Research On The Influence Of Molecular Chain Entanglement And Additives On The Rheological Behavior Of PAN/DMSO Solution

Carbon fibers prepared from polyacrylonitrile?PAN?precursors have excellent properties such as high strength and high modulus,and have been widely used in the field of modern science and technology.At the same time,the performance of PAN fibers depends to a large extent on the properties of the spinning solution.So the preparation of a homogeneous PAN solution with good rheological stability is an important prerequisite for the preparation of high-performance PAN fibers.Many external factors will affect the rheological stability of the spinning solution.Therefore,in this paper,a series of PAN/DMSO solutions were prepared using dimethyl sulfoxide?DMSO?as the solvent.The effects of test temperature,solution concentration,shear strength,and types and amounts of additives on the rheological behavior of PAN/DMSO solution were discussed.Fourier transform infrared spectroscopy?FTIR?was used to analyze the complex state and influencing factors of solute and solvent in PAN/DMSO solution.The specific results are as follows:?1?The effects of temperature,concentration and shear on the entanglement of PAN molecular chains in PAN/DMSO solution were studied through rheological tests.The steady state test results show that pre-shearing can effectively remove part of the PAN molecular chain entanglements.At the same time,as the shearing effect increases,the PAN molecular chain untangling and orientation effect increase.The physical entanglement and unentanglement caused by coupling between cyano groups is a dynamic equilibrium process.Reducing the shear rate,increasing the temperature,and reducing the concentration of the PAN/DMSO solution are conducive to enhancing the entanglement reconstruction of the PAN molecular chain.Enhance the rheological stability of PAN/DMSO solution.Both temperature increase and concentration decrease can reduce the molecular chain entanglements in the PAN/DMSO solution and reduce the viscoelastic behavior of the PAN/DMSO solution.?2?The DMSO and PAN/DMSO solutions containing ammonium chloride?NH₄Cl?and urea?CO?NH₂?₂?were analyzed by FTIR.The results show that the addition of NH₄Cl and CO?NH₂?₂ can slow down the self-association state of DMSO destruction;the presence of a small amount?2 wt%?of NH₄Cl is conducive to the interaction between DMSO and the cyano group in the PAN molecule,reducing the viscosity of the solution.Continue to increase the amount of NH₄Cl or use CO?NH₂?₂ as an additive will destroy the complex between DMSO and cyano group,resulting in an increase in solution viscosity.