Extensional Flow Behavior of Aqueous Guar Gum Derivative Solutions by Capillary Breakup Elongational Rheometry (CaBER)
AbstractThe extensional rheological properties of aqueous ionic carboxymethyl hydroxypropyl guar gum (CMHPG) and non-ionic hydroxypropyl guar gum (HPG) solutions between the semi-dilute solution state and the concentrated network solution state were investigated by capillary breakup elongational rheometry (CaBER). Carboxymethylated guar gum derivatives show an instable filament formation in deionized water. The ratio of elongational relaxation time λE over the shear relaxation time λS follows a power law ofλE/λS∼(c⋅[η])−2λE/λS∼c⋅η−2. The difference of the relaxation times in shear and elongation can be related to the loss of entanglements and superstructures in elongational flows at higher strains.