There are many compelling reasons for the recycling of waste from textile products and processes. They include conservation of resources, reduction of the need for landfills and paying the associated tipping fees, and provision of low-cost raw materials for products. Yet, in reality, the rate of recycling in textiles is not very high. Besides the often attributed reason of insufficient public willingness to participate in recycling, economics is often the reason behind the adoption of other modes of waste disposal. Although legislation could easily tip the balance in favor of recycling, such a forced move could have just the opposite effect in terms of environmental protection. Recycling, a seemingly obvious choice is more complicated than it appears.
Top ten reasons to stop Textile waste and Recycle Textiles
The Environmental Protection Agency estimates that about 97% of post-consumer textile waste is recyclable.
By simply donating all of your used textiles to participating thrift stores, you can help to significantly reduce the burden on our landfills.
Over 70% of the world's population uses secondhand clothes, so your old clothes can be used to help people in need.
By recycling textiles you benefit your local community by creating local jobs that generate local tax revenue.
Textile recycling companies, such as ours, work closely with charitable institutions to find new homes and uses for old clothing and fabric items, thus reducing the operating costs for thrift stores and freeing up funding to house, feed, and train the less fortunate.
Textile recycling requires less energy than any other type of recycling.
Textile recycling does not create any new hazardous waste or harmful by- products.
Un-wearable textiles can be reused as rags by paint stores, machine shops, auto shops, government, business and industry.
Un-wearable textiles can be converted for industrial uses such as noise reduction or upholstery.
Reclaimed fibres as raw materials
‘Reclaimed fibres’ are from a secondary cycle of processing. To obtain them, fabric-type or thread-type textile waste is mechanically broken down as far as the fibres. Conventionally, the waste is pre- treated by means of cutting or picking and then transported through a take-in unit, acting as a clamp, of a drum rotating at high speed. The textile structure is broken down by steel pins which are on the drum
surface, together with the clamping effect mentioned above. Structures will take several passages through the drum to become single fibres. Currently, raw materials available from reclaimed fibres have short fibre lengths but it is hard to clearly define their other characteristics. We should aim to break down the waste in question so as to achieve a type of reclaimed fibre which, with regard to its further application, is easy to characterize. In particular, we should aim to preserve fibre length as much as possible for most final applications.
Characteristics of reclaimed fibres
Reclaimed fibres are well suited to making non-woven and yarns. As compared with primary fibres, reclaimed fibres show different characteristics. The damage they suffer during production entails a wide spectrum of fibre lengths with a high share in short fibres as well as threads and pieces of fabric not broken up. Characteristics are influenced by the waste in question, its pre-treatment and the breaking-down process as such. In most cases, reclaimed fibres are available as blends. Examples are rare where the kinds of
polymers contained in them are easy to define. Generally, the values known concern the predominant polymer1 in the blend. As with the processing of reclaimed fibres into yarns, non-woven require proportions of broken-down
fibres to be as high as possible. Their lengths should be sufficient to undergo the spinning or web formation process in question. Pieces of yarn or thread still contained in the blend of reclaimed fibres directly contribute to matrix formation in the non-woven or they are further broken down into fibres during the carding process. Both short fibres and dusts, as well as remains of fabric, will
disturb the production process. Only an optimum breaking-down process with regard to the material will keep their proportions at a minimum. Present-day technologies allow between 25% and 55% of fibres of 10 mm length and longer. This does not concern easily broken-down textile structures such as low-torque yarns and non-woven which is low-grade or medium-grade reinforced. Reclaimed fibres are marketed at low price, primary fibre materials made of natural or synthetic substances, contributing to keeping prices down.
As compared with primary fibre materials, the quality of reclaimed fibres is hard to define. The measuring processes and equipment conventionally used are not very helpful here. This is due to the blends of reclaimed fibres being inhomogeneous and rich in short fibres and in textile remains which are not fibre-type (bits, pieces of thread and fabric). Test requirements differ from those used for primary fibres and testing will entail higher cost. Taking into consideration the range of applications known today, the parameters of highest interest are the degree of material break-down and fibre length, and the distribution of fibre lengths.
Products and markets
Reclaimed fibres can be manufactured from a variety of textile waste. Both quality and process ability of such fibres depend on the kind of waste. Well-known are the pure sorted fibres of high-quality which are achieved from spinning-fibre waste. In contrast,
reclaimed fibres made from end-of-life textiles are of much poorer quality. They will rarely be found of homogeneous fibre type.
