Lenzing Lyocell - a versatile fiber
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Lenzing Lyocell – a versatile fiber D.Eichinger, H.Firgo and Ch.Rohrer Lenzing AG, A-4860 Lenzing, Austria www.lenzing.com
MAN MADE CELLULOSIC FIBRES Cellulosics have a very balanced set of general features, with its unique specific control of moisture resulting in widely accepted physiological benefits and wearing comfort. This gives interesting future prospects for the man-made cellulosics Viscose, Modal and Lyocell by Lenzing AG. The fibres produced cover a wide range of nowadays possibilities from the viscose and Lyocell process, covering textile, non woven, technical or medical application. For a brief introduction into the different types some of the main properties are given in table 1 compared with other fibres. Table 1: properties of man made cellulosic fibres compared with cotton tenacity dry tenacity wet tenacity wet/dry*100 elongation dry elongation wet modulus dry wet modulus (bisfa) loop tenacity loop elongation knot tenacity
cN/tex cN/tex % % % cN/tex cN/tex cN/tex cN/tex cN/tex
Viscose
Modal
Lyocell
Cotton
24-26 10-13 50 18-20 21-23 4-5 2-3 7-8 3-5 13-15
34-36 19-21 55-60 12-14 13-15
40-42 34-36 85 15-17 17-19 6-12 8-10 16-26 3-5 25-31
24-36 26-40 105-110 7-9 12 4,5 6-10 20-26 5-7 30
5-6 7-8 2-3 17
Based on the table it is easily understood that a lot progress has been made from the early beginning of man made cellulosic fibres to modify mechanical properties via optimisation of structure during manufacturing process or via the type of process. The different behaviour of the known types of cellulosic fibres is also found in structural parameters measured by scattering methods as well as by size exclusion chromatography or water retain values. Table 2: Structural parameters of different cellulosic fibres1,2 Parameter
unit
Viscose
Modal
degree of polymerisation Crystalinity IO void volume Inner surface BET surface mean pore diameter
DPw
200-250 0,39 0,68 444 276 31
400-600 0,39 0,49 407 277 23
ml/g m2/g m2/g Angstrom
U2.2.1
Lyocell 600-800 0,62 0,60 418 246 28-30
Cotton
2000 0,74 0,30 207 132 28
0,70 void volume by inverse size exclusion chromatography 0,60
V [ml/g]
0,50 0,40 0,30
Viskose Modal Lyocell
0,20 Dextran Mw 1000, Hd 18
0,10 0,00 0
10
20 30 d [Angstrom]
40
50
Fig. 1: pore size via inverse size exclusion chromatography of viscose, modal and Lyocell As seen from table 2 and fig. 1 the results of Viscose, Modal and Lyocell are very different, which is a result of the different structural system (in ISEC esp. seen on the interaction of the specific dextran molecule). Some of the differences result from the different skin properties, some are due to the inner pore system. The explanation given for Viscose is the pronounced tight skin/open core structure3. But common to all man made cellulosic fibers is the higher inner surface compared to cotton. One of the most important features of man made cellulosic fibres is their moisture regain and their capability to swell and retain aqueous liquids. Although well known nowadays it is seldom attributed as a special funct
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