Effect of structure of Nitrogen, Sulfur and tin derivatives on the properties of epoxy resins

Abstract

Epoxy resins have been used successfully in a wide range of applications spanning from electronic products such as printed circuit boards to advanced aerospace structures. Many thermoset resins have been synthesized to meet the demands of defence, aerospace and electronic industries. Epoxy resins are most commonly used matrix resin in structural applications such as laminates and composites. This is primarily due to its fluidity, low shrinkage during cure and ease of processing. The cured resins have good mechanical properties (ultimate tensile strength, modulus elongation at break, toughness and fatigue resistance), low moisture absorption, relatively poor thermal stability and flame resistance. The present thesis deals with the curing and thermal behaviourof epoxy resin using tin derivatives, Biuret and aromatic imide-amines. Curing kinetics of diglycidyl ether of bisphenol A (DGEBA) in the presence of Phenylmethyltin dichloride (PMTC), Phenylethyltin dichloride (PETC), butylmethyltin dichloride (BMTC) and dimethyltin dichloride (DMTC) were investigated by the Differential Scanning Calorimetery. In the DSC scans of all the samples, a broad exothermic transition was observed. Single exotherm was obtained in all samples. The peak exotherm temperature was higher in case of DBMTCas compared to sample DPMTC, DPETC and DDMTC. The heat of polymerization was decreased as the heating rate was increased. The dynamic method was used in the present study and the DSC scans were recorded at different heating rates for the samples.The relative thermal stability of the cured resins was evaluated by comparing initial decomposition temperature (IDT), temperature of maximum rate of mass loss (Tmax), final decomposition temperature (FDT) and percent char yield at 8000C. All the samples were stable up to 235oC. Single step degradation was observed in all the samples. The char yield was lowest in case of resin cured with DMTC and highest in case of resin cured with PETC.