There are many ways open to using reclaimed fibres in both textile and non-textile products. The suitability of processes depends on waste characteristics and on how much they cost.
Yarns are a frequent example of how reclaimed fibres can be used. Recycled wool has been re-used in industrial processes for a long time. Except for the conventional processes of carded yarn spinning and mixed shoddy spinning, there are up-to-date technologies tailored to utilize reclaimed fibres such as the rotor spinning process, the yarn covering process, and the friction spinning
process DREF, which allow economical production. Yarns made from reclaimed fibres may serve to produce fabrics for garments and household textiles as well as for simple technical applications. However, as yarns made from reclaimed fibres, in most cases, are grey or dark by nature, they are not frequently used in garments or household textiles. With technical yarns, colour ranks in second place. Even special-purpose fibre materials are made into reclaimed fibres today. Yarns designed for technical applications are, first of all, expected to meet clearly defined technical parameters. With wrap yarns, the following characteristics are most advantageous:
High strength (comparable with ring-spun yarns and threads),
Good roughness,
Higher voluminosity than rotor-spun or ring-spun yarns,
Good process ability due to low hairiness,
Good capacity to serve as in-depth filters, which is due to fibres, to a large degree, laying parallel to one another.
To achieve easy process ability, reclaimed fibres are frequently blended with primary fibres (about 15%).
Technical textiles as a market for products made from reclaimed fibres In highly industrialized countries, technical textiles are a growth market. It can be prognosticated that production of waste will also grow, so logically the interest in re- using this waste will also grow. The call for materials of primary fibres will continue to become ever louder and, at the same time, there will be cases where low-cost secondary fibres are suitable to replace them, if functionality stays equally good. In addition, it is obvious that reclaimed fibres serve best to develop a number of products whose production, due to the much higher cost, excludes the use of primary fibres
Reclaimed fibres to make technical textiles
It is most important to have reclaimed fibres available which are of the right quality with regard to the purpose and which are cheaper than primary fibres. Quality is expected, throughout the whole production period, to constantly remain within the parameters defined. Such parameters can, and should, be documented.
As for prices, primary and reclaimed fibres will more and more equalize due
to increasing costs for reprocessing waste. This concerns conventional kinds of fibre materials. To achieve a noticeable difference in price, the production of reclaimed fibres needs to become more economical. Processes continuing to depend on the waste in question need to become more efficient. At the same time, equipment should be up-to- date. Waste of high-grade and highly functional fibre materials are, of course, to be preferred. Such fibres being expensive, more space is automatically allowed so that the cost of recycling can be defined. With them, even more expensive recycling will remain economical.
Producers of reclaimed fibres being suppliers of raw materials, they should provide a range of, say, ten to thirty types of reclaimed fibre. With each of these, they should
clearly define parameters with regard to their possible uses and the products they may serve, such as
Kind of fibre material, blend of fibre material, colour of fibre, blend of shades,
Fibre lengths,
Fibre fineness, fibre strengths.
This requires that the producers should see to
Waste pre-treatment,
The variation of process parameters while breaking down the waste,
After-treatment,
Quality assurance.
They can deal with these requirements as follows:
Material pre-treatment (starts in the enterprises collecting the waste):
Is the waste washed or cleaned from dust?
Is the waste separated from non-textile components?
Is the waste sorted with respect to colour and polymers contained in it?
Is the waste pre-cut or pre-broken?
Pre-treatment goes on in the enterprises breaking the waste down as follows:
The waste should be blended with regard to the final products wanted and in order to enhance medium fibre length.
The waste fabric should be pre-broken.
Auxiliaries should be used to achieve easier breaking down (reducing the friction between the fibres – which will inspire customers to buy).
The waste should be pre-cut so as to achieve material sizes which allow best possible quality parameters and lowest-possible energy consumption.
Variation of process parameters while breaking down the waste
Comprehensive experiments have shown how process parameters influence both productivity and quality. Given the technical prerequisites to control process parameters (velocity of material transport, velocity of drum circumference) and taking into consideration the kind of waste, good-quality reclaimed fibres can be produced. Energy consumption can be held down at the lowest possible level. If producers define the interrelationship between the kind of material, equipment parameters, the quality of reclaimed fibre required, and energy consumption, they can develop waste-related and tailor-made processes.
