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ABSTRACT:The nature of the substituent in 4,4Ј-bis-(diaminodiphenyl) methane (DDM) hardener on the cure kinetics, mechanical, and flame retardant properties of N,N,NЈ,NЈ-tetraglycidyl diaminodiphenyl methane (TGDDM) resin is investigated in comparison with unsubstituted DDM and widely used 4,4Ј-bis-(diaminodiphenyl) sulfone hardeners. Dynamic differential scanning calorimetry (DSC) and cure rheology studies showed that the substitution decreased the reactivity of the amine. An electron-withdrawing chlorine substituent was found to be more effective than an electronreleasing methyl group in reducing the amine reactivity. Substituted and unsubstituted DDM hardeners showed two peaks in their DSC thermograms that were due to steric hindrance in the former and deficiency of amine in the latter. Substitution showed its effect on the mechanical properties and glass-transition temperature. The flexural modulus was increased; however, the Izod impact and glass-transition temperature were decreased in substituted amine systems. The limiting oxygen index results showed higher flame retardancy in the chlorine substituted hardener system compared to other hardener systems that were studied.

Four type of Carbon/Carbon (C/C) composite brake discs (A, B, C, D) were manufactured using different process routes, using spun yarn graphitised carbon fabric as reinforcement. These discs were densified with different types of carbon matrices derived from different precursor materials. C/C brake disc of type A is having carbon matrix derived from pitch precursor, type B has a mixture of resin and pitch derived carbon matrices, type C has a combination of resin derived, pyro and pitch derived carbons and type D has pyro and pitch derived carbon matrices. Friction and wear performance of these brake discs were studied by simulating aircraft landing braking energies (normal and over load) corresponding to one interface using disc-on-disc dynamometer. It was found that the type of carbon matrix influences the nature of friction film formed, which in turn affects the wear rate of C/C brake discs. It was also discussed how the matrix characteristics affected the mechanical properties and the friction film formed affect the coefficient of friction of each type of disc.