Structure and properties of polycarbonate diol‐based thermoplastic polyurethanes with copolymerized HMDI / MDI hard segments

Abstract

Aiming at the unbalanced performance and limited application scenarios of neat 4,4′‐methylenediphenyl diisocyanate (MDI) and hydrogenated MDI (HMDI)‐based polycarbonate diol (PCDL) thermoplastic polyurethane (TPU), a series of TPUs with copolymerized HMDI/MDI hard segments were fabricated via a semi‐prepolymer two‐step chain‐extension method using PCDL as the soft segment and 1,4‐butanediol as the chain extender. The regulation mechanism of copolymerized hard segment ratio on the microphase separation and hard domain stacking structure of TPU was systematically investigated through multiple characterizations. The enhancement mechanism of mechanical and hydrolysis properties derived from hydrogen bond reinforcement of MDI, as well as the synergistic effect of HMDI on eliminating photosensitive structures and improving weather resistance and light transmittance, were clarified. The results indicate that adjusting the HMDI/MDI ratio can effectively balance the mechanical performance and weather resistance of TPU. Optimal formulations applicable to indoor, semi‐outdoor and outdoor decorative scenarios were successfully screened out. This work provides theoretical guidance and technical references for the structural design and performance optimization of scenario‐oriented decorative TPUs. © 2026 Society of Chemical Industry.