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- Palme, Anna, 1986, et al.
(author)
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Acid hydrolysis of cellulosic fibres: Comparison of bleached kraft pulp, dissolving pulps and cotton textile cellulose
- 2016
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 136, s. 1281-1287
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Journal article (peer-reviewed)abstract
- 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.
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| 2. |
- Palme, Anna, 1986
(author)
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Recycling of cotton textiles: Characterization, pretreatment, and purification
- 2016
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Doctoral thesis (other academic/artistic)abstract
- In many parts of the world, there are well-established systems for material recycling of metal, glass, and paper. However, no large-scale chemical recycling of textiles currently exists. Since the collection of second hand textiles is established on a large-scale, one of the main barriers to obtaining chemical textile recycling is the development of recycling technology. Recently, it has been proposed that recycling cotton may be accomplished using post-consumer cotton to produce regenerated cellulose fibers, such as viscose and lyocell. These fibers are, today, made either from wood-derived dissolving pulp or cotton linters, both of which contain almost pure cellulose. The incorporation of used cotton fibers from textiles is an interesting possibility since cotton also contains almost pure cellulose. The most common textile material on the market contains a mix of polyester, i.e. poly(ethylene terephthalate) (PET), and cotton, referred to as polycotton, and the separation of the two components is necessary before recycling. This thesis investigates some important aspects of the chemical recycling of textiles. The focus is on four areas; property changes during laundering and use of cotton, acid pretreatment of cotton, swelling properties of cotton, and separation of cotton from polycotton textiles.The first part is based on that during the service life of cotton textiles, laundering is performed many times, and this may change the properties of cotton. When new cotton fibers are compared to cotton fibers from sheets that have been used in hospitals for a long period of time, findings show that laundering and use do not have a large impact on the supramolecular structure of cotton cellulose. However, the cellulose the degree of polymerization decrease greatly after long-term use.The second and third parts of the thesis investigate the pretreatment of cotton. Pretreatments of cellulose fibers are used to enhance susceptibility to dissolution before the production of regenerated fibers. Three different pretreatments were investigated, acid hydrolysis in water, acid hydrolysis in ethanol and hydrothermal treatment. Findings show that the degradation pattern is similar in cotton and dissolving pulp for all pretreatments.The last part of the thesis investigates the separation of the components in polycotton. In the process, polyester is hydrolyzed by the action of alkali while cotton is maintained. The process yields three product streams; two containing the two different monomers obtained when hydrolyzing the PET, and one with residual cotton. The yield of the process is high, and the fractions showed high purity.
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