Experimental studies on water-absorptivity and rheological behavior of PTFE/PA6 and PTFE/PA66 blends

The effects of PTFE content on water-absorptivity, notched impact strength and complex viscosity of PTFE/PA6 and PTFE/PA66 blends were investigated by water immersion test, Charpy impact fracture test and dynamic rheology measurement in this paper. It is shown that the amount of absorbed water in the blends decreases with increasing PTFE content, indicating that the PTFE phase restrains the PA phase from water absorption. Although the addition of PTFE causes a decrease in notched impact strength of the blends, as compared to pure PA, the absorbed water has little effects on the notched impact strength of the blends. It is also shown that the complex viscosity of the blends varies with the PTFE content; an appropriate content of PTFE can improve the processability of the blends. Moreover the complex viscosity of the blend melts decreases with increasing frequency at given temperatures, which exhibits pseudoplastic behavior. As to the temperature dependence of complex viscosity of the blend melts, an interesting phenomenon was observed. The complex viscosity decreases with increasing temperature for PTFE/PA6 melts, while it increases with temperature in a manner of power law for PTFE/PA66 melts.