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

Abstract

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 iso-thermal curing condition using the differential scanning calorimeter (DSC). Meanwhile, their thixotropic properties were measured using a rheometer at 25 °C. The relation between curing kinetics and thixotropic properties was discussed. It is found that when BAE/PA system is cured under 50–100 °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 °C. When cured below 80 °C, the curing process changed from chemical-controlled reaction into diffusion-controlled reaction at the critical curing degree (αc). αc decreases with the decrease of curing temperature. When filled by different kinds of fillers, curing kinetics at 90 °C and thixotropic properties of the systems at 25 °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.

Keywords

• Curing kinetics
• Thixotropic properties
• Epoxy resin
• Fillers