Producers of manmade cellulosic fibres would like us to believe their wood-based yarns possess performance properties that make them suitable alternatives to polyester and polyamide. Does this theory have legs? Should sports apparel brands reconsider their fibre choices, or not?  

When Swiss chemicals company HeiQ announced the launch of its first fibre technology, AeoniQ, it boldly proclaimed that this cellulosic yarn derived from ‘climate positive’ raw materials could be a viable alternative to conventional synthetics. Shortly afterwards, Austrian manmade cellulosic producer Lenzing launched a programme promoting its Tencel lyocell fibre as a “sustainable and circular solution” for outdoor and activewear. These claims go against common practice in performance sportswear where polyester, and to a lesser extent polyamide, have long been the go-to raw materials for apparel designed to manage moisture, protect from the elements and keep wearers comfortable in their active pursuits. To see if the viable alternative theory has any legs, a panel talk at Performance Days in April brought together representatives from HeiQ, Lenzing and Optimer, the maker of Drirelease, which specialises in performance yarns made from blends of synthetic and non-synthetics.

Petrochemical fibres have progressively come to dominate fabric compositions for apparel applications. Synthetics made up 64% of global production in 2021, with polyester representing roughly 54% and nylon nearly 6% of all textile fibres produced. The share of manmade cellulosic fibres was 6.4%, including 5% for viscose, as per the Textile Exchange’s Preferred Fibre & Materials Market Report for 2022. The document does not break down usage by market, but it can be surmised that the proportion of synthetics in activewear would be higher, possibly in a range of 70% to 75%.

However, the manmade cellulosic fibres (MMCFs) landscape is ever evolving, with the arrival of new players on the market, such as Renewcell, Infinited Fiber Company, or even Spinnova, in addition to HeiQ. This family of fibres derived from cellulose pulp is also considered an alternative to cotton that could be more sustainable and less taxing on natural resources. For these reasons, among others, MMCF production is projected to rise to 10 million tonnes in the next 15 years, up from 7 million tonnes made in 2021. This prospect is not unanimously viewed as a good thing. Canopy, a Canadian NGO, says that more than 300 million trees are logged every year to manufacture cellulose pulp for fibres and fabrics.

The matter of cost

Synthetics are economically mass-produced, as Aswin Jaju, general manager for Drirelease, says, and this is the first reason evoked to explain their widespread use in activewear and beyond. “Furthermore, their primary property is hydrophobicity, they do not absorb water, they dry fast, and thus provide comfort. This is why synthetics excel in performance clothing,” he says. However, he notes that the rise of athleisure has favoured fabrics having a softer, more natural hand-feel, and “this is where regenerated cellulosic fibres come into play”.

The low price of polyester is the result of years of investment in developing efficient industrial- scale processes, which have also been directed at the recycling of PET plastics into polyester fibres to address activewear brands’ growing demand for recycled materials.

Lenzing has been manufacturing fibres derived from wood pulp for 80 years now, points out Andreas Gürtler, the company’s senior manager for functional wear. It has also optimised its processes over the years. It introduced Modal in the 1960s, which he describes as a “modified viscose fibre” (Modal for modified) having a higher wet modulus and better strength. “Our latest generation fibre is Tencel lyocell, which is produced using a non-toxic solvent,” he says. The name Tencel, he adds, refers to tenacity, implying it is a stronger cellulosic fibre. “It has a round cross section,” he adds. This gives it a smooth surface that bacteria do not attach to. “It is also antistatic, which makes it a good partner for blends with synthetics, as it discharges static electricity.”

HeiQ announced the launch of its cellulose-based fibre in late 2021. Carmen Danner, director of business development, says it will be cost-competitive when production reaches industrial scale, expected in late 2025. “It is a matter of scaling up feedstock and the manufacturing process. When we achieve mass volumes, prices will be lower, like polyester,” she says. HeiQ’s process and non-toxic biobased solvent are different from conventional manmade cellulosic fibres, she adds, without revealing more details. HeiQ AeoniQ is currently available in limited quantities and Hugo Boss introduced a first commercial product made from it earlier this year.

What about wicking?

The wicking and fast-drying properties of synthetic fibres make them ideal for activewear goes the consensus. Following this logic, the high moisture absorption of cellulose-based yarns would make them unsuitable for performance sports apparel, but this thinking may be ripe for re-evaluation.

Founder of fabric developer Concept III, David Parkes, worked with Performance Days founder Marco Weichaert, to help Lenzing develop the first Tencel-based outdoor fabrics collection. He points out that Tencel possesses genuine thermal properties and moves moisture away from the body. “It has very nice aesthetics,” Mr Parkes says, “it brings a lot of body to a textile and drapes well. The industry is concerned about rPET availability in the years to come and needs a replacement for polyester. Tencel could be that fibre,” he says.

Lenzing explains that Tencel lyocell’s ability to absorb moisture throughout its structure endows it with functional and comfort properties. The sub-microscopic canals between the fibre’s nanofibrillar structure are said to regulate the absorption and release of moisture. “Due to the porous structure of the lyocell fibre, moisture is distributed throughout the fibre. It won’t feel wet, and in combination with other fibres, it moves moisture away from the body,” says Mr Gürtler. To achieve best results, he says Tencel lyocell should be combined with a suitable “partner fibre”, which can be cotton, hemp, wool or polyester. Double-layer knits are cited as a fabric construction that will speed up wicking. “In most cases, for performance apparel, we see Tencel lyocell as a blending partner for other fibres,” he says. 

