The effects of polytetrafluoroethylene (PTFE) content on water-absorptivity, tensile strength, flexural strength, and notched impact strength of polytetrafluoroethylene/polyamide 6 (PTFE/PA6) and polytetrafluoroethyle...The effects of polytetrafluoroethylene (PTFE) content on water-absorptivity, tensile strength, flexural strength, and notched impact strength of polytetrafluoroethylene/polyamide 6 (PTFE/PA6) and polytetrafluoroethylene/polyamide 66 (PTFE/PA66) blends were investigated by water immersion test, uniaxial tensile test, three-point test, and Charpy impact fracture test. The water-absorptivity in the blend decreases with increasing PTFE content, which indicates that the PTFE phase restrains the polyamide phase from water absorption. For water-free blends, the addition of PTFE causes a reduction in tensile strength, while for water-absorbed PTFE/PA6 blends, the tensile strength increases with increasing PTFE. Simultaneously, the absorbed water improves the elongation, but results in a notable reduction in flexural strength of the blends. Although the addition of PTFE causes a reduction in notched impact strength of the blends, as compared to pure polyamide, the absorbed water has little effects on the notched impact strength of the blends. Finally, the effects of temperature and loading frequency on complex viscosity parameters of PTFE/PA6 and PTFE/PA66 melts were tested. It is found that the complex viscosity of PTFE/PA6 melt is reversed with increasing temperature and shear velocity, but that of PTFE/PA66 melt increases approximately in exponential form with increasing temperature. To fill polyamide with suitable mass percentage of PTFE can effectively reduce the viscosity of blend, and as a result, the molding and processing properties are improved.展开更多
PA6/PTFE blends with varying polytetrafluoroethylene content from 3% to 15%(mass fraction) were irradiated by 60Co gamma-ray with various doses(20,50 and 100 kGy) under ambient conditions.Moisture absorption test,U-no...PA6/PTFE blends with varying polytetrafluoroethylene content from 3% to 15%(mass fraction) were irradiated by 60Co gamma-ray with various doses(20,50 and 100 kGy) under ambient conditions.Moisture absorption test,U-notched Charpy impact test and quasi-static tension and bending were conducted to investigate the effect of irradiation on moisture absorption and mechanical properties of the blends.It is shown that the exposure of the blend to 60Co irradiation improves the tensile modulus,tensile strength and flexural modulus due to irradiation induced cross-linking in PA6 phase.However,the Charpy impact strength of the blends is much lower than that of the original PA6 and it decreases slightly with the increase of irradiation dose.Moreover,the flexural modulus increases to a maximum value and then decreases with further increasing the PTFE content,and the moisture absorption decreases with the increase of the PTFE content and irradiation dose.展开更多
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Prqject(10572123) supported by the National Natural Science Foundation of China Project(05JJ30014) supported by the Natural Science Foundation of Hunan Province, China Project(05C100) supported by the Scientific Research Fund of Education Department of Hunan Province, China
文摘The effects of polytetrafluoroethylene (PTFE) content on water-absorptivity, tensile strength, flexural strength, and notched impact strength of polytetrafluoroethylene/polyamide 6 (PTFE/PA6) and polytetrafluoroethylene/polyamide 66 (PTFE/PA66) blends were investigated by water immersion test, uniaxial tensile test, three-point test, and Charpy impact fracture test. The water-absorptivity in the blend decreases with increasing PTFE content, which indicates that the PTFE phase restrains the polyamide phase from water absorption. For water-free blends, the addition of PTFE causes a reduction in tensile strength, while for water-absorbed PTFE/PA6 blends, the tensile strength increases with increasing PTFE. Simultaneously, the absorbed water improves the elongation, but results in a notable reduction in flexural strength of the blends. Although the addition of PTFE causes a reduction in notched impact strength of the blends, as compared to pure polyamide, the absorbed water has little effects on the notched impact strength of the blends. Finally, the effects of temperature and loading frequency on complex viscosity parameters of PTFE/PA6 and PTFE/PA66 melts were tested. It is found that the complex viscosity of PTFE/PA6 melt is reversed with increasing temperature and shear velocity, but that of PTFE/PA66 melt increases approximately in exponential form with increasing temperature. To fill polyamide with suitable mass percentage of PTFE can effectively reduce the viscosity of blend, and as a result, the molding and processing properties are improved.
基金Project(10772156) supported by the National Natural Science Foundation of ChinaProject supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China
文摘PA6/PTFE blends with varying polytetrafluoroethylene content from 3% to 15%(mass fraction) were irradiated by 60Co gamma-ray with various doses(20,50 and 100 kGy) under ambient conditions.Moisture absorption test,U-notched Charpy impact test and quasi-static tension and bending were conducted to investigate the effect of irradiation on moisture absorption and mechanical properties of the blends.It is shown that the exposure of the blend to 60Co irradiation improves the tensile modulus,tensile strength and flexural modulus due to irradiation induced cross-linking in PA6 phase.However,the Charpy impact strength of the blends is much lower than that of the original PA6 and it decreases slightly with the increase of irradiation dose.Moreover,the flexural modulus increases to a maximum value and then decreases with further increasing the PTFE content,and the moisture absorption decreases with the increase of the PTFE content and irradiation dose.
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.