After-treatment
After-treatment should focus on the further enhancement of the quality parameters reached in the breaking-down process, so that the reclaimed fibres become more competitive. The steps to be taken include
Cleaning from dust,
Blending (primary fibres in accordance with the application wanted), eliminating short fibres.
Bearing in mind costs, such steps will open up ways to product-related and tailor-made material qualities that may help producers market their products and yield best possible revenues. In addition, they will contribute to enhancing reclaimed fibre image. Seen with the user’s eyes, improved quality of reclaimed fibres means
Lower cost with regard to material pre-treatment,
Higher efficiency of the production technology (e.g. lower cleaning efforts),
Better process ability (less idle time due to material parameters).
Above all this, novel fields of application will be opened up, such as in the production of yarns, filter wovens, filter non-woven, and geo-textiles.
At the point of the producer of reclaimed fibres handing the materials over to the user, it is helpful to have a system of quality assessment available that allows the documentation of the technological parameters of the material. It will create the base on which contracts can be negotiated and questions of warranty clarified between the producer and the user. Such a system should help to define the parameters below within a short time and at low-cost:
Fibre length,
Degree of breaking down,
Polymers contained,
Proportion of dust, impurities etc.
Non-wovens made from reclaimed fibres Depending on product functions, reclaimed fibres can be looked upon as conventional in technical textiles, particularly in non-woven (mobility textiles which mainly serve to cover up surfaces or to insulate materials,
agro-textiles, and geo-textiles which are used to protect soil against erosion). In all these cases, reclaimed fibres are used because of low prices, or because they merely cover something up. However,
reclaimed fibres are also applied in non-woven to utilize highly valuable functional components. This concerns fibres which would not be available at a competitive price if made from primary materials, such as
The high-grade woollen hair found in laminated non-woven used to make upholstery composites for motor vehicle seats
Aramide fibres used to protect against cutting or impact penetration
Micro-fibre materials used for insulation or cleaning.
Yet there will remain a large field of applications where, due to the functionality expected, only primary fibres can be used both to make threads and fabrics.The following example illustrates this.
Many needle-punched geo-textiles will show a minimum strength resulting from the way they are made. They are used for simple separation purposes. However, their hydraulic performance with regard to water transportation in the non-woven direction and/or vertically to this direction is most important. This essential function is mainly influenced by the cavity structure in the non-woven. Hollow spaces in the non-woven are characterized by the size and the number of the pores contained in it, so logically they are interrelated with the fibre diameter or the fibre fineness.
Geo-textiles may be looked upon as an ideal field for the application of reclaimed fibres. To make them, it is important to use well- selected textile waste and to exactly tune the process parameters when breaking it up. In this way the quality requirements below can be met:
Type of fibre material: 100% polyester
Fibre fineness: 4.5 - 0.4 dtex
Average fibre length: at least 20 mm
Standards vary from country to country. European Standard EN 13249, for instance, prohibits the use of reclaimed fibres from end-of-life textile waste. Otherwise, reclaimed fibres of industrial waste need to meet the strengths required by the purpose or else must not be used. The table shows further fields of application of reclaimed fibres in technical textiles.
As can be seen in, both the aerodynamic and mechanical processes of web formation raise different questions with regard to the quality of reclaimed fibres. When producing the fibres, quality parameters can be set to some degree. Needle-punched warp-knitted
non-woven material serves us as a further example of how important the quality of reclaimed fibres is. This material is used to substitute for the components of polyurethane foam in laminated composites. The purely textile composite resulting allows one to recycle both the production waste generated and the composite structure itself at the end of its life. To make sure a non-woven containing 40% of reclaimed fibres can be well processed on a warp-knitting machine and shows full functionality when used as a laminated composite for a motor vehicle seat, the reclaimed fibre used needs to meet the following requirements:
A minimum of 80% wool contained in it,
A maximum of 35% of short fibres below 10 mm contained in it,
An average fibre length of at least 16 mm.
This is why an enterprise breaking the waste down faces a great challenge with regard to waste selection, the breaking-up process, fibre testing, and quality assurance.
More examples can be seen in the processing of fibre materials that are hard to break up, such as polypropylene and polyethylene. Their fibre characteristics of non-rottability, high strength, and resistance to chemicals make them highly suitable to be re-used in geo- textiles, needle felting (flooring material) or to make textile backs in same-polymer carpet structures. However, the thermal behavior of these fibre materials causes some trouble during pre-treatment. Process heat generated when mechanical energy is applied will easily reach softening or melting values. As a consequence, both polypropylene and polyethylene will suffer damage in blends with other fibre materials. This is why the
process needs to be further looked at. By applying a particular liquid cooling medium during the production process, the heat is eliminated to such a degree that, at the end of the breaking-up process, dry fibres are available right away. In this process, the equipment is exposed to corrosion; however, it is felt that this can be neglected as long as high-value fibre materials are reclaimed.
