The hydrolysis and recrystallisation of lyocell and comparative cellulosic fibres in solutions of mineral acid

Abstract

Regenerated cellulosic fibres undergo a process described as scission-reordering during hydrolysis in solutions of mineral acid. This occurs within disordered polymer regions at lateral crystal interfaces, which are accessible to aqueous agents through the pore spaces and polymer free volume. This process is distinct from that of oligomersolubilsation, which occurs within disordered polymer regions in series between crystal domains, where no effective template exists for recrystallisation. The degradation of series disorder will have the greatest influence on fibre tensile properties, which fall dramatically even at low levels of hydrolysis. The mechanics of fibrillation are most sensitive to the degradation of lateral disorder, which occurs at a higher rate constant. Soft-touch fabric processing may therefore be possible under conditions where there is a reduced influence on tensile performance. A kinetic model has been proposed to describe the hydrolysis and recrystallisation pathways, which shows that lyocell has longer but thinner crystal domains than viscose or modal fibres, and also a tighter distribution of lateral crystal sizes. Lyocell also has a lower proportion of series disorder and also thinner regions of lateral disorder. This is consistent with the overall greater crystallinity of the original lyocell fibre and the also of the final microscrystalline product.

Investigation into the removal of an easy-care crosslinking agent from cotton and the subsequent regeneration of lyocell-type fibres

“…7). The reduction in the degree of polymerisation was due to the degradation of cellulose polymer by scission of the glycosidic linkages between the pyranose rings of the amorphous fraction regions (Ibbett et al 2008). The breaking of the glycosidic linkages resulted in a loss of molecular weight and hence the degree of polymerisation of the cellulose.…”

“…With the closed loop system, the garment fabric that has reached the end of its ''first life'' could be collected, separated and then used as a raw material for regeneration of new fibres. The current option of reclamation of fibres from waste garments involves pulling out the fibres (shredding) and then spinning the separated strong fibres into yarn (Lebedev 1995;DEFRA 2006;Hirsch and Woodside 2002;Morel 1984;Ball and Hance 1994;Campman and Barbod 1970). However, the yarns spun from fibres obtained by the shredding process always have poorer mechanical properties and associated limitations (Lebedev 1995).…”

Towards understanding structural changes of photoperiod-sensitive sorghum biomass during sulfuric acid pretreatment

“…Crystallization of amorphous cellulose could be one reason for the increase in crystal size as found in the production of microcrystalline cellulose (Tang et al, 1996). A recent report also suggested the existence of templates of crystalline components at the dimension lateral to fiber direction (Ibbett et al, 2008); therefore, crystallization could begin at this dimension, resulting in the increase of crystal size in reflection (020). The increase in crystal size could lead to a decrease in the total surface area of cellulose, which might reduce chemical absorptions of cellulose fiber (Reddy and Yang, 2005) and might not be helpful for increasing the reaction rate of enzymatic hydrolysis.…”

Controlled thermo-catalytic modification of regenerated cellulosic fibres using magnesium chloride Lewis acid

“…The experimental Intensity versus 2h data was fitted to a simulated equatorial profile, with the parameters adjusted by least-squares non-linear minimisation using Microsoft Excel Solver TM (Ibbett et al 2008). A linear baseline was first subtracted from all experimental data sets, across the region of interest from 9 to 32°.…”