HeiQ has yet to test AeoniQ’s functional characteristics for activewear applications. Ms Danner says it will have properties similar to cotton, and these can be modified by finishing. “We are working on a permanent solution,” she tells WSA, and the project is only 15 months old, she points out. The first commercial product, launched with HeiQ’s brand partner Hugo Boss, is a next-to-skin polo shirt. A series of citywear fabrics, developed with Italian weaver Beste, were exhibited at Milano Unica in February. “AeoniQ can be used in a wide array of woven or knitted products. At the moment, we do not see any limitations,” she says. She also suggests that a yarn can be given different performance properties during spinning.

Sophisticated spinning

Drirelease performance fibres are based on “an optimised blend of hydrophobic materials, primarily synthetics, that we combine with a small amount of natural fibres to boost wicking and offer fast drying properties,” says Mr Jaju. The inherent comfort of cellulose-based fibres, such as cotton, is due in part to the subtle variations in texture of the natural fibre. “We try to mimic those natural variations by incorporating multidenier and multistaple polyester fibres within the yarn,” he explains. Drirelease yarns are generally made from blends of 85% to 90% polyester or nylon combined with 10% to 15% natural or cellulosic fibres. This proportion, he says, “provides the optimum balance of wicking and fast drying. The natural or plant-based fibres channel moisture within the yarn structure, and the hydrophobic fibres drive that moisture out, in a push-pull system without any chemical finish. Because these properties are engineered in the fibre blend, the yarn offers permanent performance.”

In addition to cotton and lyocell, Drirelease yarns are now available in a host of other fibre compositions, including hemp. The newest product in the range incorporates recycled cotton, from Recover. The next one to come will be a blend with a pineapple fibre, supplied by a company based in Thailand. Optimer has recently expanded its hydrophobic-hydrophilic concept with a new technology called Dricomfort Geo. “We enhance the performance of filament polyester and nylon fabrics that are hydrophobic by adding a mineral particle infusion that is hydrophilic. This mineral particle infusion provides the channel to absorb moisture and heat drives the humidity out at a faster rate,” Aswin Jaju tells WSA.  

Biodegradability & recyclability

Moisture management and wearer comfort thus appear to be obtainable and controllable via fibre blend, spinning or finishing. But in a market increasingly driven by eco-responsible concerns, brands and their buyers also seek to offer product ranges that have a ‘clean’ end of life. This holistic vision could give cellulose-based materials the upper hand when considering biodegradability or recyclability. Both Lenzing and HeiQ have tested their fibres’ ability to disintegrate in soil. Lenzing has found that a Tencel lyocell knitted fabric will decompose completely in 14 weeks in compost, and similarly disintegrates in sea water, in tests conducted off the coast of San Diego. HeiQ’s in-house laboratory has found that a cellulose-based knit made from AeoniQ will biodegrade in 10 weeks. Synthetic fibres and fabrics cannot compete on this, unless an additive is incorporated into the polymer to speed up degradation.

With regards to recyclability, Carmen Danner insists that HeiQ AeoniQ can be recycled “eternally”, though this “depends on various factors,” she says. “But the fibre ultimately needs to biodegrade at the end of its lifecycle.” HeiQ and Lenzing can both incorporate pulp recycled from used cotton-rich textiles to make their fibres. They have also both formed partnerships with Renewcell to integrate Circulose pulp into their production processes. Lenzing’s Tencel lyocell with Refibra technology is made from a blend of wood and cotton pulp.

Likewise, at HeiQ, pulp derived from used cotton can be used to make AeoniQ. “Our process is very flexible with regards to feedstock, we have already started using pre- and post-consumer waste and we are in trial phases with Renewcell, Evrnu and Circ,” says Ms Danner. She adds that AeoniQ is a filament fibre, which means it is more durable and it may generate a higher-quality fibre once recycled, compared to a staple fibre.

On these two topics, Mr Jaju points out that there are different ways to envision sustainability. A synthetic yarn will not biodegrade, unless an additive is incorporated into the fibre, but he says that with regards to durability, synthetics are peerless. “If you take a recognised durability standard, such as the Martindale abrasion test, a synthetic fabric will resist rupture long after a cellulose-based textile. A synthetic garment can be worn longer and that helps reduce its overall impact,” he notes.

Recycled polyester (rPET) may often be favoured over its virgin counterpart, but its uptake is slow; it inched up from 14.7% to 14.8% of global polyester production in 2021. It faces the challenge of switching from an open- to a closed-loop system by replacing PET plastics with used polyester textiles. While both synthetics and cellulosics can theoretically be recycled, mechanically or chemically, in practice the industrial infrastructure to do so is far from reaching a scale that would bring either of them into the mainstream.

There is also a global move, among sports brands and beyond, to favour plant-based materials derived from renewable resources over those made from fossil fuels. This argument gives manmade cellulosic fibres another advantage.

Ultimately, choosing to favour one or the other category of fibre will depend on the use case of a finished garment, whether it is designed for extreme conditions or as a lifestyle item of clothing. Yet, unpacking their relative properties does seem to open the door for an increased presence of manmade cellulose fibres in activewear.

Initially positioned for the fashion market, Tencel lyocell was found by Lenzing’s R&D department to have many properties suitable for active sportswear: a smooth surface, a cooling effect, bacteria resistance and moisture absorption throughout the fibre.  
Credit: Lenzing 

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