Chemical and ultrastructural changes in cotton cellulose induced by laundering and textile use
Anna Palme
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1
2
Alexander Idstro m
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1
2
Lars Nordstierna
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1
2
Harald Brelid
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2
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H. Brelid Sodra Innovation, 432 86 Varobacka,
Sweden
1
A. Idstrom L. Nordstierna Division of Applied Surface Chemistry, Department of Chemical and Biological Engineering, Chalmers University of Technology
, 412 96 Gothenburg,
Sweden
2
A. Palme (&) Division of Forest Products and Chemical Engineering, Department of Chemical and Biological Engineering, Chalmers University of Technology
, 412 96 Gothenburg,
Sweden
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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Systems for collection and recycling of common
consumer goods, such as paper, plastics and glass are
well developed in many parts of the world today. One
product category which is still underdeveloped in
terms of recycling is clothing and textiles. The
lifecycle of a garment may be expanded through reuse,
but only if the garment still has good quality without
damages or stains. Garments and textiles that are not
suitable for reuse may be mechanically shredded and
used for products such as carpet underlays and
upholstery (Morley et al. 2006; Palm 2011). In order
to gain both economic and environmental benefits,
more efficient recycling of textiles is needed. Using
old cotton textiles as a raw material to produce
regenerated cellulosic fibres, such as viscose or
lyocell, is an attractive alternative end-of life scenario
in comparison to incineration or landfilling
(Negulescu et al. 1998). To enable this development, more
knowledge of changes induced by use and laundering
in post-consumer cotton textiles is needed.
The focus of this study is on ageing cotton textiles,
and the motivation, apart from the applied perspective,
is that understanding of this process will contribute to
more basic understanding of how cellulosic materials
age. The ageing of cellulose in paper has been
extensively investigated in applications such as
archiving of books (Wilson and Parks 1979) and the
recycling of paper (Hubbe et al. 2007). Books or other
archived paper, produced under acid conditions, may
deteriorate rapidly through the acid hydrolysis of the
cellulose (Kato and Cameron 1999). In paper
recycling, the repeated drying and rewetting cycles lead to
a decrease in the swelling ability of chemical pulp
fibres. This change in swelling behaviour has been
defined as hornification by Jayme (1944; Weise 1998).
Today, the term hornification is used in a broader
sense to describe changes in chemical pulp fibres
attributed to drying, such as stiffer and less
conformable fibres (Hubbe et al. 2007). These changes are
associated with the non-reversible closing of
nanosized pores in the fibres during drying, due to
coalescence of cellulose fibril aggregates (Ponni
et al. 2012). The coalescence is often explained by
the formation of hydrogen bonds between the
cellulose fibril aggregates in the fibre walls, but
crosslinking reactions that lead to the formation of covalent
bonds have also been suggested (Hubbe et al. 2007;
Laivins and Scallan 1993). In addition, solid state
NMR studies have shown that co-crystallization
between cellulose fibrils is another possible reason
for the formation of bonds between fibril aggregates
(Idstro m et al. 2013; Newman 1999). Furthermore, the
closing of small pores and the increase in fibril
aggregate size will lead to a decrease in accessible
surface area.
A textile is subjected to numerous laundering
cycles during its life tim (...truncated)