Effect Of Viscoelasticity Of PAN Concentrated Soluton On The Orientation And Mechanical Property Of Pan Precursor

Carbon fiber has been widely used in many fields because of its excellent mechanical properties.As the precursor of PAN based carbon fiber,the properties and quality of PAN precursor are the key to improve the mechanical properties of PAN based carbon fibers.The mechanical properties of precursors is closely related to fiber's orientation and regularity,the orientation structure of the fiber is formed in the process of drafting,so it is necessary to explore the influence factors of fiber's ability of drafting,study on the mechanical properties of PAN precursor fibers from fiber's ability of drawing.At present,there are few researches on the fiber's ability of drafting,some research had found of fiber's ability of drafting will be different with the changes of the polymerization conditions of spinning solution,and the structural factors that affect the tensile properties are not explored.As the object of drafting,the structure of the nascent fiber will inevitably affect fiber's ability of drawing.In addition to the influence of external factors such as temperature,concentration and drafting of the coagulation bath,the properties of the nascent fibers are also affected by the intrinsic properties of the spinning solution and its viscoelasticity.In this paper,based on the establishment of the relationship between the viscoelasticity of the spinning solution,the structure of nascent fiber,the fiber orientation,fiber orientation and mechanical properties,the following conclusions are drawn:1?The skin core structure,porosity,homogeneity and crystallinity of the primary fiber will affect the fiber's ability of drawing.The influence of the structure of the nascent fiber obtained by the coagulation bath temperature on the fiber drawing is the same as that of the coagulation bath.The structure that influences fiber's ability of drawing will inherit and inherit during spinning,and then induce the fiber to be stretched at the high pressure steam draft.2?There is a negative correlation between the viscosity of spinning liquid and the draft of its primary fiber.In many factors,the increase of crystallinity is the main reason for the decrease of fiber drawing property.With the increase of spinning solution viscosity,spinning solution viscosity from 2000P to 2500P,the crystallinity of fiber increased rapidly and the drafting of the fiber spinning solution viscosity decreased;from 2500P to 5000P,the crystallinity of fiber increased and reduced fiber's drafting ability also declined.There is a similar negative correlation between the elasticity of spinning liquid and the draft property of the primary fiber.With the increase of elasticity,the crystallinity of the primary fiber increases and the draft decreases.3?Improve the hydrophilicity of PAN system,effectively reduce the phase transformation of solution in the process of solidification,is conducive to the self crystallization tendency of PAN molecules to form the obvious crystallization,thereby improving the spun fiber crystallinity of fiber drawing down.4?Different viscoelastic PAN solution during solidification under the same conditions with different drawing-orientation behavior,low viscosity solution system,not only has good fiber drafting performance,and its orientation with the draft showed continued steady growth.Under the same drawing conditions,the fibers with good drawing properties tend to have lower orientation and tensile modulus because of the low orientation efficiency.