Authors:Maria Villanueva, I. Fraga, J. Rodríguez-Añón, J. Proupín-Castiñeiras, and J. Martín
The diffusive, calorimetric and thermal degradation behavior of different
epoxy-amine systems was investigated during water sorption at different temperatures
(23, 40 and 70°C). Experimental results showed that the water absorption
at these temperatures fitted well to Fick’s law. Influence of water
immersion during different periods of time on the glass transition temperatures
was studied by differential scanning calorimetry. Thermal degradation of saturated
samples was studied by thermogravimetric analysis. Dependence on the selected
curing cycle was also checked.
Authors:L. Barral, J. Cano, A. J. López, J. López, P. Nogueira, and C. Ramírez
The diffusive and dynamic mechanical behavior of the DGEBA/1,3-BAC epoxy resin system was studied during water absorption. The diffusion of water was investigated at 100% relative humidity, by immersion of specimens in water at 60, 80 and 100°C. In all absorption experiments, water diffusion followed Fick's law. Diffusion coefficients and saturated water concentrations are given for these temperatures. The activation energy for diffusion was determined from the relationship between the diffusion coefficient and the reciprocal of the absolute temperature. The value obtained was 31.2 kJ mol−1. Dynamic mechanical analysis of samples immersed in 100°C water and with various water contents showed both a shift of Tg, defined by thetanδ peak, to lower temperatures and a slight decrease in the dynamic modulus in the presence of water. These effects are probably a result of plasticization.
Authors:M. Rakszegi, G. Balázs, F. Békés, A. Harasztos, A. Kovács, L. Láng, Z. Bedő, and S. Tömösközi
Damaged starch, protein and arabinoxylan (AX) content and composition have been related to water absorption (WA) in a large set of samples. We tested 20 modern bread wheat cultivars bred in Hungary, 20 old Hungarian landraces, and 17 cultivars with special biochemical/functional characteristics from all around the world, this last set for international comparison. Grain was field grown in the 2011 and 2012 harvest seasons. Alinear mathematical model has been developed to estimate WA from protein content, starch damage, AX content and the relative amount of soluble proteins with strong correlation (r2 = 0.65) between measured and estimated data. The introduction of a new parameter, related to the cultivar dependent quantitative composition of soluble proteins and determined by lab-on-a-chip (LOC) analysis, largely improved the predictability of WA. Based on the large variation among the level of AX and certain soluble protein components in wheat flour and their significant contribution toWA determination, it was concluded, that these properties could be appropriate target traits to alter them during wheat breeding programs to improve the WA of wheat flour.
. , Hamard , E. , Cothenet A.
Measuring the waterabsorption of recycled aggregates, what is the best practice for concrete production?
Construction and Building Materials , Vol. 123 , 2016 , pp. 690 – 703