Polyacrylonitrile (PAN) copolymers of different molecular weights were synthesized by a
suspension polymerization and precipitation polymerization method. The rheology behaviors
of the synthesized PAN copolymers were investigated in relation to their molecular weight,
solid content and melting temperature. The influence of “historical effects” on the spinning
solution of PAN was studied by analyzing the laws of viscosity considering the diversification
time and temperature. The viscosity disciplines of each spinning solution conformed well
to the rheological universal laws in a comparison of the suspension polymerization product
with that of precipitation polymerization. Viscosity changes in the swelling process of
dissolution were gentler in the suspension polymerization product; a small amount of water
will quickly debase the solution viscosity, and high-speed mixing can greatly shorten the
time required by the spinning solution to reach the final viscosity.