Flow Instability of Poly(vinyl alcohol)/Dimethyl Sulfoxide Solution under Steady Shear
- Flow Instability of Poly(vinyl alcohol)/Dimethyl Sulfoxide Solution under Steady Shear
- 주상우; 도성열; 류창열[류창열]; 노석균; 이용록; 심재진; 김준호; Yeong Soon Gal[Yeong Soon Gal]; 한성수; 류원석
- SOL-GEL TRANSITION; MOLECULAR-WEIGHT; RHEOLOGICAL PROPERTIES; VINYL PIVALATE; ALCOHOL); TEMPERATURE; POLYMERIZATION; POINT
- Issue Date
- POLYMERS & POLYMER COMPOSITES, v.19, no.6, pp.451 - 458
- 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(n)): 1700 and 4000. For the rheological experiments using dynamic shear, the PVA solution with a P(n) of 1700 showed rather simple Newtonian fluid behaviour, whereas that with P(n) of 4000 exhibited non-Newtonian shear thinning behaviour. Steady shear rheology experiments suggested that the lower P(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(n) PVA solutions at lower temperatures, such as 30 degrees C and 50 degrees C. At higher temperatures of 70 degrees C and 90 degrees 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(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.
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