Viscoelastic properties of short organic fiber reinforced polyethylenes

The effect of unmodified (nat) and azide modified (mod) short organic polye thylene terephtalate (PET) and Nylon 66 (PA) fibers on the properties of hi gh and low density polyethylenes (HDPE and LDPE) has been investigated by d ynamic mechanical analysis (DMA). The results have shown that the incorpora tion of both fibers gives rise to a sensible increase of the LDPE stiffness (storage modulus), this effect being more evident when the fibers were che mically treated with an azide derivative. However, in the case of the HDPE matrix an unusual behavior has been observed. In addition, a slight decreas e of the damping factor (tan delta) of both matrices with the incorporation of the fibers takes place. The LDPE activation energy for the relaxation p rocess 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 cas es, 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 th ose prepared with unmodified fibers. The morphology of the composites has a lso been analyzed by scanning electron microscopy (SEM) and the results wer e in agreement with those previously obtained by DMA.