Effects of curing program on mechanical behavior and water absorption of DGEBA/TETa epoxy network

Abstract

Water uptake in organic coatings remains an interesting challenge for fundamental and applied researches because chemical, physical, and mechanical properties are concerned. The polymer network, which is affected by the curing program, is a key factor for water absorption. In this work, an epoxy network based on diglycidyl ether of bisphenol A and a hardener triethylentetramine was cured at different temperatures: below T g (protocol 1) and above T g (protocol 2). DMA, Differential Scanning Calorimetry (DSC), and FT-IR measurements showed that both protocols allow to obtain totally cured networks. However, DSC and DMA results revealed that both cured networks present different levels of homogeneity, depending on the different curing conditions, which affect the free volume and the activation volume associated with visco-elastic properties. The mechanical properties of free films and water sorption behaviors were investigated as function of cured conditions. It was found that protocol 1-cured networks present higher mechanical properties and was less affected by water ingress than protocol 2-cured systems, leading to better barrier properties. These results highlight the influence of the curing program onto the heterogeneous distribution of the epoxy network.

Ionic liquids as reactive additives for the preparation and modification of epoxy networks

“…Moreover, the phosphinate ionic liquid made a network with higher crosslink density which expressed by the highest T g (141 °C) among all systems. This value is also higher than the glass transition temperature measured by DSC of different system described in the literature such as the DGEBA/TETA system, where a glass transition of 130 °C was obtained . The effect of the amount of phosphate ionic liquid was also studied.…”

Controlled synthesis and evaluation of cyanate ester/epoxy copolymer system for high temperature molding compounds

“…To evaluate the degradation performance and mechanism under high humidity, moisture absorption tests for CE/EP copolymers were conducted in boiling water. As shown in Figure , water uptake decreased with a decreasing molar ratio of cyanate ester, with the exception that the moisture absorption level of CE/EP‐13 exceeded that of CE/EP‐12 after 125 h. Moisture absorption of resin depends on the free volume in the cured polymer and the polarity of the chemical structures . Micro‐cracks generated in harsh environment like boiling water may have also contributed to the increasing amount of water absorbed.…”

Enhanced dispersion of lignin in epoxy composites through hydration and mannich functionalization

“…The DMA data, shown in Figure , indicates that the Neat, IMM, HL, HH, ML, and MRL samples had similar storage moduli and a similar glass transition, as shown in Table . These values are also similar to those reported in literature . In the ML, MH, and MRL, the glass transition region broadened appreciably compared with the Neat, as shown in Table .…”