Design Potential of Technical Hemp and PLA Nonwovens

ABSTRACT

The main purpose of the article is to present the potential use of hemp fibers as reinforcement in composites, but from a design perspective. The authors ask whether sustainable nonwovens, produced based on natural fibers, have the potential as a material for designers and artists and not only as a technical textile. Technical production of nonwovens like carding, punching and laser cutting was used to achieve not just functional, but also aesthetic quality of the samples. The possibilities of utilizing natural materials for design endeavors were presented. The production process of these items was described, along with the main design concept. Research was carried out through a series of interdisciplinary activities, using the knowledge and tools typical for textile and materials engineering, as well as the methodology and strategies derived from the fields of visual art and design. It has been shown that during the development of a new sustainable material significant attention should be paid to design aspects, so it shows its full potential, as not just being eco-friendly, but also functional and aesthetic. While technical hemp and PLA composites have been produced and studied before, the design aspect is unique in the current study.

摘要

本文的主要目的是从设计的角度介绍大麻纤维在复合材料中作为增强材料的潜在用途。作者询问，基于天然纤维生产的可持续非织造布是否有潜力成为设计师和艺术家的材料，而不仅仅是一种技术纺织品. 采用梳理、冲孔和激光切割等技术生产非织造布，不仅实现了样品的功能性，而且达到了样品的美观性. 介绍了利用天然材料进行设计的可能性. 介绍了这些产品的生产过程，以及主要的设计理念. 研究是通过一系列跨学科活动进行的，使用了纺织和材料工程的典型知识和工具，以及视觉艺术和设计领域的方法和策略. 研究表明，在开发一种新的可持续材料的过程中，应特别注意设计方面，使其充分发挥其潜力，不仅环保，而且功能和美观. 虽然以前已经生产和研究过技术大麻和聚乳酸复合材料，但在目前的研究中，设计方面是独特的.

KEYWORDS:

• Hemp fibers
• PLA
• nonwovens
• composites
• laser-cutting
• design

关键词:

• 大麻纤维，PLA
• 非织造布
• 复合材料
• 激光切割
• 设计

Introduction

Sustainably produced materials, in most cases, carry limitations, both functional and aesthetic. The research project was guided by the assumption that the involvement of artists/designers at an early stage of engineering work can affect the design potential of the new material and thus facilitate its use at the stage of its commercialization.

The project, undertaken by the teams from the Lodz University of Technology (Poland) and University of Borås (Sweden) was interdisciplinary (art/design and materials engineering) and carried out in the frames of the Horizon EU funded research grant. Its main goal was to analyze sustainable nonwovens, produced on the basis of natural fibers, in terms of their potential as a material for designers and artists and not only as a technical textile. The majority of undertaken activities were focused on the analysis of the natural fibers, nonwovens and composites and the selected sustainable finishing techniques, in terms of their design potential – functional and decorative. The aim was to develop a number of samples that can be treated as a “pattern book,” exemplifying particular design solutions.

The main natural fiber to produce the nonwoven was hemp, mixed with PLA. The tested nonwovens possess qualities that make them an attractive material for artists and designers. They should replace polyester nonwovens that are very popular at the market, due to much higher sustainability, but also because they offer a much more natural feel.

Nonwovens made of hemp and PLA fiber blends have been reported in literature for technical use in several applications. One study reported the production of hemp-based barrier papers in a film coating method. Alkali-treated hemp fibers were used for the paper preparation process then were coated with PLA films (Cetin et al. 2022). High-insulation capacity hemp nonwovens were produced using wet-laid technology and PLA used was compatible with wet-laid production methods. The structures were made using hemp waste from spinning process and showed to have a low thermal conductivity when blended with PLA and viscose (Gutierrez-Moscardo et al. 2022). Scaling up the production of bio-composites of natural hemp fiber (hemp)-filled with different types of PLA was reported to facilitate the commercial production of technical composites based on different structures including nonwovens (Wang et al. 2022). Recent studies reported the use of these blends in the production of nonwoven mulches for weed control without harming the environment (Kopitar, Marasovic, and Vrsaljko 2024; Marasović et al. 2023). Other technical applications related to food, textiles and packaging were reported in the literature using hemp and PLA blends in different forms including nonwovens (Promhuad et al. 2022). Hemp hurds were used as bio-sourced additives in PLA-based composites, these materials showed great potential to be used in green and sustainable packaging applications (Momeni et al. 2021). Other technical applications and characterization of mechanical properties of hemp-PLA blends have been reported in the literature (Senthilkannan, Miguel, and Gardetti 2020). Additionally, hemp hurds and other bast fiber blends such as flax composites have been studied from a technical perspective (Lemmi, Barburski, and Samuel 1470–9589; Poniecka, Barburski, and Urbaniak 2022; Vanleeuw et al. 2015).

