Technical Textiles Based on Regenerated Wool: Process and Test of a New Generation of Fabrics
The present study presents the main results of the Italian project Technical Wool, that was granted a subvention by the HI-TEX pilot Program 2007/2008 managed by Tuscany regional authority (Regione Toscana). The Technical Wool Project objective was to devise an innovative process able to confer to regenerated wool excellent properties in terms of dimensional stability, flammability and water repellence. The new process allows the creation of wool-based natural technical clothes. This new generation of fabrics may be considered considerably different from the conventional technical textiles, usually produced by means of artificial fibers. Moreover, while technical clothes are, generally, not fashion oriented, the secondary aim of the project was to confer to the new kind of textiles some aesthetic properties. The paper describes both the innovative process for producing some experimental fabrics and the tests performed for measuring some technical properties such as flammability, water repellence and dimensional stability. The results of the tests carried out on these, experimental, fabrics show that the devised process is suitable for producing technical clothes using regenerated wool as basis raw material. The Project involved four SMEs (Toscolaniera S.p.A. Filatura Safic S.r.l., New Mill S.p.A. a private research centre and Tessitura TAM S.r.l.) located on the Prato province, a well known Italian textiles and apparel district that is undergoing a deep economic and industrial crisis.
Technical textiles account for nearly 70% of textile industries product
in developed countries like the US, Japan and Europe. Global demand for technical
textiles will reach 85 billion dollars in a few years (Tewari,
2006). These encouraging data are attributable to a growing attention of
the customer to textile materials of new generation that are characterized by
high performances and that can be used not only when operating in technical
operations but also in everyday use. Thus, a key challenge for worldwide textiles
and clothing industry to remain competitive is to produce added value products
and develop new manufacturing technologies to meet increasingly demanding customer
requirements. Given that innovation in new materials, processes and products
is an inherent feature of this sub-sector, expenditure on R and D is higher
in this field than for conventional textiles (Holme, 2007).
In the development of fibers, yarns and fabrics, functional aspects - such as
thermal, or water proof functions-are playing an increasingly important role.
Since, technical textiles are generally not fashion oriented, performance requirements
and technical specifications determine the success of a product. Technical textiles
can be divided into many categories, depending on their end use. The classification
developed by Techtextil, Messe Frankfurt Exhibition GmbH is widely used in Europe,
North America and Asia (Liu et al., 2006) and
defines with the term Clothech (Clothing Textiles) the technical textiles for
clothing applications (Sung, 2009). Clothech consume
all kinds of fibers, i.e. natural fibers to high performance manmade fibers.
However, the manmade and inorganic fibers comprise of 79% of total fibre consumption
in technical textile applications as compared to 21% for natural fibers (Aizenshtein
and Efremov, 2006). A large number of studies have been carried out in the
last decades in the technical textiles field. An assessment of US comparative
advantage in technical textiles was developed by Chi et
al. (2005). The state of the art and the future challenges of the smart
textiles is provided in a study performed by Lymberis and
Paradiso (2008). Some comparative analysis of new materials used for advanced
technical woven fabrics, has been made by Ivana et al.
(2008). The use of regenerated or recycled fibers for realizing technical
clothes is deeply described in a work developed by Bartl
et al. (2005). According to the literature there is a need of using
regenerated wool in order to obtain natural technical clothes. The present work
describes the manufacture of technical fabrics characterized by a greater percentage
of natural fibers. Accordingly, in this context, during 2007/2008 the Technical
Wool Project experimented and tested a new process able to confer upgrading
performances to wool-based textiles, with particular attention to both some
technical properties and to aesthetic one. The Project was granted by HI TEX
pilot Programme of the Regione Toscana which aim is to promote and foster the
textile sector, focusing on quality and new approaches and to encourage the
growth of an entrepreneurial approach including research allowing interchange
of knowledge between companies. The Project involved four SMEs (Toscolaniera
S.p.A. Filatura Safic S.r.l., New Mill S.p.A. a private research centre and
Tessitura TAM S.r.l.) located on the Prato province, a well known Italian textiles
and apparel district that is undergoing a deep economic and industrial crisis
The main objective of the present work was to process and create a new generation
of textile with an high percentage of regenerated wool and described by some
technical properties. More in detail, this new generation of textiles has to
be typify by the following characteristics:
||Good dimensional stability: Shrinkage and shortening
have to be comprised into 3%
||Water proof: The fabrics have to be classified into class ISO 3
or higher according to the international standard EN 24920:1993
||Fire proof: The fabrics have to be classified in Class 1 according
to the standard C.F.R. PART 1610
||Good aesthetic properties
A fabric that satisfy the requirements may be considered a valuable Clotech.
Moreover, the use of a large quantity of natural fibers confers some aesthetic
and comfortable properties to the fabrics such as a better hand and softness.
