Dynamic mechanical and thermal analysis of vinylester-resin-matrix composites reinforced with untreated and alkali-treated jute fibres

Abstract

Vinylester-resin-matrix composites reinforced with untreated and 5% NaOH treated jute fibres for 4 and 8 h with different fibre loading were subjected to dynamic mechanical and thermal analysis to determine their dynamic properties as a function of temperature. For all the composites the storage modulus, E′, decreased with increase in temperature, with a significant fall in the temperature range 110°–170 °C. For the treated composites, the rate of fall, d E′/d T, had an inverse relationship with the defect concentrations in the composites. The lowest defect concentrations in the 4 h treated composites corresponded to the highest rate of fall. The glass transition temperature, T g, of the unreinforced resin, corresponding to the loss modulus peak, was 101.2 °C, whereas that of the composites increased by nearly 28 °C on account of the restricted mobility of the resin molecules in the presence of the fibres. In the case of the treated composites, the T g value showed a decreasing trend (128 to 125 °C). Unlike the plain resin, a tiny hump was observed in the loss modulus, E″, curves of all the composites around 166 °C, which became broader and more prominent with increase in the jute fibre content. The very high tan δ value of the resin decreased in the composites, indicating that the addition of the fibres lowered the damping capacity of the composites.