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

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 110degrees-170 degreesC. For the treated composites, the rate of fall, dE'/dT, 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 degreesC, whereas that of the composites increased by nearly 28 degreesC 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 degreesC). Unlike the plain resin, a tiny hump was observed in the loss modulus, E, curves of all the composites around 166 degreesC, which became broader and more prominent with increase in the jute fibre content. The very high tandelta value of the resin decreased in the composites, indicating that the addition of the fibres lowered the damping capacity of the composites. (C) 2002 Elsevier Science Ltd. All rights reserved.