In this respect, both producers and users do not face any limits. It does not matter whether reclaimed fibres are used to recycle waste or to lower costs or market products with improved characteristics. There is only one way to go:
Define the fibre profile with regard to quality, price, quantity,
Make sure the waste in question is continuously available,
Design the breaking-down process as related to the waste in question and the fibre parameters required,
Ensure the parameters of fibre quality can be clearly defined,
Check the complex of requirements with regard to the reclaimed fibre and production start-up.
Textiles for use in motor vehicles
Not every kind of textile production waste is suitable to undergo the conventional way of recycling by breaking down the structure in question. In addition to elastic textile structures and high-strength fibre materials, there are non-woven sandwich type structures which need to be considered here. For these reasons we looked into the production waste found in the automotive industry. It is hard to
recycle, which is often due to needle-punched non-woven being bonded by means of chemical agents. In other cases, the trouble arises from several components being laminated. In addition, there are a high proportion of thermoplastic fibre materials so consequently, when heat is applied to mould parts, the textile matrix of non-thermoplastic fibres is converted into an interlocking composite that is hard to break up.
However, our research so far has shown that it is possible to break up hard moulded textile waste to achieve reclaimed fibres. To this end, it is important to tailor processes. We made tests at sub-industrial levels on three breaking-down plants in different enterprises. It emerged that the key to success is a process of rough breaking up by means of picking and a rough-breaking passage. In addition, the blending-in of 20% to 30% ‘conventional’ textile waste ensures good process continuity.
After-treatment is definitely necessary; this concerns the careful cleaning away of dust from the powdery bonding agents, and eliminating rough bits. We made an
Production of reclaimed fibres and their re-use in the motor vehicle
Industrial -scale test amounting to 10 tons and including the after-treatment described above. For this purpose, we collaborated with a recycling enterprise where all the necessary plants were available. After that, we tested the blend of reclaimed fibres we had made in another enterprise and found it takes particular technological steps to be successful. A fibre blend containing about 20% of the waste described above reaches its technological limits. Further research is necessary to improve, first of all, process effectively. Currently, material throughput is still too low and costly. In addition, we must focus on better waste pre-treatment so that we make a blend ready for use. Both producers of reclaimed fibres and users will benefit from progress in this respect as they will not need to pre-treat the material any further.
For one supplier of the automotive industry only, it can be estimated about ten tons of waste are generated per month. This makes it clear how the recycling processes we have developed may contribute to both process economy and a healthy environment. It is possible to make products of high interest and functionality, quality being sufficient and prices competitive. Their production may become low-cost. Ways are open into material cycles.
Conclusion
The development of novel products partly or totally made of reclaimed fibres will stay of great interest. What raises the call for recycled raw materials is the lack in good-value primary raw materials or their high price. In the long run, both quantities and prices of primary raw materials will shadow those of crude oil. Consequently, textile recycling will become ever more important. Bearing in mind the availability of fossil raw materials to make synthetic fibres is limited, it can be forecast that reclaimed fibres or fibres recycled to other processes will rise in importance. All these tendencies will inspire engineers to innovative economical recycling processes which, no doubt, will include the field of textiles.
References
Eisele D. (1996), ‘Reclaimed fibres. Characteristics. Background,’ Melliand Textilberichte, 77, 4, 199–202.
M�gel M., M�gel M., Bieber B. (1993), ‘First research results to define a number of selected textile-physical parameters of reclaimed fibres,’ Kolloquium Reissfaser ’93, S�chsisches Textilforschungsinstitut e.V. Chemnitz.
Fischer H., Rettig D., Harig H. (1999), ‘Image processing to measure the length distribution of reclaimed fibres,’ Melliand Textilberichte, 80, 358–360.
Bohnhoff A., Petershans J. (2001), ‘Sorting carpets non-centrally,’ 28th Aachen Textile Conference, Aachen, D 28–29 November, DWI Reports, 125 (2002), 242–252.
Anon. (2001), ‘Infinity and beyond. Carpet recycling,’ International Carpet Bulletin – (ICB) March, 8–10.
