Extensional Flow Behavior of Methylcellulose Solutions Containing Fibrils

Abstract

The extensional properties of semidilute aqueous methylcellulose (MC) solutions have been characterized. Pure aqueous MC solutions are shear-thinning liquids at room temperature. With the addition of 8 wt % NaCl, a fraction of MC self-assembles into long fibrils, which modify the rheological properties of the original MC solution. Capillary Breakup Extensional Rheometry (CaBER) was used to characterize salt-free and 8 wt % NaCl solutions of MC at room temperature. The salt-free solutions exhibit only power-law behavior whereas solutions with NaCl exhibit both power-law and elastic regimes. As MC concentration increases, the extensional relaxation time also increases strongly, from 0.04 s at 0.5 wt % to 4 s at 1 wt %. In addition, the apparent extensional viscosity rapidly increases as a function of increasing MC concentration, from 40 Pa•s at 0.5 wt % to 1300 Pa•s at 1 wt %. This behavior is attributed to the presence of fibrils in the MC solutions containing NaCl.

Homogeneous gelation leads to nanowire forests in the transition between electrospray and electrospinning

“…[26][27][28] Also relevant to the ESD process is that, once formed, the fibril network is shear thickening 29 and highly viscous in extension. 30 Prior kinetic investigations have shown three characteristic time scales for MC gelation, 31 with the most rapid potentially satisfying the required kinetics.…”

Rheology and Pinching Dynamics of Associative Polysaccharide Solutions

“…DoS rheometry relies on the analysis of pinching dynamics using radius evolution data, in analogy with other capillarity-based techniques, like capillary break-up extensional rheometer (CaBER) and other devices that rely on necks formed by applying step-strain to liquid bridges confined between two parallel plates, ,− ,,− or dripping, − or jetting-based rheometry. ,,− Analysis of pinching dynamics is increasingly preferred for evaluating extensional rheology response at rates and conditions similar to drop formation and coating processes. However, as the commercially available CaBER (and its variants) analyzes the pinching dynamics of the neck created by applying step-strain to liquid confined between two parallel plates, two well-documented problems arise.…”

Methylcellulose–Cellulose Nanocrystal Composites for Optomechanically Tunable Hydrogels and Fibers

“…60% and a rather constant and persistent diameter of ~15 nm, which has been confirmed and visualized both experimentally (cryo-TEM imaging, and small angle neutron and X-ray scattering) and via computational simulations ( Figure 2 ) [ 57 , 58 , 59 , 60 , 61 , 62 , 63 ]. Additionally, fibril formation may be induced by the addition of salt [ 64 , 65 ]. Rather recently, the tightly packed core region of the fibers has been suggested to comprise semicrystalline twisted MC chain domains aligned along the fibril long axis and surrounded by amorphous and less-ordered regions [ 66 ].…”