Change of gear for membranes
After years of incremental improvements in the performance properties of waterproof-breathable membranes, radical new technologies are coming to market. Manufactured without solvents, made from biobased materials or offering mono-material design possibilities, they are ushering in a new era of sustainable innovation.
A basic feature of performance outerwear is its ability to block rain and wind while letting moisture out. This was a key breakthrough introduced in the 1970s by Bob Gore, who passed away last year, and it is the defining feature of Gore-Tex fabrics. First-generation membranes tended to favour weather protection over wearer comfort, waterproofness over breathability. Over the years, the focus has gradually shifted to greater air permeability and moisture transfer for more active uses. These incremental tweaks in performance and in ever-finer market segmentations were the main news in this field. Change is in the air as a new generation of companies introduces more sustainable solutions, new polymers and manufacturing methods.
New options in polymers
Polyolefin and polypropylene are two of the new polymers in waterproof-breathable materials, expanding on the tradition of polyurethane (PU) and expanded PTFE (e-PTFE). Taiwanese tech conglomerate BenQ Materials has transposed a film technology found in computers and TVs to textiles to launch Xpore, an ultralight nanoporous membrane made from a polyolefin weighing a mere 5 to 6 grammes per square-metre and 12 microns thick. “Xpore is not only a membrane technology but also an adhesive and lamination technology,” says Rex Lee, head of the company’s performance textiles business unit. The film and adhesive are manufactured without solvents, offering a more eco-friendly process compared to similar materials, he says. Its performances are in line with industry standards, with waterproof levels that can go from 10K to 30K and even 50K (mm water column, ISO811), and breathability in the order of 10K (moisture permeability measured in grammes per square-metre per 24 hours, JIS-L1099A1), the company states. Launched in early 2020, Xpore has been adopted by French eco-brand Picture Organic Clothing. The company is currently seeking to introduce a 2.5-layer laminate.
Trenchant Textiles, also based in Taiwan, is another new player in the world of waterproof-breathable materials. It has chosen polypropylene for its Intrepid membrane. “Polypropylene polymer science has changed significantly in the last three decades. Key patents expired in the late 1990s and early 2000s, which has made possible a second coming for polypropylene,” CEO, Matt Cleary, tells WSA.
“Due to its crystallinity, polypropylene presents a homogenous and spherical porous structure that is ideally suited to blocking water and letting moisture pass through,” says Mr Cleary. “It has a unique biomorphic structure that is achieved without the use of solvents.” The ratio of matter to void in Intrepid is approximately 84%, meaning that it consists of far more air than material. Measuring 18 microns thick, it is remarkably light, weighing just four grammes per square-metre. Furthermore, if a brand chooses to bond an Intrepid film to a polypropylene face fabric with a suitably tight weave, it may not require a DWR treatment to offer protection from rain, the company claims.
This is exactly what Norwegian outerwear brand Helly Hansen has chosen to do in its new Lifa Infinity Pro range, launched last year with the polypropylene membrane. “It is a ground-breaking material that requires no additional chemical DWR and it aligns perfectly with our core Lifa-branded fibre,” said Helly Hansen category manager Philip Tavel at launch. “We have solved a problem that the entire outdoor industry has been looking at for years: to create a high-performance garment without using a fluorocarbon DWR finish.” The brand chose a dope-dyed face fabric to further reduce water and chemical use.
“This high-profile launch gives us a substantial base for development,” says Sandra Cleary, Trenchant Textiles’ chief operating officer. The possibility of creating a laminate in a single type of polymer is attracting the attention of companies looking to develop high-performance mono-material outerwear.
Mono-material laminates
KTC Lab, a division of China-based clothing manufacturer KTC, is looking to develop a range of sustainable and recyclable skiwear that will be available for rent from swissrent, a company with 31 dealers in 22 locations in Switzerland. “Skiwear is often worn just one week a year. It makes sense to rent these types of clothes, and in that case, we need a solution for them when they can no longer be worn,” says Monika Rausch, an independent designer and project manager for KTC Lab. A mono-material laminate would be easier to recycle than conventional multi-component ones.
The company is testing several options, including Trenchant Textiles’ Intrepid membrane. “The advantage of polypropylene is that it may not need a DWR finish, and this is a polymer that can be injection-moulded to manufacture trims, zippers and buttons,” says Ms Rausch. But the lack of an established collection and recycling system for polypropylene makes it less attractive, in the short term, compared to polyester. KTC Lab has another ongoing research project to develop performance skiwear using only recycled or recyclable polyester-based materials with wear2wear, a consortium of European companies seeking to close the loop in textiles and apparel.
Whatever the option, adhesives remain an issue, as polyurethane is the go-to solution for bonding. “Polyurethane is the most common adhesive and it is also present in fibre form to provide stretch and recovery. Mechanical stretch can only go so far,” the designer says, even though she believes it can be avoided in skiwear with clever tailoring.