Gulich B. (2000), ‘Breaking textile structures up and web formation – trials to combine processes to make heavy-weight nonwovens of textile waste and reproducing raw materials,’ 15, Hofer Vliesstofftage Hof 08.–09.11.2000.
Gulich B., B�ttcher P. (1999), ‘Recycling needle-punched textile flooring material 38.’
Internationale Chemiefasertagung/20. Intercarpet Dornbirn/A 15.–17.09.1999.
Eisele D. (1992), ‘Recycled materials of reclaimed cotton and phenoplastic material – a well-proven system,’ Melliand Textilberichte, 73, 11, 873–878.
Radetic M. et al. (2003), ‘Application of recycled wool based nonwoven material for purification and cleaning of waters,’ 29th Aachen Textile Conference, Aachen D 27–28 Nov., DWI Reports 126, 274–283.
Elsasser N., Maetschke O., Wulfhorst B. (1999), ‘Reclaimed fibres in spinning processes,’ Melliand Textilberichte, 80, 361–365.
B�ttcher P. (2003), ‘Textile recycling in a world of raw materials being rare and of the law being strict,’ 6 STFI-Kolloquium Reissfaser, Chemnitz, D 1–2 December.
Tenckhoff E. (2002), ‘The call for energy – present-day and future,’ CIT, 7, 4–9.
The authors are associated with - Department of Fashion Technology, Angel College of Engineering & Technology, Tirupur.
Top ten reasons to stop Textile waste and Recycle Textiles
The Environmental Protection Agency estimates that about 97% of post-consumer textile waste is recyclable.
By simply donating all of your used textiles to participating thrift stores, you can help to significantly reduce the burden on our landfills.
Over 70% of the world's population uses secondhand clothes, so your old clothes can be used to help people in need.
By recycling textiles you benefit your local community by creating local jobs that generate local tax revenue.
Textile recycling companies, such as ours, work closely with charitable institutions to find new homes and uses for old clothing and fabric items, thus reducing the operating costs for thrift stores and freeing up funding to house, feed, and train the less fortunate.
Textile recycling requires less energy than any other type of recycling.
Textile recycling does not create any new hazardous waste or harmful by- products.
Un-wearable textiles can be reused as rags by paint stores, machine shops, auto shops, government, business and industry.
Un-wearable textiles can be converted for industrial uses such as noise reduction or upholstery.
Reclaimed fibres as raw materials
‘Reclaimed fibres’ are from a secondary cycle of processing. To obtain them, fabric-type or thread-type textile waste is mechanically broken down as far as the fibres. Conventionally, the waste is pre- treated by means of cutting or picking and then transported through a take-in unit, acting as a clamp, of a drum rotating at high speed. The textile structure is broken down by steel pins which are on the drum
surface, together with the clamping effect mentioned above. Structures will take several passages through the drum to become single fibres. Currently, raw materials available from reclaimed fibres have short fibre lengths but it is hard to clearly define their other characteristics. We should aim to break down the waste in question so as to achieve a type of reclaimed fibre which, with regard to its further application, is easy to characterize. In particular, we should aim to preserve fibre length as much as possible for most final applications.
Characteristics of reclaimed fibres
Reclaimed fibres are well suited to making non-woven and yarns. As compared with primary fibres, reclaimed fibres show different characteristics. The damage they suffer during production entails a wide spectrum of fibre lengths with a high share in short fibres as well as threads and pieces of fabric not broken up. Characteristics are influenced by the waste in question, its pre-treatment and the breaking-down process as such. In most cases, reclaimed fibres are available as blends. Examples are rare where the kinds of
polymers contained in them are easy to define. Generally, the values known concern the predominant polymer1 in the blend. As with the processing of reclaimed fibres into yarns, non-woven require proportions of broken-down
fibres to be as high as possible. Their lengths should be sufficient to undergo the spinning or web formation process in question. Pieces of yarn or thread still contained in the blend of reclaimed fibres directly contribute to matrix formation in the non-woven or they are further broken down into fibres during the carding process. Both short fibres and dusts, as well as remains of fabric, will
disturb the production process. Only an optimum breaking-down process with regard to the material will keep their proportions at a minimum. Present-day technologies allow between 25% and 55% of fibres of 10 mm length and longer. This does not concern easily broken-down textile structures such as low-torque yarns and non-woven which is low-grade or medium-grade reinforced. Reclaimed fibres are marketed at low price, primary fibre materials made of natural or synthetic substances, contributing to keeping prices down.