MATERIALS AND METHODS
In order to obtain a new generation of Clothech the partners of the HI-TEX
project developed the following tasks during 2007-2008:
||Selection and production of wool-based yarns
||Weaving of the produced yarns
||Finishing of the weaved fabrics
||Test of the finished new generation of fabrics
Selection and production of wool-based yarns: The first step of the
project was to select and to produce a series of regenerated wool-based yarns
characterized by several technical properties. More in detail two kind of yarns
have been developed:
||Yarn composed by a mixture of regenerated wool and nylon
||Yarn composed by regenerated wool, nylon, viscose and cashmere
In the first case, some experimental tests performed by the New Mill laboratory,
showed that the best compromise between the technical properties of the yarns
and the capability of being spun can be reached with a wool fibre fineness comprised
into the range (19.5-23 μm), with an optimal value equal to 22 μm.
The use of a percentage of polyamide is required in order to increase the yarn
tenacity (Carvelli et al., 2008). In the second
kind of yarn developed by the technicians, the wool fibre fineness was set to
20.5 μm and the cashmere fibre fineness was set to 16.5 μm. Moreover,
a percentage of polyamide and viscose have been added to the mix in order to
improve the yarn performances. In Table 1 the composition,
tex, yarn strength, maximum elongation and fibre fineness of the two kinds of
yarns produced for the HI-TEX project are shown. In both cases the fibers have
been prepared by means of a standard process (bale opener, willowing machine,
carding willow and blow room) but with a modified lubrication (7% oil, 2% antistatic
agent, 6% water). The two kind of yarns described above have been selected among
a larger set of experimental yarns tested by the New Mill Laboratory. It is
evident that the results, in terms of yarn strength and fibre fineness are excellent
with regard to regenerated wool sector.
Weaving of the produced yarns: The two kind of yarn produced with the composition described in Table 1 have been used for producing a set of 7 weaved textiles. In Table 2, some properties of the 7 weaved textiles are shown. The textiles were weaved with different types of structure and in particular: Batavia, Plain Dobby and Dobby with several shafts.
||Composition, tex, yarn strength, maximum elongation and fibre
fineness of the two kinds of yarns produced for the HI-TEX project
||Structure, height and weight properties of the 7 weaved textiles
obtained, respectively, with yarns X171C (first three) and X931C (remaining
||Loom efficiency and speed for weaving the 7 prototypes. The
loom inactivity, the number of warp yarns and the density are also listed
A Vamatex Weaving Loom (Seyam, 2000) was used for weaving
the textiles. The high resistance of the yarn allowed to setup a high number
of strokes per minute, equal to 400-450. As wide known and further demonstrated
by Lord and Mohamed (1992) in order to reach an optimal
weaving speed, yarn friction and fibre shedding must be decreased while yarn
smoothness must be increased. The yarn smoothness may be described in terms
of weaving loom efficiency: a good smoothness is reached when the loom is characterized
by high efficiency (>90%) when working with high strokes per minute. In Table
3 the loom efficiency for weaving the 7 prototypes is showed. The number
of minutes per hour in which the loom remains inactive is also indicated. Since,
the object of the project was to realize technical textiles, another important
parameter that has to be considered by the technicians is the textile density,
expressed as the ratio between the number of warp yarn and the total weight
of the fabric. When this ratio is equal or greater than 6.5, the fabric may
be considered as a compact one. Table 3 shows that the selected
yarns have a good smoothness; moreover in the Table 3 the
textile density of the 7 prototypes is also showed.
Finishing of the weaved textiles: Once weaved, the fabrics have to be finished in order to confer some technical properties such as fireproof, waterproof and shrink proof.
The finishing phases adopted by the technicians, wide known in the state of
the art, are the followings (Vinzanekar et al., 1996):
||Washing and drying with tenter frame: The fabric is
held firmly at the edges by pins or clips on the two chains that diverge
as they advance through the heated chamber, adjusting the fabric to the
||Decatizing: The fabric, wound tightly on a perforated roller, has
steam blown through it. The process is aimed chiefly at improving the hand
and removing wrinkles
||Textile chlorination: The fabrics are treated with chloral, hypochlorite
and dichloroisocyanuric acid with 3-4% on mass of fibre (omf), at pH 10
and a temperature of 20-40°C. This treatment, that lasts 1 h, allows
the improvement of the dyeing affinity
||Polytetrafluoroethylene coating (Da-Yeon et
al., 2009): The fabrics are coated with Teflon in order to confer
both waterproof characteristics and an increased resistance to the effect
of high temperatures and corrosive chemicals. Moreover, the Teflon treated
fabrics shows a low frictional coefficient and a slippery hand. The coating
has been applied to the fabrics with an amount of 60 g L-1 of
The 7 fabrics used as a test set of the whole set of produced and finished
textiles have been tested in order to assess their technical properties. Specifically,
three kind of test have been performed on the fabrics: 1) dimensional stability
after subsequent washing and drying cycles, 2) water repellent capabilities
and 3) flammability.
||Results of relaxation shrinkage of warp and weft before and
after ironing for the 7 fabrics obtained with the 2 kinds of new yarns
Dimensional stability was assessed according to international standard EN ISO
6330:2002 using an horizontal rotating washing machine. The washing temperature
was maintained to 40°C. The ironing is performed at the temperature of 110°C.
