Swelling and dissolution mechanisms of regenerated Lyocell cellulose fibers

Abstract

International audienceThe swelling and dissolution mechanisms of dry, never-dried and re-wetted Lyocell fibers were investigated using mixtures of N-methylmorpholine N-oxide and water with various contents of water (from monohydrate to 24% w/w). A radial dissolution starting from the outer layers was observed. Dissolution kinetics was dependent on the water content, the drying state and the spinning conditions. A buckling of the core of dry fibers was observed during swelling. This phenomenon was attributed to the deformation of the unswollen core to accommodate the contraction of the swollen parts of the fiber. In purely swelling conditions with no dissolution, a huge swelling of a very thin skin layer was observed in the first stage, followed then by a progressive swelling of the inside of the fiber. We postulate that this mechanism arose from the fact that this skin is much less crystalline than the core

Stress transfer in microfibrillated cellulose reinforced poly(vinyl alcohol) composites

“…This is due to the fact that when lyocell fibres, a highly oriented crystalline material, are under mechanical stress in a wet condition, the intra-hydrogen bonds between cellulose chains in the crystalline regions are easily broken. This allows fibrillation to occur, a well-known phenomenon for lyocell [36][37][38][39]. Therefore, as the treatment time used to fibrillate the lyocell fibres increases, the fraction of fibrils with diameter less than 500 nm increases [40,41].…”

First report on the kinetics of the uncatalyzed esterification of cellulose under homogeneous reaction conditions: a rationale for the effect of carboxylic acid anhydride chain-length on the degree of biopolymer substitution

“…Solvents that physically dissolve cellulose are of two kinds: (1) Ionic or strongly dipolar media, e.g., ionic liquids, and N-methyl-morpholine-N-oxide; (2) Solvent systems composed of a strong electrolyte dissolved in a dipolar aprotic solvent, e.g., LiCl/N,Ndimethylacetamide, DMAc, and quaternized ammonium fluorides in DMSO. Both media have generated intense interest because the dissolved biopolymer can be regenerated in different forms, or derivatized in a myriad of compounds, in particular, esters and ethers (Dawsey and McCormick 1990;El Seoud and Heinze 2005;El Seoud et al 2007;Heinze et al 2008a;Pinkert et al 2009;Eckelt et al 2009;Nagel and Heinze 2010;Dorn et al 2010;Schrems et al 2010;Chaudemanche and Navard 2011).…”

РЕОЛОГІЧНІ ВЛАСТИВОСТІ ТА ПЛІВКОУТВОРЮЮЧА ЗДАТНІСТЬ ПОЛІМЕРНИХ СУСПЕНЗІІЙ НА ОСНОВІ НАНОПОРОШКУ BaTiO3

“…всередину твердого полімеру [9,10]. При цьому взаємодія полімеру та розчинника супроводжується процесами сольватації та асоціації (структуроутворенням) [11,12], які призводять до формування структурної сітки з молекулярних зчеплень та переплутувань -«флуктуаційної» сітки, в якій міжмолекулярні зв'язки безперервно утворюються та руйнуються [13].…”