As compared with primary fibre materials, the quality of reclaimed fibres is hard to define. The measuring processes and equipment conventionally used are not very helpful here. This is due to the blends of reclaimed fibres being inhomogeneous and rich in short fibres and in textile remains which are not fibre-type (bits, pieces of thread and fabric). Test requirements differ from those used for primary fibres and testing will entail higher cost. Taking into consideration the range of applications known today, the parameters of highest interest are the degree of material break-down and fibre length, and the distribution of fibre lengths.
Products and markets
Reclaimed fibres can be manufactured from a variety of textile waste. Both quality and process ability of such fibres depend on the kind of waste. Well-known are the pure sorted fibres of high-quality which are achieved from spinning-fibre waste. In contrast,
reclaimed fibres made from end-of-life textiles are of much poorer quality. They will rarely be found of homogeneous fibre type.
There are many ways open to using reclaimed fibres in both textile and non-textile products. The suitability of processes depends on waste characteristics and on how much they cost.
Yarns are a frequent example of how reclaimed fibres can be used. Recycled wool has been re-used in industrial processes for a long time. Except for the conventional processes of carded yarn spinning and mixed shoddy spinning, there are up-to-date technologies tailored to utilize reclaimed fibres such as the rotor spinning process, the yarn covering process, and the friction spinning
process DREF, which allow economical production. Yarns made from reclaimed fibres may serve to produce fabrics for garments and household textiles as well as for simple technical applications. However, as yarns made from reclaimed fibres, in most cases, are grey or dark by nature, they are not frequently used in garments or household textiles. With technical yarns, colour ranks in second place. Even special-purpose fibre materials are made into reclaimed fibres today. Yarns designed for technical applications are, first of all, expected to meet clearly defined technical parameters. With wrap yarns, the following characteristics are most advantageous:
High strength (comparable with ring-spun yarns and threads),
Good roughness,
Higher voluminosity than rotor-spun or ring-spun yarns,
Good process ability due to low hairiness,
Good capacity to serve as in-depth filters, which is due to fibres, to a large degree, laying parallel to one another.
To achieve easy process ability, reclaimed fibres are frequently blended with primary fibres (about 15%).
Technical textiles as a market for products made from reclaimed fibres In highly industrialized countries, technical textiles are a growth market. It can be prognosticated that production of waste will also grow, so logically the interest in re- using this waste will also grow. The call for materials of primary fibres will continue to become ever louder and, at the same time, there will be cases where low-cost secondary fibres are suitable to replace them, if functionality stays equally good. In addition, it is obvious that reclaimed fibres serve best to develop a number of products whose production, due to the much higher cost, excludes the use of primary fibres
Reclaimed fibres to make technical textiles
It is most important to have reclaimed fibres available which are of the right quality with regard to the purpose and which are cheaper than primary fibres. Quality is expected, throughout the whole production period, to constantly remain within the parameters defined. Such parameters can, and should, be documented.
As for prices, primary and reclaimed fibres will more and more equalize due
to increasing costs for reprocessing waste. This concerns conventional kinds of fibre materials. To achieve a noticeable difference in price, the production of reclaimed fibres needs to become more economical. Processes continuing to depend on the waste in question need to become more efficient. At the same time, equipment should be up-to- date. Waste of high-grade and highly functional fibre materials are, of course, to be preferred. Such fibres being expensive, more space is automatically allowed so that the cost of recycling can be defined. With them, even more expensive recycling will remain economical.
Producers of reclaimed fibres being suppliers of raw materials, they should provide a range of, say, ten to thirty types of reclaimed fibre. With each of these, they should
clearly define parameters with regard to their possible uses and the products they may serve, such as
Kind of fibre material, blend of fibre material, colour of fibre, blend of shades,
Fibre lengths,
Fibre fineness, fibre strengths.
This requires that the producers should see to
Waste pre-treatment,
The variation of process parameters while breaking down the waste,
After-treatment,
Quality assurance.
They can deal with these requirements as follows:
Material pre-treatment (starts in the enterprises collecting the waste):
Is the waste washed or cleaned from dust?
Is the waste separated from non-textile components?
Is the waste sorted with respect to colour and polymers contained in it?
Is the waste pre-cut or pre-broken?
Pre-treatment goes on in the enterprises breaking the waste down as follows:
The waste should be blended with regard to the final products wanted and in order to enhance medium fibre length.
The waste fabric should be pre-broken.
