ m–3. Its excellent mechanical performance originated from uniformly distributed granular hard-segment domains formed through the combined effects of rigid APBOA units and hydrogen-bonding interactions. Under water-lubricated conditions, PU7 achieved a wear rate of 4.69 × 10–5 mm3 N–1 m–1, corresponding to improvements of 88.8% and 82.8% over PU (0 mol % APBOA) and PU10 (100 mol % APBOA), respectively. Cyclic tensile hysteresis supported its enhanced energy-dissipation capacity, which, together with its optimized hard-domain morphology, suppressed friction-induced damage. This chain extender regulation strategy provides PU elastomers with balanced mechanical robustness and wear resistance.