Curing kinetics and thixotropic properties of epoxy resin composites with different kinds of fillers

Effect of inorganic fillers, cement powder, Na-bentonite, flay ash, on curing kinetics of bisphenol-A epoxy resin and polyamide (BAE/PA) system was investigated under isothermal curing condition using the differential scanning calorimeter (DSC). Meanwhile, their thixotropic properties were measured using a rheometer at 25 degrees C. The relation between curing kinetics and thixotropic properties was discussed. It is found that when BAE/PA system is cured under 50-100 degrees C, the overall reaction order (m + n) decreases with increasing temperature from 2.63 to 1.83. The whole curing reaction process can be described by the Kamal model at temperatures above 90 degrees C. When cured below 80 degrees C, the curing process changed from chemical-controlled reaction into diffusion-controlled reaction at the critical curing degree (alpha(c)). alpha(c) decreases with the decrease of curing temperature. When filled by different kinds of fillers, curing kinetics at 90 degrees C and thixotropic properties of the systems at 25 degrees C were studied. It is found that compared with fly ash and cement powder, the system with Na-bentonite has the largest thixotropic hysteresis hoop area and changes into diffusion control reaction at lower curing degree. Decreasing particle size and increasing mass fraction of Na-bentonite increased the thixotropic properties of the filled system and consequently improved the overall reaction order. It means that high surface activity and thickening effect of Na-bentonite make the epoxy-amine system shows a stronger autocatalytic effect. (C) 2022 The Author(s). Published by Elsevier B.V.