Auxiliaries should be used to achieve easier breaking down (reducing the friction between the fibres – which will inspire customers to buy).
The waste should be pre-cut so as to achieve material sizes which allow best possible quality parameters and lowest-possible energy consumption.
Variation of process parameters while breaking down the waste
Comprehensive experiments have shown how process parameters influence both productivity and quality. Given the technical prerequisites to control process parameters (velocity of material transport, velocity of drum circumference) and taking into consideration the kind of waste, good-quality reclaimed fibres can be produced. Energy consumption can be held down at the lowest possible level. If producers define the interrelationship between the kind of material, equipment parameters, the quality of reclaimed fibre required, and energy consumption, they can develop waste-related and tailor-made processes.
After-treatment
After-treatment should focus on the further enhancement of the quality parameters reached in the breaking-down process, so that the reclaimed fibres become more competitive. The steps to be taken include
Cleaning from dust,
Blending (primary fibres in accordance with the application wanted), eliminating short fibres.
Bearing in mind costs, such steps will open up ways to product-related and tailor-made material qualities that may help producers market their products and yield best possible revenues. In addition, they will contribute to enhancing reclaimed fibre image. Seen with the user’s eyes, improved quality of reclaimed fibres means
Lower cost with regard to material pre-treatment,
Higher efficiency of the production technology (e.g. lower cleaning efforts),
Better process ability (less idle time due to material parameters).
Above all this, novel fields of application will be opened up, such as in the production of yarns, filter wovens, filter non-woven, and geo-textiles.
At the point of the producer of reclaimed fibres handing the materials over to the user, it is helpful to have a system of quality assessment available that allows the documentation of the technological parameters of the material. It will create the base on which contracts can be negotiated and questions of warranty clarified between the producer and the user. Such a system should help to define the parameters below within a short time and at low-cost:
Fibre length,
Degree of breaking down,
Polymers contained,
Proportion of dust, impurities etc.
Non-wovens made from reclaimed fibres Depending on product functions, reclaimed fibres can be looked upon as conventional in technical textiles, particularly in non-woven (mobility textiles which mainly serve to cover up surfaces or to insulate materials,
agro-textiles, and geo-textiles which are used to protect soil against erosion). In all these cases, reclaimed fibres are used because of low prices, or because they merely cover something up. However,
reclaimed fibres are also applied in non-woven to utilize highly valuable functional components. This concerns fibres which would not be available at a competitive price if made from primary materials, such as
The high-grade woollen hair found in laminated non-woven used to make upholstery composites for motor vehicle seats
Aramide fibres used to protect against cutting or impact penetration
Micro-fibre materials used for insulation or cleaning.
Yet there will remain a large field of applications where, due to the functionality expected, only primary fibres can be used both to make threads and fabrics.The following example illustrates this.
Many needle-punched geo-textiles will show a minimum strength resulting from the way they are made. They are used for simple separation purposes. However, their hydraulic performance with regard to water transportation in the non-woven direction and/or vertically to this direction is most important. This essential function is mainly influenced by the cavity structure in the non-woven. Hollow spaces in the non-woven are characterized by the size and the number of the pores contained in it, so logically they are interrelated with the fibre diameter or the fibre fineness.
Geo-textiles may be looked upon as an ideal field for the application of reclaimed fibres. To make them, it is important to use well- selected textile waste and to exactly tune the process parameters when breaking it up. In this way the quality requirements below can be met:
Type of fibre material: 100% polyester
Fibre fineness: 4.5 - 0.4 dtex
Average fibre length: at least 20 mm
Standards vary from country to country. European Standard EN 13249, for instance, prohibits the use of reclaimed fibres from end-of-life textile waste. Otherwise, reclaimed fibres of industrial waste need to meet the strengths required by the purpose or else must not be used. The table shows further fields of application of reclaimed fibres in technical textiles.
As can be seen in, both the aerodynamic and mechanical processes of web formation raise different questions with regard to the quality of reclaimed fibres. When producing the fibres, quality parameters can be set to some degree. Needle-punched warp-knitted
non-woven material serves us as a further example of how important the quality of reclaimed fibres is. This material is used to substitute for the components of polyurethane foam in laminated composites. The purely textile composite resulting allows one to recycle both the production waste generated and the composite structure itself at the end of its life. To make sure a non-woven containing 40% of reclaimed fibres can be well processed on a warp-knitting machine and shows full functionality when used as a laminated composite for a motor vehicle seat, the reclaimed fibre used needs to meet the following requirements:
A minimum of 80% wool contained in it,
A maximum of 35% of short fibres below 10 mm contained in it,
An average fibre length of at least 16 mm.
