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11.06.2025

ITA Institut für Textiltechnik der RWTH Aachen University

PE-based, spun-dyed and sustainable clothing made from organic raw materials

Fibres Yarns Knittings Recycling Sustainability Fashion

Abstract

The bioPEtex project in the BIOTEXFUTURE Innovation Space aims to develop sustainable clothing made from bio-based raw materials in the form of spun-dyed T-shirts. In an industry heavily dominated by fossil-based polymers such as polyester, bio-based polyethylene (bioPE), a bio-based polymer made from fermented starches or sugars, offers an environmentally friendly alternative. BioPE has the same properties as fossil-based PE and is fully recyclable. The use of spun-dyed bioPE also reduces energy and water consumption by 50 % and CO2 emissions by 60 %. The project involves the development of sustainably dyed compounds from bioPE for the spun-dyeing process and the development of multifilament yarns through melt spinning and false-twist texturing. The yarns are knitted on seamless machines and a T-shirt demonstrator is manufactured, which is finished with a sustainable elastic finish. The results will not only reduce the ecological footprint of the textile industry, but also promote innovative approaches to the circular economy.

Report

Introduction

The global annual man-made fibre production is growing steadily and is expected to exceed 100 million tonnes by 2030. Polyethylene terephthalate (PET) from the polyester (PES) family is the most widely used polymer, with an 80 % market share. Global clothing production alone almost doubled between 2000 and 2015. More than 80 % of all fibres produced are now used for clothing. Between 30 and 60 % of PET produced worldwide is used in clothing, i.e. approx. 18 to 36 million tonnes. This makes PET the most widely used material for clothing (as of 2021). The textile industry therefore faces enormous ecological challenges, particularly due to the high proportion of fossil raw materials used in textile production. Fossil-based polyesters account for around 52 % of the market and have a significant negative impact on the environment and resource consumption. Synthetic fibres in clothing are largely made from these fossil-based polyesters, the main component of which is PET, which is not yet 100 % bio-based. Clothing made from 100 % biopolymers has so far only been shown in studies and flagship projects, as it is too expensive for the mass market and not available in sufficient quantities. The bioPEtex project aims to establish 100 % bio-based polyethylene (bioPE) in the clothing market. The large-volume thermoplastic drop-in polymer is used to produce mono material, thermomechanically recyclable clothing. To achieve this, the challenge that PE is not produced for continuous fibre production and that there are no designated types for this purpose and no textile plant technology designed for the polymer must be solved. Based on preliminary work at the Institute für Textiltechnik (ITA), the current project status and Alberghini et al., it is foreseeable that the project will be successful. The consortium's expertise is ideally suited for rapid implementation. [Tex22; AHL+21; SB20Materials and Methods

In the scope of this project, commercially available bio-based polyethylenes are selected, procured and modified (see Figure 1).

Spinnable compounds made from BioPE are then developed. For subsequent spin dyeing in the melt spinning process, colour masterbatches with bio-based colour pigments are developed by our industry partner TECNARO GmbH, Ilsfeld, Germany, in order to realise a sustainable alternative to conventional dyeing with dyes. In addition, conventional dyeing of PE is challenging [BBO+13]. Various textured multifilament yarns with up to 100 filaments are developed from these bioPE compounds using melt spinning and texturing processes on a semi-industrial scale, so that a bio-based T-shirt can be manufactured. Until now, PE has only been used in the industry for staple fibres, highly drawn fibres for technical applications or for carbon fibres – but not yet as yarn in clothing [Fou99; Pei18; Wor17]. In addition to the elasticity provided by the meshes in the knitted fabric, innovative, pre-competitive, sustainable textile finishes are being tested and further developed.

Results

Initial results show promising progress in the processing of bioPE into spun-dyed yarns with suitable properties for textile applications. BioPE can be processed into multifilament yarns in stable melt spinning processes. Process development with dyed bioPE compounds is currently underway (see Figure 2).

The resulting partially oriented yarns (POY) with currently 96 filaments and a single filament titre of approx. 1 dtex have suitable properties for subsequent false-twist texturing (see Figure 3). Production speeds for melt spinning are currently in the industrial range (2,500 m/min). In a next step, yarns with 30 filaments and a higher single filament titre will be spun in order to give the resulting textile more stability in combination with the fine yarns.

