There’s no getting away from the fact stretch fibres add comfort and shape for a certain segment of the denim market. While baggier styles have dominated the younger market for some time, stretch denim will always be in demand for women’s styles and might even become more prevalent again, if the recent inclusion of skinny jeans on catwalks is anything to go by.
Stretch fibres might only typically make up 2% of the fabric, but the addition of synthetic fibres from non-renewable sources increases the manufacturing footprint and blending elastane into cotton makes end-of life-solutions tricky. There are currently no widescale or easy ways to break down and recycle these blends – although progress is being made through R&D. As trials continue, Lycra and Hyosung have changed tack, looking for natural ingredients to add into the formula, and Yulex is hoping the rubber tree can provide an alternative option.
While Italian mill Candiani was the forerunner in the natural stretch space with the launch of its Coreva denim in 2020, Yulex has had its eye on the denim market for several years. The company has its roots in US-based Yulex Corporation, which spent years developing natural rubbers from guayule shrubs in Arizona, seeking to establish a US supply chain. Founder Jeff Martin and the team worked with outdoor brand Patagonia on an alternative to neoprene, and the companies launched guayule rubber-containing wetsuits in 2013.
Fast forward just over a decade and Yulex has been busy: it has changed its raw material to latex extracted from rubber trees, then moved its supply chain from plantations in Sri Lanka and Guatemala to South East Asia. This summer, it launched two new products: Yulex2.0, a stretchier version of its foams, and a stretch filament, Yulastic, billed as an alternative to elastane for the denim market, socks and elastics.
The change of supply chain was partly driven by a desire to boost R&D by diversifying its manufacturing partners, but also to be closer to the footwear and clothing manufacturers in Asia, thereby slashing carbon emissions. For Mr Martin and now-CEO Liz Bui – who was born in Vietnam but immigrated to the US as a child after the war – that meant moving to Asia and travelling around Vietnam with organisations such as the Programme for the Endorsement of Forest Certification to galvanise cooperatives of rubber farmers. “For these smallholders, their livelihood and their household income is derived from the small plot of land in their backyard,” Liz Bui tells us. Yulex now works with more than 240 smallholders in Thailand and 1,500 in Vietnam and has set up an Equitable Agriculture profit-share programme to provide better security of income for the farmers.
Tree latex consists of rubber particles or biopolymers but also contains dirt, oil, proteins, metals and other impurities. Yulex has proprietary technology and works with its partners’ systems to remove the proteins and impurities. The purified latex is branded as Yulex Pure, and is used to make Yulastic filament. Following trials at mills in Asia, and in consultation with technical specialist and general manager Idrish Munshi, the company can now offer a fine-denier filament, with ultra-fine deniers in development. Yulastic filaments have similar properties to elastane and also recover well, according to Dr Bui. “Natural rubber is a very good polymer – consider that aeroplanes have to use 100% natural rubber for their tyres,” she comments. “We focus on the performance first, and Yulastic is 100% biobased so it also has a good sustainability story, that is a bonus.”
The company is expecting to have fabric samples with mill partners ready in the New Year. “What we want to offer is choice,” adds Dr Bui. “We are working with experts, key opinion leaders and denim manufacturers to develop this. What is going to be important is which brands adopt it first.”
There is a similar focus on natural raw materials from Korean group Hyosung, which, earlier this year, announced a $1 billion investment in bio-based butanediol (BDO). The bio-BDO will be made using a process developed by US-based biomaterials developer Geno, and the funding will enable the building of a new manufacturing facility in Vietnam to enhance Hyosung’s existing site and create a full-service chain from raw ingredient to fibre.
Conventional BDO, often made from coal from China, is used to produce 2.5 million tonnes of polymers every year and is a $5 billion a year industry, according to Geno’s estimates. BDO is a precursor to PTMG, a major chemical intermediate that can be used to create everything from automotive plastics to electronics and shoes, and is combined with a smaller amount of MDI to make elastane. Geno’s technology uses various forms of sugar sources – industrial corn, sugarcane and sugar beets – and licenses the know-how to chemicals or fibre groups. “We provide the entire package, including engineering designs and the microbe that does the magic inside the fermentation tanks, converting sugar into BDO,” says Christophe Schilling, CEO of Genomatica.
Earlier this year, Hyosung received approval from the provincial government in southern Vietnam to produce bio-BDO at its factory in southern Ba Ria-Vung Tau Province, manufacture PTMG at a nearby factory in Dong Nai and then use this to mass-produce Regen Bio elastane at the Dong Nai spandex factory. It will mean the raw material will be derived from sugar cane, not the industrial corn that it is currently using for its bio offering. “Although we will have to import the sugar cane from suitable supply chains, we will have a plant that can then make the whole product to the finished elastane, so that will mean a significant reduction in carbon emissions, as we are doing it all in one site,” Hyosung’s global sustainability director, Simon Whitmarsh-Knight, tells Inside Denim.
