Effects of flexible and rigid parts of epsilon-caprolactone and tricyclodecanediol derived polyurethane on the polymer properties of epoxy resin

We report the synthesis of a novel polyurethane (PU) obtained from caprolactone (CL) and tricyclodecane diol (TCD-diol) and its reinforcing effect in the epoxy resin. Polycaprolactone (PCL)-TCD-polyol was synthesized by reacting TCD-diol with CL using tin(II)-2-ethylhexanoate. By changing the ratio of CL, PCL-TCD-polyol was synthesized with different molecular weights and chain lengths. Using PCL-TCD-polyol and polytetrahydrofuran (polyTHF) in a ratio of 1:1 with hexamethylene diisocyanate, polyurethane (PCL-TCD-PU) was prepared and used as a reinforcing agent with epoxy resin to improve the polymer properties. The mechanical and thermal properties of the epoxy cured specimens with and without the PCL-TCD-PU reinforcing agent were comparatively analyzed. The addition of PCL-TCD-PU with epoxy resin improved the tensile, impact, and flexural strengths, and it also had excellent physical properties that changed depending on the molecular weight and PU content of the TCD-polyol used in the PU. Furthermore, the fracture surface of the epoxy resin after the impact test had a specific pattern that was thoroughly analyzed by FE-SEM. Furthermore, thermomechanical analysis (TMA) showed that while increasing the PU content in the epoxy resin, the thermal expansion system is close to one, which clearly indicates that PCL-TCD-PU is expected to show excellent adhesive strength.