Effect of deaeration processing on the behavior of an acrylonitrile-acrylamide copolymer and carbon fiber precursors

The effect of the deaeration process on the behavior of acrylonitrile-acrylamide copolymer solutions was demonstrated experimentally in detail. The corresponding mechanical properties and morphology of the resultant precursors were also been examined. It was found that the viscosity of the copolymer solutions at rest increased continuously with the deaeration time prolonged at every fixed temperature stage, but it considerably increased when the deaeration temperature decreased. The changes in the viscosity of the solutions at 80 degrees C were less prominent than those of the solutions at 20 degrees C in the beginning stage; beyond 60 min, the changes became remarkable. In concentrated copolymer solutions, the dimethyl sulfoxide composition weight percentage decreased with an increase in the deaeration temperature; the increasing temperature reduced the solvent power continuously at a high deaeration temperature, so more solid-elastic gels were formed in the solutions with an increase in time. At the same degree of vacuum, when the temperature varied from 20 to 80 degrees C and, in particular, the deaeration temperature was beyond 60 degrees C, the products from the copolymer seemed to have slightly narrower molecular weight distributions. With the deaeration temperature increasing, the tensile strength, elongation at break, and bulk density of the resultant precursors increased, but their fineness and coefficient of variation decreased. The morphology of the precursors was more compact and more round beyond 60 degrees C than below 60 degrees C. (c) 2007 Wiley Periodicals, Inc.