The influence of rare earth ions on the rheological behavior of polyamide

Abstract

The polyamide 66 (PA66)/lanthanum acetate blends with small amounts of salt loadings (a parts per thousand currency sign 1 wt% of PA) have been prepared in a twin-screw extruder. The rheology of PA66 and its blends has been investigated by a rotational rheometer. The results suggested that with the salt loading in excess of 0.2 wt% the typical Newtonian viscosity plateau disappeared and both the low-frequency complex viscosities eta* and storage modulus G' of blends were much higher than those of neat PA66, the storage modulus was higher than the loss modulus at low frequencies (tan delta GaEuro(3)). While the viscosity followed a strong shear thinning with increasing frequency, the eta* and G' decreased significantly even lower than those of neat PA66 at high frequencies. The combination of dynamic mechanical analysis (DMA) and X-ray photoelectron spectroscopy (XPS) analysis has revealed that coordination effect occurred between lanthanum and carbonyl oxygen atoms in amide groups of the polymer to form pseudocrosslinked network structure, which makes the glass transition temperatures (T (g)) and storage modulus (E') of blends enhanced. The network structure formation-destruction and chains entanglement-disentanglement processes at different frequencies are responsible for the above rheological behaviors of blends.