This study presents results that show that the fine structure of arabinoxylan affects its interaction with cellulosic surfaces, an important understanding when designing and evaluating properties of xylan-cellulose-based materials. Arabinoxylan samples, with well-defined structures, were prepared from a wheat flour arabinoxylan with targeted enzymatic hydrolysis. Turbidity measurements and analyses using NMR diffusometry showed that the solubility and the hydrodynamic properties of arabinoxylan are determined not only by the degree of substitution but also by the substitution pattern. On the basis of results obtained from adsorption experiments on microcrystalline cellulose particles and on cellulosic model surfaces investigated with quartz crystal microbalance with dissipation monitoring, it was also found that arabinoxylan adsorbs irreversibly on cellulosic surfaces and that the adsorption characteristics, as well as the properties of the adsorbed layer, are controlled by the fine structure of the xylan molecule.

Most textile waste is either incinerated or landfilled today, yet, the material could instead be recycled through chemical recycling to new high-quality textiles. A first important step is separation since chemical recycling of textiles requires pure streams. The focus of this paper is on the separation of cotton and PET (poly(ethylene terephthalate), polyester) from mixed textiles, so called polycotton. Polycotton is one of the most common materials in service textiles used in sheets and towels at hospitals and hotels. A straightforward process using 5-15 wt% NaOH in water and temperature in the range between 70 and 90°C for the hydrolysis of PET was evaluated on the lab-scale. In the process, the PET was degraded to terephthalic acid (TPA) and ethylene glycol (EG). Three product streams were generated from the process. First is the cotton; second, the TPA; and, third, the filtrate containing EG and the process chemicals. The end products and the extent of PET degradation were characterized using light microscopy, UV-spectroscopy, and ATR FT-IR spectroscopy, as well as solution and solid-state NMR spectroscopy. Furthermore, the cotton cellulose degradation was evaluated by analyzing the intrinsic viscosity of the cotton cellulose. The findings show that with the addition of a phase transfer catalyst (benzyltributylammonium chloride (BTBAC)), PET hydrolysis in 10% NaOH solution at 90°C can be completed within 40 min. Analysis of the degraded PET with NMR spectroscopy showed that no contaminants remained in the recovered TPA, and that the filtrate mainly contained EG and BTBAC (when added). The yield of the cotton cellulose was high, up to 97%, depending on how long the samples were treated. The findings also showed that the separation can be performed without the phase transfer catalyst; however, this requires longer treatment times, which results in more cellulose degradation.

The textile industry is currently under pressure to decrease environmental load related to both the manufacture and the use of textiles. Material recycling may be one of many ways to accomplish such a decrease. Age-induced property changes in cotton textiles are important to understand in order to facilitate the recycling of cotton textiles. Consequently, this study investigates ultrastructural and chemical changes that take place in the cellulose of cotton sheets over a long time period of use and laundering. Ultrastructural changes were studied using water retention value (WRV), specific surface area measurement, scanning electron microscopy and solid state NMR spectroscopy. Chemical changes through measurement of intrinsic viscosity with and without reductive treatment, molecular mass distribution and carboxylate group content. A substantial decrease in mass average molecular mass from 1,320 to 151 kDa was observed when subjecting the sheets to more than 50 launderings. In contrast, only small differences in WRV, in fibril dimensions and crystallinity estimated using solid state NMR spectra, were observed between sheets laundered 2-4 times and more than 50 times. On one hand, the combination of minor laundering effects of WRV and solid state NMR spectra, together with the large decrease in molecular mass are positive indications for the possibility of recycling cotton into regenerated cellulosic fibres. On the other hand, results show that the specific surface area decreased, which implies that the reactivity of cotton cellulose may decrease during long-term use and laundering.

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The behaviour of different cellulosic fibres during acid hydrolysis has been investigated and the levelling-off degree of polymerisation (LODP) has been determined. The study included a bleached kraft pulp (both never-dried and once-dried) and two dissolving pulps (once-dried). Additionally, cotton cellulose from new cotton sheets and sheets discarded after long-time use was studied. Experimental results from the investigation, together with results found in literature, imply that ultrastructural differences between different fibres affect their susceptibility towards acid hydrolysis. Drying of a bleached kraft pulp was found to enhance the rate of acid hydrolysis and also result in a decrease in LODP. This implies that the susceptibility of cellulosic fibres towards acid hydrolysis is affected by drying-induced stresses in the cellulose chains. In cotton cellulose, it was found that use and laundering gave a substantial loss in the degree of polymerisation (DP), but that the LODP was only marginally affected.