Polyol and polyurethane containing bisphenol‐Z: Synthesis and application for toughening epoxy

Despite their excellent properties, epoxy resins have the disadvantage of low toughness. With the aim to improve the toughness of epoxy resin, polyol and polyurethane are synthesized using bisphenol‐Z (BPZ). The synthesized material is dispersed in the epoxy resin and used as a toughening agent. Polyol (modified bisphenol‐Z [MBPZ]‐OH) is synthesized by a ring‐opening polymerization of propylene oxide and caprolactone, and polyurethane (MBPZ‐PU) is synthesized by a one‐shot method using MBPZ‐OH and hexamethylene diisocyanate (HMDI). The effect of MBPZ‐PU on the mechanical strength of the epoxy resin is analyzed by monitoring the flexural and impact characteristics. The addition of the synthesized MBPZ‐PU improves the tensile strength, flexural strength, flexibility, and impact strength of the cured epoxy composite. Field‐emission scanning electron microscopy measurements indicate that the fracture surface had a specific pattern. Thermal properties such as the curing temperature, glass transition temperature (Tg), and modulus are investigated through differential scanning calorimetry, dynamic mechanical analysis, and thermomechanical analysis. Based on the results, MBPZ‐PU is expected to be applied to a wider field for increasing the toughness of epoxy.