Effects of Molecular Length and Polarity of Chain Extenders on Microphase Separation and on Thermal and Mechanical Properties of Rigid Polyurethane Foam

In this work, rigid polyurethane materials were synthesized via a one-step polymerization method using isocyanate (MDI) and polyether polyol (4110S) as the main raw materials, with 1, 4-butanediol (BDO), 1, 6-hexanediol (HDO), diethylene glycol (DEG), and dipropylene glycol (DPG) as chain extenders. The influence of chain extender structure on the mechanical properties of rigid polyurethane was systematically investigated. The results indicate that when BDO was employed as a chain extender, the polyurethane exhibited the most uniform pore size distribution and the best mechanical properties. It was found that hydrogen bonding plays a dual role: on the one hand, it promotes microphase separation between soft and hard segments; on the other hand, it extends the molecular chains' length, which hinders segment separation and consequently constrains its mechanical properties. Further analysis reveals that the influence of molecular chain length on mechanical properties outweighs that of polarity.