The polyamide 66 （PA66）/lanthanum acetate blends with small amounts of salt loadings （≤ 1 wt% of PA） have been prepared in a twin-screw extruder. The rheology of PA66 and its blends has been investigated by a rot...The polyamide 66 （PA66）/lanthanum acetate blends with small amounts of salt loadings （≤ 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 η^＊ 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 （tanδ〈 1）, i.e., the melt changed from a viscoelastic liquid for unfilled polymer to a viscoelastic solid （G′ 〉 G″）. While the viscosity followed a strong shear thinning with increasing frequency, the η^＊ 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 pseudo- crosslinked network structure, which makes the glass transition temperatures （Tg） 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.展开更多
基金financially supported by the National Science-Technology Support Plan Projects(No.2014BAC03B05)the National Natural Science Foundation of China(No.51373184)Mo ST973 Research Program(Nos.2012CB933801 and 2014CB931803)
文摘The polyamide 66 （PA66）/lanthanum acetate blends with small amounts of salt loadings （≤ 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 η^＊ 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 （tanδ〈 1）, i.e., the melt changed from a viscoelastic liquid for unfilled polymer to a viscoelastic solid （G′ 〉 G″）. While the viscosity followed a strong shear thinning with increasing frequency, the η^＊ 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 pseudo- crosslinked network structure, which makes the glass transition temperatures （Tg） 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.
