Synthesis of polymer materials by low energy electron beam. III. Effects of polymerization temperature in EB solid‐state polymerization of semicrystalline urethane‐acrylate film

摘要

AbstractIn an electron beam (EB) polymerization of a urethane‐acrylate prepolymer, the polymerization temperature greatly affected the structure and properties of the resulting gel film. Urethaneacrylate, which was synthesized by the reaction of poly(butylene adipate)diol, 4,4′‐diphenylmethane diisocyanate, and 2‐hydroxyethyl acrylate, was used as a prepolymer. The prepolymer was semicrystalline and showed a melting point in the region of 50–60°C. The maximum polymerization rate of the prepolymer was obtained when the prepolymer film was irradiated in the temperature range of 25–40°C. EB polymerization below the melting point (Tm) of the prepolymer produced semicrystalline polyurethane‐acrylate gel films with a spherulitic texture. On the other hand, EB polymerization above theTmdestroyed the crystalline phase of the prepolymer to give transparent gel films. The gel film cured below theTmhad higher stress at yield, Young's modulus, and tensile strength than those cured above theTm. Such temperature effects are attributed to whether or not the EB polymerization proceeds with retention of crystalline structure of