This is why an enterprise breaking the waste down faces a great challenge with regard to waste selection, the breaking-up process, fibre testing, and quality assurance.
More examples can be seen in the processing of fibre materials that are hard to break up, such as polypropylene and polyethylene. Their fibre characteristics of non-rottability, high strength, and resistance to chemicals make them highly suitable to be re-used in geo- textiles, needle felting (flooring material) or to make textile backs in same-polymer carpet structures. However, the thermal behavior of these fibre materials causes some trouble during pre-treatment. Process heat generated when mechanical energy is applied will easily reach softening or melting values. As a consequence, both polypropylene and polyethylene will suffer damage in blends with other fibre materials. This is why the
process needs to be further looked at. By applying a particular liquid cooling medium during the production process, the heat is eliminated to such a degree that, at the end of the breaking-up process, dry fibres are available right away. In this process, the equipment is exposed to corrosion; however, it is felt that this can be neglected as long as high-value fibre materials are reclaimed.
In this respect, both producers and users do not face any limits. It does not matter whether reclaimed fibres are used to recycle waste or to lower costs or market products with improved characteristics. There is only one way to go:
Define the fibre profile with regard to quality, price, quantity,
Make sure the waste in question is continuously available,
Design the breaking-down process as related to the waste in question and the fibre parameters required,
Ensure the parameters of fibre quality can be clearly defined,
Check the complex of requirements with regard to the reclaimed fibre and production start-up.
Textiles for use in motor vehicles
Not every kind of textile production waste is suitable to undergo the conventional way of recycling by breaking down the structure in question. In addition to elastic textile structures and high-strength fibre materials, there are non-woven sandwich type structures which need to be considered here. For these reasons we looked into the production waste found in the automotive industry. It is hard to
recycle, which is often due to needle-punched non-woven being bonded by means of chemical agents. In other cases, the trouble arises from several components being laminated. In addition, there are a high proportion of thermoplastic fibre materials so consequently, when heat is applied to mould parts, the textile matrix of non-thermoplastic fibres is converted into an interlocking composite that is hard to break up.
However, our research so far has shown that it is possible to break up hard moulded textile waste to achieve reclaimed fibres. To this end, it is important to tailor processes. We made tests at sub-industrial levels on three breaking-down plants in different enterprises. It emerged that the key to success is a process of rough breaking up by means of picking and a rough-breaking passage. In addition, the blending-in of 20% to 30% ‘conventional’ textile waste ensures good process continuity.
After-treatment is definitely necessary; this concerns the careful cleaning away of dust from the powdery bonding agents, and eliminating rough bits. We made an
Production of reclaimed fibres and their re-use in the motor vehicle
Industrial -scale test amounting to 10 tons and including the after-treatment described above. For this purpose, we collaborated with a recycling enterprise where all the necessary plants were available. After that, we tested the blend of reclaimed fibres we had made in another enterprise and found it takes particular technological steps to be successful. A fibre blend containing about 20% of the waste described above reaches its technological limits. Further research is necessary to improve, first of all, process effectively. Currently, material throughput is still too low and costly. In addition, we must focus on better waste pre-treatment so that we make a blend ready for use. Both producers of reclaimed fibres and users will benefit from progress in this respect as they will not need to pre-treat the material any further.
For one supplier of the automotive industry only, it can be estimated about ten tons of waste are generated per month. This makes it clear how the recycling processes we have developed may contribute to both process economy and a healthy environment. It is possible to make products of high interest and functionality, quality being sufficient and prices competitive. Their production may become low-cost. Ways are open into material cycles.
Conclusion
The development of novel products partly or totally made of reclaimed fibres will stay of great interest. What raises the call for recycled raw materials is the lack in good-value primary raw materials or their high price. In the long run, both quantities and prices of primary raw materials will shadow those of crude oil. Consequently, textile recycling will become ever more important. Bearing in mind the availability of fossil raw materials to make synthetic fibres is limited, it can be forecast that reclaimed fibres or fibres recycled to other processes will rise in importance. All these tendencies will inspire engineers to innovative economical recycling processes which, no doubt, will include the field of textiles.
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The authors are associated with - Department of Fashion Technology, Angel College of Engineering & Technology, Tirupur.
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