The dry mass of each specimen is 2±0.1 kg and a cotton ballast was used
during washing. As described in the normative, the dimensional stability is
expressed in terms of shortening and shrinkage; the two parameters were measured
before and after ironing. Results of relaxation shrinkage of warp and weft are
shown in Fig. 1. As wide known shrinkage and shortening values
less than 3% may be considered valuable for technical textiles (Savile,
The water repellent capabilities have been assessed by measuring the resistance
to surface wetting by means of a spray test. The test was performed according
to the international standard EN 24920:1993. As widely known (Minazio,
1995) this standard defines 5 indexes (ISO 1, ISO 2, ..., ISO 5) each one
corresponding to a specific value of the AATCC (American Association of Textile
Chemists and Colourists) photographic scale (Weaver, 1984).
The higher is the value of the ISO index and the higher is the water repellence,
as depicted in Fig. 2a-e. A fabric is characterized
by a good water repellence if its ISO index, measured according to the normative,
is greater than 4. The fabrics have been set in environment at temperature 20±2°C
and with a 65±1% RH moisture. The results of the water repellence test,
performed to the 7 test fabrics in three replications, are showed in Table
4. The fireproof of the 7 test fabrics was assessed according to the standard
C.F.R. PART 1610 (Wu and Yang, 2008) that provides methods
of testing the flammability of clothing and textiles intended to be used for
clothing establishes three classes of flammability, sets forth the requirements
which textiles shall meet to be so classified and warns against the use of those
textiles which have burning characteristics unsuitable for clothing. More in
detail the normative provides the following three classes:
||Class 1 (Normal flammability): This class includes
textiles without nap, pile, tufting, flock, or other type of raised-fiber
surface, when the time of flame spread is 4 sec or more. Also a textile
napped, pile, tufted, flocked, or other having a raised-fiber surface is
defined in class 1 when the time of flame spread is more than 7 sec, or
when they burn with a rapid surface flash (from 0 to 7 sec), provided the
intensity of the flame is so low as not to ignite or fuse the base fabric
||Class 2 (Intermediate flammability): This class includes textiles
napped, pile, tufted, flocked, or other textiles having a raised-fiber surface
with a time of flame spread from 4 to 7 sec, both inclusive and the base
fabric ignites or fuses
||Class 3 (Rapid and intense burning): This class includes textiles
dangerously flammable and recognized by the trade as being unsuitable for
clothing because of their rapid and intense burning. In case of textiles
free from nap, pile, tufting, flock, or other type of raised-fiber surface
the time of flame spread is less than 4 sec. In case of napped, pile, tufted,
flocked, or other textiles having a raised-fiber surface the time of flame
spread is less than 4 sec and the intensity of flame is such as to ignite
or fuse the base fabric
||Visual description of the 5 ISO indexes (ISO 1, ISO 2,...,
ISO 5) for assessing the spray test. The higher is the value of the ISO
index and the higher is the water repellence (a) ISO 5 (100), (b) ISO 4
(90), (c) ISO 3 (80), (d) ISO 2 (70) and (e) ISO 1 (50)
|| Results of the water repellence test, performed to the 7
test fabrics in three replications and under different temperature
The fabrics are tested in two different conditions: as received and after refurbishing.
For each of the 7 test fabrics a number of 5 specimens is tested according to
the normative (the time of flame spread of the textile is taken as an average
time for 5 specimens). The refurbishing process comprises a washing (at 50°C)
a dry cleaning at 66°C and a cooling at environment temperature. The flammability
tester consists of a draft-proof ventilated chamber enclosing a standardized
ignition medium, sample rack and automatic timing device. The test shows that
all the fabrics have been classified into Class 1 before and after refurbishing.
||A picture of 7 specimens of fabrics obtained with the new
method. (a) R, (b) S , (c) T, (d) RIF X, (e) RIF X, (f) RIF Y and (g) RIF
The results of the test performed for the 7 test fabrics may be summarized
as follows. Figure 1, it may be noticed that fabrics identified
by the code S, Rif. X and Rif. Z are the only one respecting the shrinkage and
shortening values required by the Clotech definition (Seyam,
2000). In other words, among the 7 kind of fabrics developed during the
project, only three of them respects the definition of technical textiles. Anyway
this result may be considered a good advance in the field because of the use,
as already stated, of regenerated wool as a substitute of artificial fibers.
Moreover, with regard to the water repellent characteristics, these three innovative
and experimental fabrics have been classified into class ISO 4. Finally, all
the fabrics have been classified into Class 1 in terms of flammability. According
to these results the fabrics S, Rif. X and Rif. Z may be classified as Clotech.
Furthermore, all the devised fabrics have shown a good water repellence. This
is an important task because the objective of the work was to obtain a technical
textile with good water repellence but not to obtain a totally waterproof cloth
(Yanez et al., 2006). Reassuming, the tested
fabrics shows good aesthetic properties being based on the use of regenerated
wool instead of inorganic fibers. In Fig. 3a-g
a specimen of each of the 7 test fabrics is showed. The aesthetic properties
of these fabrics have been evaluated by the companies customers.
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