Tensile strengths of approx. 20 cN/tex have been achieved to date, thus already meeting the target values derived from PET-POY. False-twist texturing on a laboratory scale (ITA) and on a semi-industrial scale (BB Engineering GmbH, Remscheid, Germany) has also been successful. The mechanical properties of the textured yarns (draw-textured yarn, DTY) are thus improved and the yarn volume and heat retention capacity are increased (see Figure 4). The close-up image of the DTY below shows that no tangling was introduced on a laboratory scale and that the yarn cohesion is therefore not yet ideal. However, the DTY can already be processed into a knitted fabric without any problems. These shortcomings are also remedied on a semi-industrial scale.

The resulting natural fibre-like, cool feel now makes it possible to use the yarn in textiles. Initial knitting trials with the lab-scale DTY have been successful at our industrial partner FALKE KGaA in Schmallenberg, Germany, once again confirming the cooling sensation when the textile is touched. Further yarns are being developed so that the next step can be to produce a T-shirt for sports applications using semi-industrial yarns and validate it as a demonstrator. The development of the bio-based elastic finish is also currently underway.

Summary

The bioPEtex project represents an innovative approach to producing sustainable clothing from bio-based materials. Targeted research and development aims to achieve both ecological and economic benefits. The results achieved could contribute to significantly reducing the ecological footprint of the textile industry and setting new standards for recyclability in the fashion industry. So far, developments with bio-based PE compounds have been successful, and smooth, partially oriented as well as textured yarns can be produced on a semi-industrial scale and processed into a cooling knit fabric. Validation as a demonstrator in the form of a seamless, bio-based T-shirt with elastic bio-based finishing is still pending in the further course of the project.

Acknowledgement

We thank the Federal Ministry of Research, Technology and Space for funding the Innovation Space BIOTEXFUTURE and the research project bioPEtex (031B1496). Furthermore, we would also like to thank everyone involved in this project for their contributions and commitment.

Bibliography

[AHL+21] Alberghini, M.; Hong, S.; Lozano, L. M.; Korolovych, V.; Huang, Y.; Signorato, F.; Zandavi, S. H.; Fucetola, C.; Uluturk, I.; Tolstorukov, M. Y.; Chen, G.; Asinari, P.; Osgood, R. M.; Fasano, M.; Boriskina, S. V.:
Sustainable polyethylene fabrics with engineered moisture transport for passive cooling
Nature Sustainability 4 (2021), H. 8, S. 715–724

[BBO+13] Baur, E.; Brinkmann, S.; Osswald, T. A.; Rudolph, N.; Schmachtenberg, E.; Saechtling, H.:
Saechtling Kunststoff Taschenbuch. 31. Ausgabe, [komplett überarb., aktualisiert und zum ersten Mal in Farbe]Aufl..- München: Hanser, 2013

[Fou99] Fourné, F.:
Synthetic Fibers. Hanser, München, 1999

[Pei18] Peijs, T.:
1.5 High Performance Polyethylene Fibers:
Comprehensive Composite Materials II: Elsevier, 2018, S. 86–126

[SB20] Siracusa, V.; Blanco, I.:
Bio-Polyethylene (Bio-PE), Bio-Polypropylene (Bio-PP) and Bio-Poly(ethylene terephthalate) (Bio-PET): Recent Developments in Bio-Based Polymers Analogous to Petroleum-Derived Ones for Packaging and Engineering Applications
Polymers 12 (2020), H. 8

[Tex22] Textile Exchange:
Preferred Fiber and Materials Market Report 2022
Burbank, California: 10/2022

[Wor17] Wortberg, G.:
Entwicklung polyethylenbasierter Precursoren für die thermochemische Stabilisierung zur Carbonfaserherstellung. Shaker Verlag, Dissertation,

 

Authors: M. Ortega J. Langer R. Morgenroth M. van Haren G. Mourgas A. Langer T. Gries

Contact:

ITA Institut für Textiltechnik der RWTH Aachen University, Otto-Blumenthal-Straße 1, 52074 Aachen, Germany

Clothtech SportTec Oekotech

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02.08.2023

ITA Institut für Textiltechnik der RWTH Aachen University

Strain sensing of textile structures with polymer-based bicomponent filaments

Fibres Sensor Technology Smart Textiles

Abstract

Strain monitoring can be critical for structures such as light weight composites or civil structures. Many of these application already use textiles or fibres, meaning that sensor fibres are predestined for incorporation and monitoring. Polymer-based sensor filaments allow for a wide range of tailorability for the individual applications. In this work, particle based nanocomposite filaments are melt spun. Afterward, they are characterised regarding the morphology and static resistivities. Lastly, selected filaments are tested regarding the dynamic resistivity to evaluate the suitability for use as a strain sensor using the example of carbon fibre composite structures. It is shown in this work that the sensor filament can be produced by the melt spinning process. Further challenges which are not yet solved included the identification of outlier filaments without destructive testing, as well as the data analysis for the generation of a calibration curve. In further work, other application cases will be tested as well as additional, elastic filaments.

