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Temperature and shear dependencies of rheology of poly(acrylonitrile‐ co ‐itaconic acid) dope in DMF
Author(s) -
Devasia Renjith,
Nair C. P. Reghunadhan,
Ninan K. N.
Publication year - 2008
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1193
Subject(s) - shear rate , itaconic acid , activation energy , materials science , arrhenius equation , rheology , acrylonitrile , polymer , thermodynamics , polymer chemistry , atmospheric temperature range , viscosity , intrinsic viscosity , chemistry , composite material , physics , copolymer
Abstract Poly(acrylonitrile‐ co ‐itaconic acid) (poly(AN‐ co ‐IA)) precursor required for carbon fiber production is made into a dope and spun into fibers using a suitable spinning technique. The viscosity of the resin dope is decided by the polymer concentration, polymer molecular weight, temperature, and shear force. The shear rheology of concentrated poly(AN‐ co ‐IA) polymer solutions in N , N ‐dimethylformamide (DMF), in the $\overline M_{\rm v} $ range of 1 × 10 5 –1 × 10 6 g mol −1 , has been investigated in the shear rate (γ′) range of 1 × 10 1 –5 × 10 4 min −1 . The zero shear viscosity (η 0 ) has been evaluated at different temperatures. The temperature dependence of zero shear viscosity conformed to the Arrhenius–Frenkel–Eyring model. The free energy of activation of viscous flow (Δ G V ) values were in the range 5–32 kJ mol −1 and this value increased with increase in polymer concentration and molecular weight. A master equation for the Δ G V value of the polymer solution of any $\overline M_{\rm v} $ and concentration ( c ) is suggested. The power law $(\tau \, = \,k\gamma ^n )$ fitted well for the shear dependency of viscosity of these polymer solutions. The pseudoplasticity index ( n ) diminished with increase in polymer concentration and molecular weight. An empirical relation between viscosity (η) and $\overline M_{\rm v} $ was found to exist at constant shear rate, concentration and temperature. For each $\overline M _{\rm v} $ , the equation relating n , c , and T was established. Copyright © 2008 John Wiley & Sons, Ltd.