Flow Instability of Poly(vinyl alcohol)/Dimethyl Sulfoxide Solution under Steady Shear

• Published in: Polymers & polymer composites 2011-01, Vol.19 (6), p.451-458
• Main Authors: Do, Sung Yeol, Ryu, Chang Yeol, Lee, Yong Rok, Shim, Jae Jin, Noh, Seok Kyun, Kim, Joon Ho, Joo, Sang Woo, Gal, Yeong Soon, Han, Sung Soo, Lyoo, Won Seok
• Format: Article
• Language: English
• Subjects: Alcohols; Applied sciences; Composition; Dimethyl sulfoxide; Dynamics; Exact sciences and technology; Hydrogen; Instability; Mechanical properties; Molecular weight; Organic polymers; Physicochemistry of polymers; Polymerization; Polyvinyl alcohol; Polyvinyl alcohols; Properties and characterization; Rheological properties; Rheology; Shear; Shear (Mechanics); Solution (Chemistry); Solution and gel properties; Stability; Temperature; Viscosity
• ISSN: 0967-3911; 1478-2391
• DOI: 10.1177/096739111101900602

The effects of solution temperature and molecular weight on the rheological responses of poly(vinyl alcohol) (PVA) semidilute solutions (13 g/dL - 19 g/dL) in dimethyl sulfoxide (DMSO) have been studied using PVA with two different number-average degrees of polymerization (P^sub n^): 1700 and 4000. For the rheological experiments using dynamic shear, the PVA solution with a P^sub n^ of 1700 showed rather simple Newtonian fluid behaviour, whereas that with P^sub n^ of 4000 exhibited non-Newtonian shear thinning behaviour. Steady shear rheology experiments suggested that the lower P^sub n^ PVA solutions were Newtonian fluids, which is consistent with the dynamic shear rheology results. However, an abrupt decrease of shear viscosity at high shear rates was observed for the higher P^sub n^ PVA solutions at lower temperatures, such as 30 °C and 50 °C. At higher temperatures of 70 °C and 90 °C, the higher molecular weight PVA solutions exhibited simple shear thinning behaviour without any further complications of flow instability. The fact that temperature plays a critical role in controlling the observed flow instability of the PVA solutions in DMSO strongly suggests that there exist enhanced inter-chain interactions by hydrogen bonding of PVA chains beyond the chain entanglements, particularly for the higher P^sub n^ PVA semidilute solutions at low temperatures. Therefore, it is important to consider both chain entanglements and hydrogen bonding interactions in order to process PVA solutions without causing undesirable flow instability. [PUBLICATION ABSTRACT]