Characterization of Autocatalytic Reactions in Modified Cellulose/NMMO Solutions by Thermal Analysis and UV/VIS Spectroscopy

Abstract

The thermal stability of cellulose/N-methylmorpholine-N-oxide (NMMO) solutions were investigated using UV/VIS spectrometry with a temperature programming cuvette and caloric measurements by means of the Systag calorimeter RADEX (mini-autoclave). Both analytical methods allow to characterize the influences of stabilizers and additives. With the temporal course of the optical density, temperature and pressure thermal runaway reactions with gas evolution and accumulation of chromophoric degradation products were recognized. Kinetic model calculations compared with UV/VIS measurements demonstrate the existence of autocatalytic reactions in cellulose/NMMO solutions. Varying the heating rate autocatalysis can be proved by dynamic caloric measurements as well.

Sulfated cellulose thin films with antithrombin affinity

“…The C1s spectrum deviates from the typical shape expected for cellulosic materials, however similar spectra were previously obtained for and remaining anhydride groups of PEMA were assigned to component peak D. The two component peaks B and C mainly reflect the C-OH and C-O-C (B) and acetal groups of cellulose (C). Autocatalytic degradation of cellulose in NMMO solutions is described in the literature [22]; oxidized cellulose species, such as keto groups are produced and contribute to the component peaks C as well. The corresponding S 2p spectrum does not show any traces of sulfur.…”

Cellulose modification and shaping – a review

“…However, a major drawback is that the N-O bond is very energy rich, which means that NMMO is thermally unstable. It is also sensitive to catalytic impurities, which could result in unwanted sidereactions [32][33][34].…”

Thermal Stability of Lyocell Solutions: Experimental Results and Modeling Using Cluster Analysis and Partial Least Squares Regression

“…[11] The N-methylmorpholiniumyl radical and N-(methylene)morpholinium cation are formed, which are very unstable and highly reactive intermediates and enter into subsequent reactions, possibly autocatalytic ones. [11,12] Especially in the presence of functional additives, a variety of additional by-products may appear.…”

“…Analytical investigations of Lyocell dopes with regard to the thermostability are commonly made by rheological, calorimetric and spectroscopic methods. [7,[11][12][13][14] In particular, the measurements of the pressure gradient and the generation of chromophores give information about the temporal behavior of the sample surrounded by a constant temperature. These methods are generally complex and timeconsuming and only available after preparing the cellulose/ NMMO solution.…”

“…[12] Approximately 2 g of the cellulose/ NMMO solution were applied. Scanning measurements were provided by heating the vessel with a heating rate of 0.75 K Á min…”