Premium
Viscoelasticity of concentrated polyacrylonitrile solutions: effects of solution composition and temperature
Author(s) -
Tan Lianjiang,
Wan Ajun,
Pan Ding
Publication year - 2011
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.3041
Subject(s) - viscoelasticity , polyacrylonitrile , thixotropy , rheology , stress relaxation , materials science , creep , shear rate , shear stress , water content , elasticity (physics) , thermodynamics , composite material , polymer , geotechnical engineering , physics , engineering
The effects of solution composition and temperature on the viscoelasticity of concentrated polyacrylonitrile (PAN) solutions were studied using a variety of rheological measurements, such as steady‐state shearing, dynamic stress sweep and transient rheological tests. The first normal stress difference N 1 and the shear stress τ were found to increase with decreasing temperature and increasing PAN concentration and water content in the solutions. The crossover point of N 1 and τ, denoting the equal contribution of viscosity and elasticity to the viscoelasticity of the solutions, moved to lower shear rates at lower temperature, higher PAN concentration and higher water content. The values of the relaxation time (λ) were larger at 70 °C than at 40 °C. In addition, the changes of λ with PAN concentration and water content were different at the two temperatures, ascribed to the different states of the solutions. The PAN solutions were in the linear viscoelastic regime in the temperature range 40–70 °C when the shear stress was below 300 Pa. The creep compliance recovery rate decreased with increasing temperature, but increased with increasing PAN concentration and water content. Thixotropic tests showed that the thixotropy of the solutions was also affected by the solution composition and temperature. Gelation was found to influence the way the solution composition and temperature affected the viscoelastic properties of the PAN solutions. Copyright © 2011 Society of Chemical Industry