Studies on the toughening of epoxy resin modified with varying hyperbranched polyester-toluene diisocyanate content

Epoxy resins have long been used in many fields like structural, coating, aerospace industries, etc., but their main drawback is brittleness which can be improved by using toughening agents. In the present study, a novel pathway for the toughening of diglycidyl ether of bisphenol-A based epoxy resin has been carried out using hydroxyl terminated hyperbranched polyester of third generation (HBP-G3) that have been covalently linked to the epoxy resin through toluene diisocyanate (TDI) which serves as a linkage between the hydroxyl groups on the epoxy resin and HBP resulting in the formation of HBP-Polyurethane/Epoxy (HBP-PU/Epoxy) blends. The synthesized HBP-G3 was characterized using spectral and physical methods. Though the thermal stability, glass transition temperature and flexural properties of the HBP-PU/Epoxy blends are declined, a significant gain in the impact behavior (up to 30 %) was observed with increasing content of HBP-TDI (upto 12.5 wt.%) in epoxy matrix, which is further confirmed by the existence of heterogeneous morphology from SEM micrographs.