Dynamic viscoelastic properties of polyacrylonitrile(PAN)/DMSO/H2O solutions with different H2O contents were studied as a function of temperature.These PAN solutions gradually became gel with decreasing temperature.T...Dynamic viscoelastic properties of polyacrylonitrile(PAN)/DMSO/H2O solutions with different H2O contents were studied as a function of temperature.These PAN solutions gradually became gel with decreasing temperature.The sol-gel transition took place at a critical gel temperature,at which the scaling law of G'(ω)～G″(ω)∝ωn held,allowing an accurate determination of the critical gel temperature by means of the frequency independence of the loss tangent.The gel point of PAN solutions increases with increasing H2O content.The scaling exponent n(=0.86) at the gel point is confirmed to be universal for PAN gels,which is independent of temperature,suggesting the similarity of the fractal structure in the critical PAN gels.展开更多
For certain industrial applications, the mechanical properties of PET fiber can be deteriorated from hydrolysis because the terminal carboxylic groups promote the degradation of macromolecules under high moisture and ...For certain industrial applications, the mechanical properties of PET fiber can be deteriorated from hydrolysis because the terminal carboxylic groups promote the degradation of macromolecules under high moisture and high temperature. It limits the wide applications of PET fiber in some special cases. In this paper, three additives are selected to improve the hydrolytic stability through the reaction of bi-functional groups on additive molecules with carboxyl groups on PET molecules. The additives can serve not only as hydrolysis stabilizers, but also as agents to increase the molecular weight and consequently to improve PET fiber mechanical properties. PET pellets were blended with additive before spinning, and melt spun into fiber. The fibers were then hydrolyzed in an autoclave by saturated vapor at 140℃ for a period of time. Measurements of intrinsic viscosity, terminal carboxylic group value and strength of polyester fibers were carried out to study the effects of hydrolysis resistance. Results show that 2,2′-bis(2-oxazoline) has best hydrolysis-resistibility and the chain-extension effect at the same time.展开更多
基金Project(2006CB606505) supported by the National Basic Research Development Program of ChinaProject(50333050) supported by the National Natural Science Foundation of China+1 种基金Project(07DJ14002) supported by the Shanghai Fundamental Theory ProgramProject(20020255010) supported by the Specialized Research Fund for the Doctoral Program of Higher Education
文摘Dynamic viscoelastic properties of polyacrylonitrile(PAN)/DMSO/H2O solutions with different H2O contents were studied as a function of temperature.These PAN solutions gradually became gel with decreasing temperature.The sol-gel transition took place at a critical gel temperature,at which the scaling law of G'(ω)～G″(ω)∝ωn held,allowing an accurate determination of the critical gel temperature by means of the frequency independence of the loss tangent.The gel point of PAN solutions increases with increasing H2O content.The scaling exponent n(=0.86) at the gel point is confirmed to be universal for PAN gels,which is independent of temperature,suggesting the similarity of the fractal structure in the critical PAN gels.
文摘For certain industrial applications, the mechanical properties of PET fiber can be deteriorated from hydrolysis because the terminal carboxylic groups promote the degradation of macromolecules under high moisture and high temperature. It limits the wide applications of PET fiber in some special cases. In this paper, three additives are selected to improve the hydrolytic stability through the reaction of bi-functional groups on additive molecules with carboxyl groups on PET molecules. The additives can serve not only as hydrolysis stabilizers, but also as agents to increase the molecular weight and consequently to improve PET fiber mechanical properties. PET pellets were blended with additive before spinning, and melt spun into fiber. The fibers were then hydrolyzed in an autoclave by saturated vapor at 140℃ for a period of time. Measurements of intrinsic viscosity, terminal carboxylic group value and strength of polyester fibers were carried out to study the effects of hydrolysis resistance. Results show that 2,2′-bis(2-oxazoline) has best hydrolysis-resistibility and the chain-extension effect at the same time.
