We show that, above a critical stress, typical yield stress fluids (gels and clay suspensions) and soft glassy materials (colloidal glasses) start flowing abruptly and subsequently accelerate, leading to avalanches that are remarkably similar to those of granular materials. Rheometrical tests reveal that this is associated with a bifurcation in rheological behavior: for small stresses, the viscosity increases in time; the material eventually stops flowing. For slightly larger stresses the viscosity decreases continuously in time; the flow accelerates. Thus the viscosity jumps discontinuously to infinity at the critical stress. We propose a simple physical model capable of reproducing these effects.

http://absimage.aps.org/image/MAR05/MWS_MAR05-2004-002730.pdf

Avalanche behavior in yield stress fluids

Characterisation of gas mixing in water and pulp-suspension flow based on electrical resistance tomography

Experimental investigation on rheological, momentum and heat transfer characteristics of flowing fiber crop suspensions

Foundation Analysis and Design: A Case Study

Utilization of low-cost paper grade pulp is not feasible in Lyocell process due to presence of metallic and hemicellulose impurities that degrade cellulose and N-methyl-morpholine-N-oxide and lower the onset temperature of dope to initiate runway reaction. Conventional Lyocell process is restricted to use good quality dissolving grade pulp for safety reasons. To overcome this limitation, modified Lyocell process is demonstrated by pretreating pulps to remove metallic and hemicellulose impurities. Effectiveness of modified Lyocell process for faster dissolution and impurities removal for pulps/pulp blends is studied. Pretreatment of pulp blends significantly reduce impurities by 14–32% and improve swelling of pulp results in faster dissolution and safer process. Biopolymer prepared from modified process reduces undissolved particles by 50% and impurities by 30% thus improving overall quality and spinnability. This concept provides practical solution for using paper grade/impure pulps and making it more economical, faster dissolution and safe as compared to conventional process.

Modified Lyocell process to improve dissolution of cellulosic pulp and pulp blends in NMMO solvent

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Babak Derakhshandeh

Papers

Rheology of low to medium consistency pulp fibre suspensions