Studies on the Stabilization of Modified Lyocell Solutions

Abstract

Additives with functional properties makes the Lyocell process a versatile tool for the creation of new innovative materials beyond the textile sector. Occupying functional groups or active surfaces the additives emphasize the suitability of Lyocell fibers, but simultaneously enhance the complexity of chemical reactions in cellulose/N‐methylmorpholine‐N‐oxide (NMMO) solutions, respectively. Concerning to the concentration acidic ion exchange resins, activated charcoals, carbon black etc. shift the start of decomposition to lower temperatures, decrease the viscosity, enhance the formation of amines as the main degradation products or cause autocatalytic reactions.New routes in stabilization of modified Lyocell solutions applying a polymeric stabilizer system are described. Using calorimetric, UV/VIS, ESR and HPLC analysis the degradation processes and thermal stability of modified Lyocell solutions compared to the unstabilized were studied. Moreover, as kinetic investigations show a distinguished behavior for modified solutions autocatalytic reactions can be suppressed by the stabilizing system. ESR kinetic study of radicals reveals that formation and recombination rates of radical reactions depend on cellulose concentration in Lyocell solutions and additional ingredients.

Cellulose solvent-based pretreatment for enhanced second-generation biofuel production: a review

“…374,377,[379][380][381] However, this technology has been recently introduced as a pretreatment method of lignocelluloses, e.g., for the improvement of either secondgeneration bioethanol 115,[382][383][384][385][386][387][388] or biogas production. [388][389][390][391][392][393][394][395][396][397] Having a strong N-O dipole, which acts as either an ionic or donative and single bond, NMMO is capable of disrupting the hydrogen-bond networks of cellulose and building new hydrogen bonds between the polymer and the solvent 375,379,398 (Fig. 10).…”

Ionic Liquids — Promising but Challenging Solvents for Homogeneous Derivatization of Cellulose

“…Onset temperatures (T on ) for the chemical decomposition and liberation of gaseous compounds around 180–220 °C have been observed and the values changed only slightly upon the addition of additives such as silver or activated charcoal particles. For comparison; cellulose/NMMO solutions are significantly less stable (T on ≈ 130–160) and require the addition of stabilizers in order to prevent autocatalytic thermal runaway reactions [ 139 , 140 ]. The efforts required for safe handling are a major drawback of NMMO, which is applied commercially for the fabrication of cellulosic Lyocell fibers.…”

Interactions of Ionic Liquids with Polysaccharides – 7: Thermal Stability of Cellulose in Ionic Liquids and N‐Methylmorpholine‐N‐oxide

“…Cellulose/NMMO solutions with and without additives give onset temperatures in the range of 130-160 8C. [25] Compared to DSC measurements, the miniautoclave measurements allow to differentiate much better resulting in a more accurate characterization of the influences of stabilizers and additives on the thermal behavior of the cellulose dissolved in different media. Dynamic measurements for the cellulose/NMMO solution reveal the typical exothermic temperature peak after S. Dorn, F. Wendler, F. Meister, T. Heinze The onset temperature (T on ) indicating the start of the thermal activity detected by the slope of pressure shows for both solutions differences.…”