However, and to the best of our knowledge, these blends have not yet been fully explored for their potential as an artistic element for design purposes. Hemp has great versatility regarding its natural colors that can be different based on the maturity levels, time of harvest and extraction methods, which allows the use of naturally colored materials with green, yellow and earthy tones when needed. When bleached in a sustainable manner, hemp has the ability to be dyed with attractive colors as well. Paired with its other mechanical, thermal and acoustic properties, it can be a material with great potential for designers working with home décor and interior elements and other applications, i.e. textile and fashion design. Herein, we propose an interdisciplinary take on these nonwoven blends to be used in designing applications.

Materials and Methods

The assumption of the project was to work with sustainable material that would be the combination of natural fibers with PLA, so it can be used both as a non-woven and a composite. The team in Borås has already been researching hemp, so this fiber has been chosen as the main component.

During the project, the artist was trained to produce the nonwoven fabric from raw fibers. The cottonized hemp used was harvested in Poland and chemically cottonized with alkali treatment. The mean length of these fibers is 23,1 mm with a short fiber count of 12,6%. These fibers possess an elongation Emax of around 4% and 35 ± 10 dTex as linear density. The number of samples for the linear density measurement test was N = 10. Fiber characterization has been conducted using Fibrolength and FAVIMAT+ instruments by TexTechno-German.

The fibers (in desirable proportions) had to be processed through the opener machine to make the fibers looser and softer for better blending. Fiber opening was conducted on lab scale opener using a modified (Laroche) fiber opener. The next step was carding. The purpose of this process is aligning the fibers parallel to each other, blending them by intermixing, and removing most of the remaining impurities. The end result is a smooth even batt ready for further processing, like needle punching or heating. It is worth mentioning that in laboratory conditions the distribution of two types of fibers, even in the machine process, is done manually to some extent, so it is difficult to control.

The proportions of fibers were variable with minimum 40% of PLA to maintain the possibility to obtain a composite as a final result. PLA used to prepare the samples mentioned in this article is a type 400 crimped fiber which has a length of 60 mm, with 6,7 dTex linear density. PLA was provided by Trevira GmbH, Germany. Most of the produced samples were 50/50 hemp and PLA fibers. The next step in the preparation of nonwovens is needle-punching. During this process, the fibers are bonded together mechanically by fine needle barbs, through fiber entanglement and frictions. The needle punched nonwovens were produced with HUNTER Fiberlocker Lab Needle Punch, 11” wide. The number of needles in the bed is 969 needles provided by Groz-Beckert. The effective width of the machine is around 25 cm. The nonwovens produced were with different thicknesses and densities, the stich density used was constant and equal to 70 stich.cm⁻².

In the project needle punching was used to prepare nonwovens for dyeing, so they would hold a compact structure while in the liquid environment. In other cases, like for laser cutting, thermal bonding of the carded web was sufficient to make the nonwoven, without the need for previous needle-punching.

Thermal bonding methods for the nonwoven made of thermoplastic fibers include simple heat-pressing in app. 180°C. The size of the heat-press determines the size of the sample, so in the case of this project, heating was also performed with the use of an iron. This allowed for making bigger pieces and working with greater control on more complicated elements.

Some samples were prepared from the nonwoven that was dyed in order to introduce color into the design. For hemp + PLA nonwoven, it was chosen to dye with reactive dyes, due to this method’s simplicity, allowing for mixing various colors and space dyeing. Reactive dyeing is the most common low-impact synthetic method to dye cellulose fibers. The dye is forming a permanent attachment in the fiber so it becomes part of the fiber, leading to the good color fastness to wash. The fabric requires soaking in the soda ash solution before pouring on the dye solution. Due to the PLA component in the fabric, the resulting colors were slightly less intense than they would be with pure cellulose fibers, but the results were still quite satisfactory. The colors were not so vivid after drying, but looked natural.

The initially prepared pieces of nonwovens (natural or dyed) were later processed with other finishing techniques: cutting, laser-cutting, pleating, and further thermal-bonding in order to test various surface effects.