Report

Introduction

Smart textiles and wearables are no new topics in the field of textile research. Nevertheless, they have yet to reach the market breakthrough expected. Instead, the drastic increase in the market share is pushed into the future with each new study. Despite this breakthrough delay, there is no shortage of work in the academic field.

Much of the work is currently focusing on employing metal coated yarns for applications in which electrical signals are detected and transmitted. Although the electrical conductivity of these materials is in the range of typical metals, they are often negatively influenced from external factors such as moisture and friction. One approach to combat the wear is to employ a material in which the conductive component is integrated during production rather than subsequently applied as a coating. This can be done through the melt compounding of conductive particles into thermoplastic polymers, which are then extruded to filaments. These materials are inherently conductive but, when spun alone, are still subject to the influence of external moisture.

In order to solve both problems of wear and influence of moisture, bicomponent thermoplastic filaments have been developed at ITA. Additionally, these filaments open up opportunities for new filament sensors to be integrated not only in clothing but also lightweight composites and civil structures. The production, characterisation and outlook of these novel filaments is described below.

Production

Melt spinning is a method for the continuous filament production. Specifically, monofilament melt spinning is used for the manufacturing of products such as fishing line, tennis strings and 3D-printer filament. With the addition of a second extruder bicomponent filaments can also be produced. A schematic visualisation of the employed bicomponent monofilament machine is shown in Figure 1.

In order to generate an inherently conductive compound, conductive nanoparticles are mixed with a carrier thermoplastic material. In this work, a commercially available compound consisting of 4 wt.% carbon nanotubes (CNTs) and 96 wt.% thermoplastic polyurethane (TPU) from the company NanoCyl SA, Sambreville, Belgium is used. This compound is the core component of the filament. Two different sheath components are used: Polypropylene (PP) Moplen HP561R, LyondellBasel Industries Holding B.V., Rotterdam, The Netherlands and TPU 1185 from BASF Polyurethane, Lemsförde, Germany. The resulting filaments will be further referred to as PP/TPU and TPU/TPU. The production parameters for the filaments are shown in Table 1.

Table 1:            Production parameters for the monofilaments (see attached pdf)

Results and discussion

The cross-sections of the filaments are analysed using light microscopy. The samples are first embedded in epoxy and polished. The images of the filaments are shown in Figure 2. The variance of the final areas and diameters stem from the difference in the material density in the molten and solid state. In both filaments a clear distinction between the core and sheath components is visible.

Electrical analysis to determine the static and dynamic electrical resistance is done by cutting the filament cleanly to expose the core and then dipping the filament in silver paint. An electrical path from the core to the surface of the filament is generated and the filament can be contacted with standard clamps. This method is schematically shown in Figure 3. Unfortunately, due to the softness of the TPU in the sheath, this method is not suitable for the electrical contacting of the TPU/TPU filament. Therefore, only the results of the PP/TPU filament are presented.

For the first quantitative tests, electrical resistance is measured simultaneously while applying a tensile strain. The starting length of the filament to be deformed is 5 cm and a constant speed of 1 mm/min is applied. This roughly corresponds to a strain rate of 2 %/min. This slow speed is derived from the strain rates for testing of geoplastics. The total length of the sensor filament, including the length clamped in the tensile machine and length needed to attach the multimeter, is 20 cm. Five filament samples are tested in this set-up. The test set-up is shown schematically in Figure 4.

In conventional strain gauge technology, the electrical response of the sensor is given as the normalised change of the resistance using the equation below. Here Rε is the resistance at strain ε and R0 is the resistance at strain 0 %.

 

ΔR/R [-] = Rε [Ω] - R0 [Ω]R0 [Ω]

(1)

This same convention is initially used for the analysis of the sensor filaments. The resulting curves for the filament PP/TPU is shown in Figure 5, left. It can be seen that, although the general trend of the curves is similar, an exact calibration of the sensors is not yet possible. One assumption for the varying trends results from the variance in the R0 of the filaments, causing a difference in the scaling of the curves as shown is Eq. 1. The initial values R0 can be seen in Figure 6.

The sensor response is then calculated in regards only to the change in resistance, as opposed to the normalised change. This alternate equation can be seen below and the resulting diagram can be seen in Figure 5, right.

