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Effect of mild alkali/ultrasound treatment on flax and hemp fibres: the different responses of the two substrates

Authors:
  • Óbuda University, Budapest, Hungary
  • Centre for Enery Research, Hungarian Academy of Sciences, Budapest, Hungary
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Abstract and Figures

Flax and hemp fibres were treated by various combinations of water/diluted alkaline solution and stirring/ultrasound, respectively. Changes in the microstructure (scanning electron microscopy) and porous structure (low-temperature nitrogen adsorption), removal of non-cellulosic materials (weight loss, FTIR), mean fibre diameter, and adhesion of the polypropylene matrix to the fibres (micro-bond test) were investigated. For both types of fibres, removal of (FTIR) was observed. The fibre diameter of hemp was decreased by several treatments, most of all by stirring in alkali and subsequent sonication in water, while the ultrasound applied in alkali solution did not change the fibre fineness. This can be attributed to the dual effect of ultra-sonication: the swelling effect of alkali combined with ultrasound energy probably served the sticking of inter-fibrillar material rather than their dissolution. Fibre diameter of flax did not change in any circumstances. The porosity of hemp in the mesopore range increased, while that of flax decreased by alkali treatment and subsequent sonication. The reason for this difference might be the dissimilar cell wall structures of the two bast fibres, the high arabinose content of the hemp, and/or the cottonisation of hemp. No treatments altered the fibre-matrix adhesion measured by pulling out the fibre from a micro-droplet of polypropylene.
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ORIGINAL PAPER
Effect of mild alkali/ultrasound treatment on flax and hemp
fibres: the different responses of the two substrates
Judit Borsa .Krisztina La
´szlo
´.Lydia Boguslavsky .Erzse
´bet Taka
´cs .
Ilona Ra
´cz .Tu
¨nde To
´th .Da
´vid Szabo
´
Received: 28 September 2015 / Accepted: 8 March 2016 / Published online: 18 March 2016
ÓSpringer Science+Business Media Dordrecht 2016
Abstract Flax and hemp fibres were treated by
various combinations of water/diluted alkaline solu-
tion and stirring/ultrasound, respectively. Changes in
the microstructure (scanning electron microscopy) and
porous structure (low-temperature nitrogen adsorp-
tion), removal of non-cellulosic materials (weight
loss, FTIR), mean fibre diameter, and adhesion of the
polypropylene matrix to the fibres (micro-bond test)
were investigated. For both types of fibres, removal of
(FTIR) was observed. The fibre diameter of hemp was
decreased by several treatments, most of all by stirring
in alkali and subsequent sonication in water, while the
ultrasound applied in alkali solution did not change the
fibre fineness. This can be attributed to the dual effect
of ultra-sonication: the swelling effect of alkali
combined with ultrasound energy probably served
the sticking of inter-fibrillar material rather than their
dissolution. Fibre diameter of flax did not change in
any circumstances. The porosity of hemp in the
mesopore range increased, while that of flax decreased
by alkali treatment and subsequent sonication. The
reason for this difference might be the dissimilar cell
wall structures of the two bast fibres, the high
arabinose content of the hemp, and/or the cottonisation
of hemp. No treatments altered the fibre-matrix
adhesion measured by pulling out the fibre from a
micro-droplet of polypropylene.
Keywords Flax Hemp Ultrasonic cleaning Fibre
diameter Porosity Nitrogen adsorption
Introduction
Cellulose and lignocellulosic materials as renewable
and biodegradable sources are being utilised for many
traditional and innovative purposes. Industrial hemp
and flax are very prosperous cellulose sources; they
provide important cellulosic and non-cellulosic sub-
stances (fibre, sieve, seed, and oil) with relatively low
agricultural investment. Their breeding and
J. Borsa (&)K. La
´szlo
´T. To
´th D. Szabo
´
Faculty of Chemical Technology and Biotechnology,
Budapest University of Technology and Economics,
Budapest 1521, Hungary
e-mail: borsa.judit@rkk.uni-obuda.hu
J. Borsa E. Taka
´cs
Rejt}
oSa
´ndor Faculty of Light Industry and Environmental
Engineering, O
´buda University, Budapest, Hungary
L. Boguslavsky
CSIR National Centre for Fibre, Textile and Clothing,
Port Elizabeth, South Africa
E. Taka
´cs
Centre for Energy Research, Institute for Energy Security
and Environmental Safety, Hungarian Academy of
Sciences, Budapest, Hungary
I. Ra
´cz
Furukawa Electric Institute of Technology, Budapest,
Hungary
123
Cellulose (2016) 23:2117–2128
DOI 10.1007/s10570-016-0909-y
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... † In the case of raw and degummed hemp bers, cellulose derived (1025 cm À1 ), O-H (3338 cm À1 ), and C-H (2917 cm À1 ) peaks are detected in both samples. 44,45 As expected, the lignin-related absorption is only conrmed in the raw-hemp ber around 1700-1500 cm À1 (yellow-shaded region), corresponding to aromatic skeletal vibration of C]C, conjugated C]O, and non-conjugated C]O. [44][45][46][47] For hydrothermal carbonized hemp ber, peaks of lignin including the aromatic ring (1610, 1508 cm À1 ), C-C/C-H of the syringyl unit (1380 cm À1 ), C-C/C-O of the guaiacyl unit (1211 cm À1 ), and phydroxyphenyl unit (834 cm À1 ) become noticeable due to loss of cellulose. ...
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