The main tool used at this stage was the laser cutter. It is a device used to cut various types of materials, such as textiles, wood, metal, plastics or composites up to a thickness of approx. 50 mm. The plotter is computer controlled, thanks to which it is possible to cut elements of a specific, same shape and size. The settings for cutting using laser cutting varied a little according to the thickness of the material as the samples were not 100% consistent in this respect. The general settings for cutting hemp/PLA nonwovens were 600 pulses per inch. To prepare images for laser cutting as vector files Adobe Illustrator software was used.

Thanks to the workspace of the 60 × 90 cm size, it was also possible to cut larger elements for product prototyping. The engraving function was used for the surface decoration. As part of the project, the plotter was used for cutting previously designed patterns at the tested material, which enabled obtaining repeatable results. This type of device is a very popular tool in the industry and widely used for cutting polyester nonwovens. It was therefore important to test how the researched materials would respond to this kind of treatment.

Working with a new material on a laser cutter requires many tests and adjustments of settings, so the speed and power of the laser are proper for the density and thickness of the material. It turned out that hemp + PLA nonwoven is a very suitable material for laser-cutting when it is properly prepared and the settings of the machine are right. Preferably, the non-woven has to be initially processed with thermal bonding, so it has a consistent structure without any fluffy parts or air pockets, because it would cause a fire hazard. This actually occurred during the trials to laser-cut flax + PLA sample because it probably had too loose structure. The hemp + PLA material also turned out to be a very good substrate for engraving. It was possible to achieve a very fine and legible marks on it.

Some samples – one to three layers of nonwovens composed together – were then heat-pressed (180°C) under high pressure to make composites. As the press was a typical small size laboratory equipment, it was only possible to make samples of the size 18 × 18 cm. This allowed us to compare the surface qualities of the same samples – as nonwovens or heat-pressed into composites.

Results

Nonwoven samples

The design process was strongly influenced by the material and its properties. Initial steps were oriented toward understanding the material and playing with it, without much conceptual planning. In order to explore the thermoplastic quality, some trials were made with combining the nonwovens – as carded webs or more solid needle-punched fabric – with some waste textile material from the weaving lab – yarns and scraps of fabric, by heating the layers with an iron. It turned out that with thin layers the material becomes translucent which can be used to achieve some interesting effects when it is backlit. With hand ironing it was also possible to gradually add the materials in order to achieve the desirable effect (Figure 1)

Figure 1. Nonwovens with some waste textile material [photo: K. Zimna].

The leading finishing technique chosen for this project was laser-cutting of the nonwovens, because it supported the idea of working with layers, exposing translucency of the material, playing with colours and well-defined patterns. It also corresponded well, by contrasting, with the natural, organic character of the nonwovens. This main technique was supplemented with dyeing methods that allowed to incorporate colour in some layers. Some samples were also made using scrap materials from other samples – cut-off stripes or laser-cut remains of patterns. (Figures 2–8)

Figure 2. Simple one-layer laser cut sample, hemp + PLA nonwoven [photo: K. Zimna].

Figure 3. Thermal-bonded two layers of laser-cut hemp + PLA nonwoven [photo: K. Zimna].

Figure 4. Three layers bonded together: laser-cut hemp + PLA nonwoven, dyed wool + PLA, hemp + PLA nonwoven. This sample was heat-pressed for 10 minutes 180 Celsius, so the layers started to blend together, but not yet formed a composite [photo: K. Zimna].

Figure 5. Sample made of thermo-bonded left-over scraps of laser-cut hemp + PLA nonwovens [photo: K. Zimna].

Figure 6. Sample made of pleated and thermo-bonded left-over scraps of hemp + PLA nonwovens [photo: K. Zimna].

Figure 7. Sample made of thermo-bonded left-over scraps of hemp + PLA dyed nonwovens [photo: K. Zimna].

Figure 8. Laser engraving on hemp + PLA nonwoven [photo: K. Zimna].

Composites samples

The above samples were bonded using iron or heatpresses. In the heatpress, when processed for about 20 min in 180 Celsius degrees, the nonwoven would gradually become more solid and would eventually turn to become something more like a composite. The PLA fibers were melted at a high temperature, which resulted in the impregnation of hemp fibers. For a full composite there was still not enough pressure applied, so composite samples were made in the Polymer Lab in a press with applied pressure of 2MPa, in 180 C, for 4 min (Figures 9–10).

Figure 9. Hemp/PLA pleated sample composite, uneven distribution of PLA can be observed [photo: K. Zimna].

Figure 10. Composites made of different nonwoven samples [photo: K. Zimna].

