Epoxy benzoxazine based ternary systems of improved thermo-mechanical behavior for structural composite applications

Ternary mixtures of various ratios of bisphenol F benzoxazine as a hardener for bisphenol F novolac epoxy (ER) and diglycidal ether of polyethylene glycol (EL) resins were made in order to study the visco elastic and thermo mechanical properties in comparison with homo polymerized polybenzoxazine (F-a). FTIR, and DSC were used to characterize the cure characteristic. The dynamic mechanical analyzer and thermo gravimetric analysis were investigated on F-a and ternary samples. An improved Tg of curable ternary mixture with 48.1 and 3.1 wt% of ER and EL respectively with benzoxazine resin was achieved based on trends in the ternary diagram. The ternary samples were thermally stable up to 370 degrees C when compared to F-a. Investigation of fracture toughness and SEM images showed improved fracture toughness for the samples with 52% binary epoxy mixture in the ternary system. The newly developed ternary mixtures showed improved service temperature, thermal stability, cross linking density, processing window and fracture toughness with minimum brittleness when compared to polybenzoxazine. The applicability of the developed ternary mixture was demonstrated by preparing an S glass fabric reinforced composite with F-f. It was observed that this S glass fabric composite has improved flexural strength, flexural modulus, ILSS, Shore D hardness & hydrolytic stability when compared to the polybenzoxazine composite and was found to be very useful for high performance structural applications.