Experimental Studies On Mechanical And Rheological Properties Of PA/PTFE Blends

PA6/PTFE and PA66/PTFE blends with different PTFE contents are prepared by melt blending in twin-screw extrusion process, in which PA6 and PA66 are the continuous phase and PTFE is the dispersed phase. These two blends are exposed to 60Co-γirradiation; different irradiation doses (20kGy, 50kGy and 100kGy) are applied. The Melt rheology, impact fracture properties and the influences ofγirradiation on mechanical properties, water-absorptivity, melting and crystallization behavior are studied. Some preliminary conclusions can be drawn as follows:1. The water-absorptivity of the blends decreases with increase in PTFE content, while the flexural modulus initially increases to a maximum value and then decreases with further increasing the PTFE content. The Charpy impact strength and elongation to break of the blends are much smaller than those of the net PA.2. With irradiation dose increasing, the tensile strength, tensile modulus, flexural strength and flexural modulus increase, while the elongation to break, the Charpy impact strength and the water absorption ratio decrease. Moreover, absorbed water has different effect on the mechanical properties of the twoγ-irradiated blends. For the tensile strength, tensile modulus, flexural strength and flexural modulus of the wetγ-irradiated PA6/PTFE blends are greater than those of the dry blends; however these four mechanical variables of theγ-irradiated PA66/PTFE blends have negligible difference before and after water absorption.3. The complex viscosity of the blend melts decreases with the increasing shear rate, which exhibits pseudoplastic behavior. 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. 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.4. The melting temperature of PA6/PTFE blends increases with PTFE content, while the melting enthalpy decreases with PTFE content. For PA66/PTFE blends, the melting temperature increases negligibly with PTFE content (0%~15%), while the melting enthalpy also decreases with PTFE content. It is also shown that the melting temperature of the blends decreases a little with irradiation dose, while the melting enthalpy and the crystallization enthalpy increases with increase in irradiation dose.