Figure 11. Product sample – a lampshade made with PLA and hemp laser cut nonwovens [photo: K. Zimna].

The hemp and PLA nonwovens, thanks to the translucency of thin layers, the possibility of thermal bonding and the natural look, can be applied by the designers for all sorts of products, such as for example lamp shades (Figure 11). The above sample shows visual qualities of the material and the possibility of unlimited variations when playing with its parameters, such as: thickness, number of layers, color. The material also presents good compatibility with other finishing techniques, such as dyeing, cutting, engraving, embroidery or printing. Thanks to such a wide range of finishing methods that help to achieve different visual effects, this material could be used in interior, fashion or even automotive industries. Undoubtedly further development is needed, especially regarding impregnation and washing issues.

Discussion

The tested nonwovens possess qualities that make them an attractive material for artists and designers. They should replace polyester nonwovens that are very popular at the market, due to much higher sustainability, but also because they offer a much more natural feel.

The combination of hemp fibers with PLA presents an alternative to nonwovens made with oil-based fibers such as polyester, with lower environmental impact. Hemp and PLA nonwovens are obtained from renewable resources, biodegradable in their pure form and offer a variety of colors and textures based on the used hemp and its natural hints of earthy tones when dyeing is not performed. This blend shows great potential as a sustainable alternative in replacing fossil-based thermoplastics in design elements.

During the two-month stay, all initial goals were fulfilled. A design-oriented hands-on analysis of the material was performed. It was a great advantage to be able to produce samples of the material with desirable composition and proportions of components, thickness and the way of manufacturing for particular tests. The samples for the “pattern book” for the selected sustainable finishing techniques were produced. The techniques included: dyeing with reactive dyes, laser cutting, engraving, bonding different layers of material, recycling left-over scraps from laser-cutting. Selected samples were later heat-pressed under high pressure to make composites. Most research and design work was focused on nonwovens and their applications, but the follow-up research should be focused on composite samples. At this stage, there is little control over the distribution of PLA in the sample, layers and color blending. However, there is a great potential for application of this material in design projects, especially because parts of the design or particular layers can be combined together only with the help of heat, without any other bonding agent. Further development should focus on washing and impregnation issues and the optimalization of the processes for mass production.

Conclusions

The world turns to the idea of sustainable development. The demand for composites reinforced with natural raw materials is growing, which is why hemp + PLA fibers were used in the research.

As a result of the research, the following conclusions can be drawn:

• The combination of hemp fibers with PLA presents an alternative to nonwovens made with oil-based fibers such as polyester, with lower environmental impact.

• Hemp and PLA nonwovens and composites are interesting materials for different design purposes; with further development can be applied in interior, fashion or automotive industries.

• Thermal bonding allows for attaching pieces or layers of the material together to obtain a final product without using any additional bonding agent or method, which is a great advantage from the eco design perspective.

• In the design of utility products, significant attention should be paid to visual aspects so that the product appeals to the user aesthetically as well. Artists/designers should be included in interdisciplinary teams working on new sustainable materials that are nowadays the fundamental aspect of eco design.

• The study can be treated as a pilot project pointing to the potential of the new material that needs further technological development to deal with the material’s limitations, especially washing issues, so it is suitable for commercialization.

Highlights

• The research project was guided by the assumption that the involvement of artists/designers at an early stage of engineering work can affect the design potential of the new material and thus facilitate its use at the stage of its commercialization.

• Hemp and PLA nonwovens and composites are interesting materials for different design purposes; with further development can be applied in interior, fashion or automotive industries.

• The combination of hemp fibers with PLA presents an alternative to nonwovens made with oil-based fibers such as polyester, with lower environmental impact.

• Technical production of nonwovens like carding, punching, dyeing and laser cutting was used to achieve not just functional but also aesthetic quality of the samples.

• Thermal bonding allowed for attaching pieces or layers of the material together to obtain a final product without using any additional bonding agent or method, which is a great advantage from the ecodesign perspective.

Acknowledgments

The authors express their deepest gratitude to the academic team from the University of Borås led by Professor Nawar Kadi and Professor Mikael Skrifvars, for their support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data presented in this study are available on request from the corresponding author.

Additional information

Funding

The research conducted by the authors was carried out as part of the project “Sustainable Industrial Design of Textile Structures for Composites”, which is funded by the European Union. Grant Agreement no. 101079009 Call: HORIZON-WIDERA-2021-ACCESS-03/Twinning. Acronym: SustDesignTex.