Abstract
An experimental study of shear viscosity η(), principal normal stress difference N1(), storage modulus G′(ω), dynamic viscosity η′(ω), and filament elongation to break LB is reported for solutions of several polyamides; namely, nylon 66 in sulfuric acid (H2SO4) and formic acid (HCOOH), poly(γ-benzyl-L-glutamate) (PγBLG) in m-cresol, Nomex in H2SO4 and dimethylacetamide (DMA)/5% LiCl, and Kevlar in H2SO4 at 25 and 60°C. The variation of properties with concentration, polymer backbone and chain configuration, and solvent type is emphasized. The nylon 66/H2SO4 solutions have higher viscosity, normal stresses, and storage modulus than the HCOOH solutions of equivalent concentrations. The Nomex/H2SO4 solutions have higher viscosity and higher normal stresses and storage modulus than the DMA/LiCl solutions at equivalent concentrations. The significance of polymer chain backbone rigidity in forming liquid crystalline phases in Kevlar and PγBLG solutions is discussed and its influence on flow properties in indicated. These systems allow polarized light to pass through crossed polarizers and show maxima in viscosity–concentration data. The 25°C Kelvar solutions are distinctive in that they exhibit apparent yield stress values. This gives distinctive shear flow and oscillatory data. Filament elongation-to-break data show Kelvar > Nomex > nylon 66 in H2SO4 solutions for the order of spinnability.
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