 

ΔR [Ω] = R [Ω] -R0 [Ω]

(2)

 

It can be seen that the response of the five tested filaments is in much more agreement when only the change in the resistance is considered. This result demonstrates the fact that the analysis of the novel sensor filaments may not be taken completely from conventional, current solutions and may have to be rethought entirely. Additionally, there seems to be a correlation between the noise of the measurements and the high R0, for example for repetitions 4 and 5. When these filaments are removed from the visual representation, a calibration of the sensor filament can be done with high precision until 7 %, which is generally larger than expected strains in structural applications (Figure 7).

Conclusion and Outlook

The results presented here show the extreme potential of polymer-based sensor filaments. Through the production parameters, the filaments can be tailored to match specific requirements of a variety of applications. These sensor filaments can revolutionise structural health monitoring in civil structures, lightweight components and many, yet to be discovered, applications. In order to realise this technological breakthrough, work still needs to be done in various aspects:

  • Identification of more technical applications, for which the sensor filaments can be relevant
  • Mechanical and electrical contacting of the filaments in a more robust manner, as well as contacting of the softer TPU/TPU filaments
  • Variation of testing parameters in order to investigate the sensor response under different loading cases (cyclic, relaxation, creep, different strain rates, combination of loading)
  • Testing of the sensor response after integration in to the substrate material
  • Data analysis to understand the proper data visualisation for the novel material
  • Improvements of the electrical circuit while testing to include four-point electrical measurements as well as the incorporation of a Wheatstone bridge

 

Acknowledgment

We would like to thank the Federal Ministry for Economic Affairs and Climate Action (BMWK) for funding of the project ZIM Plug&Sense (KK5055907ZG0).

Authors: Jeanette Ortega Thomas Gries

Contact:

ITA Institut für Textiltechnik der RWTH Aachen University
Otto-Blumenthal-Str. 1
52074 Aachen

TPU CNT Melt spinning strain sensor bicomponent

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(c) ITA
27.09.2022

ITA Institut für Textiltechnik der RWTH Aachen University

Melt spinning of guitar strings made of Nylon 6 and measurement of their material properties

Fibres Textile machinery

Abstract

Monofilaments made of the polymer polyamide 6 (PA6) are produced using a laboratory sized melt tester and a drawing machine in a subsequent process. The influence of the production parameters spinneret hole diameter, draw down ratio and drawing temperature are investigated using a factorial design plan. To evaluate the melt spinning process, the spun filaments are compared to commercial nylon guitar strings. Mechanical and thermal properties such as filament titer, tensile strength, relaxation behavior, degree of crystallinity, melt temperature and melt enthalpy are measured to evaluate the quality of the production process. Four of the eight spun filament types are able to withhold the tension needed to tune the string to the correct pitch. Thus, these monofilaments could be used as guitar strings. The production parameter with the highest impact on monofilament quality is the draw down ratio, followed by drawing temperature. No effect was found for spinneret hole diameter.

Report

Introduction
Synthetic fibers have become increasingly important in recent years. One reason for this is that they are versatile and can fulfill different requirements and functionalities. Among other things, their functionality spectrum is influenced by the manufacturing process, for example melt spinning. One everyday application example for synthetic fibers is guitar strings.

Classical guitar strings are monofilaments made of nylon, which is the trade name of polyamide. They are usually designed to be used with guitars which have a scale length of 0.65 m. Of the six typical guitar string, the first and highest string is the high E string. It is usually tuned to a pitch of 330 Hz and has a diameter around 0.7 mm. Many acoustical properties of guitar strings can be linked to mechanical properties of the string, which are measured in this work.

The aim of this paper is to evaluate the melt spinning process of monofilaments of polyamide 6 and to compare them to commercial monofilaments. Therefore, the influence of different production parameters on the quality of monofilaments will be investigated. The considered production parameters are spinneret hole diameter, drawing temperature and draw down ratio (Ddr). Different kinds of mechanical and thermal properties, for example tensile strength, relaxation behavior, degree of crystallinity and melt temperature, are measured and compared for different filament types.

Authors: Ortega, Jeanette Karen; Zhao, Jasmin; Storm, Annegret; Schüll, Elena; Gries, Thomas

Contact:

ITA Institut für Textiltechnik of RWTH Aachen University, Otto-Blumenthal-Strasse 1, 52074 Aachen, Germany

Polyamide 6 Melt spinning Guitar strings Mechanical properties Drawings

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