Hyosung commercialised biobased elastane made with 30% industrial corn in 2022. It has a 20% lower carbon footprint than a comparable conventionally made elastane, according to a lifecycle assessment, and performs in the same way. Its current biobased elastane offering now includes options made with higher bio-based content, with LCAs due soon.
Geno’s technology also underpins Lycra’s bio-derived offering: the company is going full steam ahead with creating an elastane with 70% renewable feedstocks – industrial corn – since partnering Qore, the maker of a BDO alternative called Qira and a joint venture between chemicals firm Helm and food corporation Cargill. Edible sweet corn makes up less than 1% of the corn grown in the US; most goes into industrial uses such as animal feed and ethanol while the starch goes into adhesives, packaging and fibres. Lycra’s development will bring income to the corn farmers in and around Ohio, many of whom operate family-run businesses and half of whom use wind-generated power.
One such supplier is Kuiper Farm, where Steve Kuiper operates a corn/soy bean rotation, incorporating rye as a cover crop, which builds organic matter and keeps the soil fertile. “One thing people don’t realise is that a big chunk of products that are made from petroleum can be directly replaced with products that are made from corn,” he says. “You can produce 4,000 different things out of corn, and I’m excited about our products being used in sustainable fashion.”
It is the corn’s starch that is used as a building block for Lycra’s fibre. Cargill’s biotechnology campus in Iowa will turn the corn into Qira, next supplying to Taiwan’s Dairen Chemical Corporation, which will use Qira to make PTMEG, before heading to Singapore to be made into bio-derived Lycra fibre. Replacing non-renewable-derived content with Qira could reduce the fibre’s carbon footprint by as much as 44%, according to a lifecycle assessment.
The bio-derived Lycra fibre will consist of 70% renewable content derived from dent, or grain, corn and will be available at a large scale in 2025. It will deliver equivalent performance to traditional Lycra fibre and will help reduce customers’ carbon footprint. “Our message to denim brands is clear: transitioning to bio-derived Lycra fibre isn’t just a step forward in sustainability but also a way to stay competitive amid sluggish market demand,” says Ebru Ozaydin, global marketing director for denim and wovens at Lycra. “As sustainability becomes a core expectation rather than a luxury, denim brands will want to integrate innovations like bio-derived Lycra fibre into their production to ensure they remain resilient, accountable and flexible in an evolving market.”
With manufacturers and suppliers investing heavily in R&D and more sustainable products, there is a nervousness in some sectors about whether buyers will place the necessary volumes to fund their production and development. A slew of incoming regulations that will demand a more sustainable footprint for products sold in Europe should provide the nudge many are waiting for. “We will also need to see two or three leading retailers and brands really get behind new technologies, as that will then make the real difference. That needs strong leadership,” says Mr Whitmarsh-Knight. The digitalisation of the supply chain, as companies prepare for Europe’s Digital Product Passport, should also boost ‘lower-impact’ textiles, as materials and ingredients will be more transparent and trackable, he suggests.
The need for more ‘sustainable’ versions of elastane is pressing, as the global apparel market grows. Although elastane makes up only around 1% of global fibre production, it carries “outsized importance” given that it is found in a large volume of products, according to the US-based Textile Exchange. In its 2023 Materials Report, the non-profit said elastane fibre production is increasing slowly but steadily, rising from 1.16 million tonnes in 2021 to 1.24 million tonnes in 2022.
Despite millions of dollars pouring into research around the recycling of elastane, it remains a sticking point, quite literally in some regards. Lycra used the Dornbirn Global Fibre Congress in September to update the market on its “promising results” on separating and making new Lycra fibres from textiles. “We have also designed a new Lycra fibre product that in the future can further ease this process. Everything is in lab stage for now but quite promising,” Alberto Ceria, Lycra’s senior applications development manager, tells us. “Bio-derived and recycling are independent programmes but our long-term vision is to converge and integrate these technologies together.”
A similar sentiment at Hyosung, where Whitmarsh-Knight says the ultimate goal is to make elastane with renewable resources and also have the technology to make it recyclable. “The industry is still looking at various sustainability options – is recycled better, or biobased, or is it something completely new coming down the line?” he adds. “Until the industry decides to go down one avenue, we want to offer a complete range of solutions.”