Improving on electrospinning
The success of The North Face’s Futurelight launch in 2019 has attracted attention to electrospun membranes. These types of materials have a highly porous, nonwoven structure, which makes them very breathable. They will be less watertight, by nature, and have been slow to come to market. NTX, a company based in Singapore, believes its newly developed e-Nanofiber technology solves some of the issues relating to electrospinning.
The process developed by NTX is not based on multiple-nozzle needle-based systems that ‘spray’ or rather draw out a polymer to form a nonwoven film, but on a needle-less process, used in industrial filtration. “Our method is 70 times faster than needle-based methods and seven or eight times faster than needle-less ones,” says Jeffrey Hsu, NTX chief innovation and marketing officer. “As there are no nozzles, there is no clogging,” he points out. In addition to the “electrical control of the electrospinning process” that makes its e-Nanofiber unique, he says: “Our core innovation lies in a new extruder ‘driver’ that substantially increases surface area for fast ‘spinning’.”
NTX says the performance characteristics of its e-Nanofiber film can be tuned to adjust breathability and waterproofness. “These are, as always, a matter of compromise. Our process produces a highly air-permeable film, we can achieve greater waterproof capability by layering more nanofibre,” says Mr Hsu. He expects it to be launched by a performance sportswear brand in late 2021.
NTX’s e-Nanofiber process can also make face masks, currently in high demand. A new company based in Amsterdam, NTEU, was founded in December 2020 with European partners, to address this market. “Our system is a modular one; NTX e-Nanofiber can manufacture materials for soundproofing, filtration, PPE masks and membranes,” says Mr Hsu.
Biobased raw materials
During his studies at ETH Zurich, Dr Mario Stucki developed a new manufacturing process for membranes and founded Dimpora with fellow student Dr Anna Beltzung. The patent-pending technology has won Fashion For Good and Global Change awards, and is being introduced by Swiss ecobrand Rotauf this winter. This first iteration of the eco pur branded membrane is made from polyurethane, but the young company is exploring other polymers, including a biobased solution currently in tests by “a major sports brand,” says Dr Beltzung, Dimpora’s chief technology officer. The sustainability-minded company also plans to develop polyester and polypropylene versions to make it possible to create mono-material performance clothing. “We are screening different potential polymers, but we need to find the sweet-spot between waterproofness and breathability,” she says. A solvent-free manufacturing process for membranes is also in R&D at Dimpora.
Under new ownership, eVent fabrics, which commercialises an expanded PTFE film, is also working with new raw materials. In June 2020, Parker Performance Materials, which acquired the eVent brand in 2017, sold this business unit to Performax Pro, a company based in Hong Kong and founded by eVent managers, including Chad Kelly. “This is a decision we took with Parker a few years ago as we were looking to join a company that shared our vision,” he tells WSA. eVent continues to source its ePTFE from Parker, but the company is now free to investigate other raw materials, including a biosourced polymer it launched in early 2020.
The new reference, eVent Bio, is made from castor bean oil, which, says Mr Kelly, is a non-food crop that does not require much water to grow. The plant-based polymer is blended with nylon, in a solvent- and PFC-free manufacturing process. “It doesn’t compete in the same performance category as ePTFE but offers more stretch and a greener solution, besides opening up space for the brand to grow,” he says. The new bio eVent has a waterproof level of 10K and 10-15K breathability. eVent is also in the final stages of developing a hyper-breathable membrane.
Interest in renewable plant-based biopolymers is growing. German membrane manufacturer Sympatex has just announced a shift to its polyester based membrane which will now include 25% biosourced content, based on Arnitel, made by DSM. In the US, W. L. Gore has partnered with Checkerspot, a biotech company that uses microalgae to make biobased oils. The partnership’s official goal is to develop a biobased DWR, which the industry is in dire need of, but it could also, conceivably, lead to a new biotech waterproof-breathable film.
As new players introduce novel materials, manufacturing methods and end-of-life solutions to provide performance outerwear with a more sustainable profile, the world of waterproof-breathable laminates appears to be changing gears. It is not inconceivable that the established players share a similar outlook.
A new chemistry for DWRs?
UK-based DiOX, a developer of nanoscale silica-dioxide coatings, is preparing to launch a non-PFC durable water repellent (DWR) finish. First developed to provide glass touchscreens and windshields with added strength, scratch resistance and water repellency, the technology could be used to create a water-repellent surface on fabrics, the company says. Its solution does not alter a fabric’s hand feel, as the nanoscale SiO2 bonds to individual filaments. DiOX plans to launch four different finishes for textiles. The range features two hydrophobic formulas, one based on nano silica-dioxide alone, the other combines SiO2 with C6 to offer oleophobic properties. The company claims that this “hybrid” formula uses 50% less C6 than other C6 DWRs. A hydrophilic stain release finish and an antibacterial and antiviral treatment are also in the works.
Dubbed its most innovative and sustainable waterproof-breathable technology to date, Helly Hansen’s Lifa Infinity Pro jacket features a polypropylene film developed by Trenchant Textiles, bonded to a polypropylene face and back fabrics.
