Material PropertiesDynamic viscosity of maleate poly(vinyl alcohol) and its copolymer measured by rheometer

The objective of this work was to study the mechanism of gel formation for maleated poly(vinyl alcohol) (PVAM) and maleated poly(vinyl alcohol)-graft-gelatin (PVAM-g-GT) in solution form using a rheometer to monitor changes in the dynamic viscosity and shear stress-shear rate curves. The dynamic viscosity of the PVAM solution increased and then decreased with increases in the shear rate, and the dynamic viscosity of the PVAM solution decreased as a function of the MA content increased. The dynamic viscosity of the PVA solution was higher than that of the PVAM solution due to its gel formation. Moreover, the dynamic viscosity of the PVAM solution increased and then decreased over long periods. Over a storage time of 2 days, the dynamic viscosity of the PVAM decreased due to chain scission. The PVAM solution showed shear thickening in the first stage and shear thinning in the last stage of the experiment. The dynamic viscosity of the PVAM-g-GT solution continued to decrease continually at a constant rate with increases in the shear rate because the H-bonding was broken at higher shear rates. This was probably because the energy of the H-bonding interaction is less than the energy of carbon-carbon covalent bonding resulting in broken H-bonding both intra-chain and inter-chain H-bond.