Viscoelastic Properties of Short Organic Fiber Reinforced Polyethylenes

Abstract

The effect of unmodified (nat) and azide modified (mod) short organic polyethylene terephtalate (PET) and Nylon 66 (PA) fibers on the properties of high and low density polyethylenes (HDPE and LDPE) has been investigated by dynamic mechanical analysis (DMA). The results have shown that the incorporation of both fibers gives rise to a sensible increase of the LDPE stiffness (storage modulus), this effect being more evident when the fibers were chemically treated with an azide derivative. However, in the case of the HDPE matrix an unusual behavior has been observed. In addition, a slight decrease of the damping factor (tan δ) of both matrices with the incorporation of the fibers takes place. The LDPE activation energy for the relaxation process decreases with the incorporation of both fibers whereas in the case of HDPE matrix this effect is only observed with the PET fibers. In all cases, the chemical treatment of the fiber surfaces with a diazide gives rise to an increase in the activation energy of the composites in relation to those prepared with unmodified fibers. The morphology of the composites has also been analyzed by scanning electron microscopy (SEM) and the results were in agreement with those previously obtained by DMA.