Curing Of DGEBA Research Articles

Studies on the curing kinetics and thermal stability of diglycidyl ether of bisphenol‐A using mixture of novel, environment friendly sulphur containing amino acids and 4,4′‐diaminodiphenylsulfone

AbstractThis article describes the curing behavior of diglycidyl ether of bisphenol‐A using Cysteine (A)/ Methionine (B)/Cystine (C)/ mixture of 4,4′‐diaminodiphenyl sulfone (DDS) and Cysteine/DDS and Methionine/DDS and Cystine in various molar ratios as curing agent. Differential scanning calorimetry was used to study the cure kinetics by recording the DSC scans at heating rates of 5, 10, 15, and 20°C/min. The peak exotherm temperature was found to be dependent on the heating rate, structure of the amino acids and on the DDS/amino acids molar ratio. A broad exotherm was observed in the temperature range of 150–245°C (EA), 155–240°C (EB), and 190–250°C (EC). Curing of DGEBA with mixture of amino acids and 4, 4′‐diaminodiphenyl sulfone (DDS) resulted in a decrease in characteristic curing temperatures. Activation energy of curing reaction is determined in accordance to Ozawa's method and was found to be dependent on the structure of the amino acids and on the ratio of 4,4′‐diaminodiphenyl sulfone (DDS) to amino acid. Thermal stability of the isothermally cured resins was evaluated using dynamic thermogravimetry in nitrogen atmosphere. No significant change has been observed in the char yield of all the samples, but it was highest in the system cured using either Cystine alone (EC‐1) or a mixture of DDS/Cystine (EC‐2, EC‐3, and EC‐4). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Phosphorus‐containing epoxy resins: Thermal characterization

AbstractThree novel aromatic phosphorylated diamines, i.e., bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl} pyromellitamic acid (AP), 4,4′‐oxo bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl}phthalamic acid (AB) and 4,4′‐hexafluoroisopropylidene‐bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl}phthalamic acid (AF) were synthesized and characterized. These amines were prepared by solution condensation reaction of bis(3‐aminophenyl)methyl phosphine oxide (BAP) with 1,2,4,5‐benzenetetracarboxylic acid anhydride (P)/3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride (B)/4,4′‐(hexafluoroisopropylidene)diphthalic acid anhydride (F), respectively. The structural characterization of amines was done by elemental analysis, DSC, TGA, 1H‐NMR, 13C‐NMR and FTIR. Amine equivalent weight was determined by the acetylation method. Curing of DGEBA in the presence of phosphorylated amines was studied by DSC and curing exotherm was in the temperature range of 195–267°C, whereas with conventional amine 4,4′‐diamino diphenyl sulphone (D) a broad exotherm in temperature range of 180–310°C was observed. Curing of DGEBA with a mixture of phosphorylated amines and D, resulted in a decrease in characteristic curing temperatures. The effect of phosphorus content on the char residue and thermal stability of epoxy resin cured isothermally in the presence of these amines was evaluated in nitrogen atmosphere. Char residue increased significantly with an increase in the phosphorus content of epoxy network. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2235–2242, 2002