A. Torres

Bio: A. Torres is an academic researcher from University of A Coruña. The author has contributed to research in topics: Epoxy & Diglycidyl ether. The author has an hindex of 9, co-authored 12 publications receiving 567 citations.

Effect of water sorption on the structure and mechanical properties of an epoxy resin system

Abstract: The characteristics of sorption and diffusion of water in an amine-cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature. Water-sorption experiments and dynamic mechanical analysis (DMA) were performed. Tensile stress–strain and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interactions between water molecules and polar groups of the network were used to explain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelastic behavior was related both to the water-sorption processes and to the microstructure of the system. An important impact of water uptake on the tensile properties at break was also appreciated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 71–80, 2001

Isothermal curing by dynamic mechanical analysis of three epoxy resin systems: Gelation and vitrification

Abstract: Times to gelation (tgel) and times to vitrification (tvit) during isothermal curing for the epoxy systems diglycidyl ether of bisphenol A (DGEBA)/1,3-bisaminomethylcyclohexane (1,3-BAC), tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM)/4-4′-diaminodiphenylsulfone (DDS), and TGDDM/epoxy novolac (EPN)/DDS were measured at different curing temperatures. This article reports on a method to determine tgel and tvit by dynamic mechanical analysis (DMA). Gelation was determined at the onset of the storage modulus or by the peak of the loss factor. Vitrification was defined as the curve of the storage modulus as the curve reached a constant level (endset) in DMA tests. The experimental values obtained for tgel and tvit were compared with values obtained by other experimental methods and with theoretical values (tgel's) or indirect determinations (tvit's). From kinetic analysis by differential scanning calorimetry, conversions corresponding to gelation were obtained for the three systems; this yielded a constant value for each system that was higher than theoretical value. Values of the apparent activation energies of the DGEBA/1,3-BAC, TGDDM/DDS, and TGDDM/EPN/DDS epoxy systems were obtained from plots of tgel's against reciprocal temperatures. They were 53.2, 58.2, and 46.5 kJ/mol, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 78–85, 2002

Applications of FTIR on Epoxy Resins - Identification, Monitoring the Curing Process, Phase Separation and Water Uptake

Abstract: Epoxy resins are a family of thermosetting materials widely used as adhesives, coatings and matrices in polymer composites because of the low viscosity of the formulations, good insulating properties of the final material even at high temperatures and good chemical and thermal resistance (May, 1988). Epoxy thermosets can be described as 3D polymer networks formed by the chemical reaction between monomers (“curing”). This 3D covalent network structure determines the properties of thermosetting polymers: unlike thermoplastics, this kind of polymers does not melt, and once the network has been formed the material cannot be reprocessed. Maybe one of the main advantages of epoxy thermosets is that the starting monomers have low viscosity so that complex geometries can be easily shaped and fixed after curing the monomers. Thus the formation of the network via chemical reaction is a key aspect in this kind of materials.