Effect of type of substitution in 4,4′‐bis‐(diaminodiphenyl) methane hardener on cure kinetics, mechanical, and flame retardant properties of tetrafunctional epoxy resins

Abstract

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.

Morphology, thermal and mechanical performance of epoxy/polysulfone composites improved by curing with two different aromatic diamines

“…As shown in Figure a, the molecular structures of DDM and DDS were similar, and the only difference was that a methylene structure (–CH 2 –) in DDM was replaced by a sulfone group (–SO 2 –) in the molecule of DDS. As reported in literature, the electron‐withdrawing inductive effect had a negative influence on the epoxy‐amine reaction, but on the contrary, the electron‐donating effect could improve the basicity and hence increase the reactivity of amine. Here, the sulfone group corresponded to electron‐withdrawing group whereas the methylene belonged to electron‐donating group.…”

“…The degree of miscibility and ultimate performance of epoxy composites can be tuned effectively with one kind or a combination of curing agents. Among them, the aromatic curing agents such as 4,4'‐diaminodiphenyl sulphone (DDS) and diaminodiphenyl methane (DDM) are largely used in the high performance composites, because the aromatic rings in DDS and DDM introduced into the crosslink networks during curing can provide better thermal and mechanical properties for the epoxy materials . As reported in literatures, the curing reaction, morphology and mechanical performance of the pure or thermoplastic modified epoxy systems cured with a single curing agent of DDM or DDS have already been studied, but the combined use of them has not been mentioned so far.…”

Novolac epoxy resin from 4,4′‐dihydroxybenzophenone: Thermal, thermomechanical, interfacial, and cure kinetics with DGEBA/DICY blend

“…The kinetic parameters of the crosslinking reaction were estimated from DSC using the variable peak exotherm method of Kissinger as represented by the eq. where R is the universal gas constant, β is linear heating rate, is the peak temperature in DSC exotherm, A is the Arrhenius frequency factor, and is activation energy.…”

Effect of phosphorus‐containing flame retardants on flame retardancy and thermal stability of tetrafunctional epoxy resin

“…According to eqn (1), E and ln A were calculated to be 71.98 KJ/mol and 18.9, respectively. The value of E is higher than 55.54 KJ/mol for TGDDM/DDM, but lower than 85.36 KJ/mol for TGDDM/DDS in the literature . These activation energies suggest the following order for increasing nucleophilicity of the curing agents: DDS < MHHPA < DDM.…”