Polyurethane grades from the softest of foam to the most indestructible of thermoplastics drive innovation and production in the footwear industry. Jane Denny reports.
Polyurethanes drive innovation in the global footwear business
About 13bn pairs of shoes and boots were made in China in 2014, which is equivalent to 60% of total production, according to footwear machinery maker DESMA’s ceo Christian Decker.
Decker’s aim is to replace labour intense production lines with footwear production automation.
Decker said: “A shoe that can be produced by one person in 12 seconds in Europe may take 22 seconds in China with 15 people working around the machine, each with a specific function.”
Desma’s research indicates that by now, average global consumption is around 2.5 pairs/person/year.
Sport shoes are the dominant market, with Nike and Adidas the key players. In 2014, Adidas announced sales of $14.5bn. Rival Nike reported revenues of $27.8bn, up 10% on 2013 and double what it was in 2005.
Relative newcomers to the industry, Skechers’, founded in 1992, posted 2014 revenues of 2.3bn, up around half a billion on 2013 revenue.
The sports shoe market pivots on bounce, comfort and support, which explains the popularity of differing grades of polyurethane in footwear design. Daewoo created the material for the iconic baseball training shoe, the Nike Foamposite One launched in the late 1990s.
Today, it is rare for an athletic shoe to not contain PU foam in at least some of its composition. According to John Zhang, head of Bayer MaterialScience’s (BMS) global footwear competence centre in Shanghai, around 500kT of PU is used in sole making worldwide yearly.
Zhang added: “Polyurethane is ideally suited for shoes due to its extreme durability and the theoretically unlimited design freedom it offers.”
The use of polyurethane signified a radical change for an industry that had relied on traditional materials such as leather and rubber.
The move away from those traditional materials meant customers were no longer restricted to the black, brown and white colouring possible from leather raw materials. It also meant they could choose footwear with more or less resilience, softer or harder support elements, alongside a range of other variables.
Footwear technology drives innovation
In the same way that viscoelastic foam revolutionised the bedding industry, memory foam for insoles is proving a game-changer for sections of the footwear industry. Following the foam’s introduction into Skecher’s ranges, the company saw sales increase by 28% from $1.84bn in 2013 to $2.38bn in 2014. According to its financial filings, profits rose well over double at $209m for 2014 compared to $94m the year before.
Now, the manufacturer has introduced the technology across its ranges and it is included “in everything from cozy winter casuals to next spring’s sandal,” from children’s to adult shoe collections, as indicated in the company’s marketing material.
In another innovation, Nike launched its Flyknit range in 2012. The shoe features an upper made of one knitted piece, compared to several pieces stitched together as in traditional athletic shoemaking.
Melted into the knit yarn is paper-thin layer of polyurethane material that keeps the upper dry. This innovative process has proven sustainability advantage, reducing waste of the Nike Flyknit Lunar1+ upper 80% compared to traditional Nike running footwear production processes.
Shoe production technique and process
The amount of time it takes for a shoe to reach the shop floor after conception can vary considerably. Footwear industry association SATRA estimates that the window of time from the original design concept to shop delivery, at least for some fashion footwear, can be as short as ten days.
For long-running product lines, for example sports shoes, it could be up to 15 weeks – including testing, engineering, pathfinders and extensive tooling up, according to SATRA research.
At present, the majority of these shoes will use plastics and rubber materials and they will come from China. Here, shoe production is labour-intensive. Production lines can be 300m long with staff carrying out simple repetitive tasks at workstations.
Mass customisation, individualism and 3-D print
Meghan Cleary is a shoe expert and blogger of ShoeAreYou? based in Los Angeles, US. Cleary said: “Currently, there is a trend towards customisation in the shoe industry.”
“Consumers are starting to clamour for them and retailers are starting to tune in. They are realising that they can get extra market share from this type of initiative.”
“Everyone wants to feel like they their shoes are something special to them. It’s a way of distinguishing yourself,” she said.
One example of this is Shoes of Prey. This is a New South Wales, Australia-registered internet supplier of conventional footwear supplier, although the company does not explicitly use polyurethane in its designs it allows customers to design their own shoes.
Highlighting the company’s partnership with key US department store Nordstrom, Cleary said customisation was emerging an important factor for brand growth. Fashion retailer Nordstrom said it would have six design your own shoes studios in malls across the US by spring 2015.
The service, which ceo and co-founder Michael Fox said offers over 70 trillion combinations, is a follow-through from Nike ID – the sportswear makers online customisation-service.
Fox said it “fulfils a current demand where customers are looking to participate in the design process to get exactly what they want.”
“Together, we see customisation and manufacturing on demand as the future of retail," he added.
Now customers are able to use the brand's 3-D designer in-store, with access to swatches of over 170 materials. Shoe stylists offer guidance and, after completion, the designs are hand-made at Shoes of Prey’s factory in Southeast Asia and delivered in less than four weeks.
In December 2014, the company announced plans to build another factory, five times bigger than the first.
Shoes of Prey’s philosophy is supported by US-based management consultancy Bain & Company, which said: “By providing customisation options, brands raise loyalty at a time when it’s more important than ever.
“A recent Bain survey of more than 1,200 global executives across a range of industries, 67% believe their customers are becoming less loyal to their brand.
“Equally, customisation helps companies differentiate their products from those of their competitors at a time when the internet is rapidly creating high price transparency and making it easier for customers to compare products with standard features,” according to Bain & Company.
Print your own shoes
Polyurethane is playing an important role in the niche world of for 3-D printed shoes, Cleary said this niche is today’s most exciting thing. She highlighted the design innovation of US firm United Nude. One of this firm's 3d printed offerings appears on the cover of Urethanes Technology International's June/July issue.
United Nude teamed up with three architects, Zaha Hadid, Ben van Berkel and Fernando Romero and two designers Ross Lovegrove and Michael Young, to create pairs of shoes using 3D printing. Each pair was created using two different materials: the soles were printed in polyamide, while the uppers were formed from thermoplastic polyurethane (TPU), which is softer and more flexible.
United Nude also has a version of a 3d printed shoe which can be produced at home on a desktop 3d printer, but it is not clear if the design would be practical with polyurethane.
Cleary said “Across 3-D print, the shoes themselves are still quite basic. We are just at the very beginning of it but it will be interesting to see where it goes.”
For Cleary it’s an interesting proposition, Cleary said, and one that may become even more so if a 3-D print facility becomes a feature of every high street and retail hub. A major advantage is the elimination of scraps and waste in the process, as the process only prints the shoe components that are needed, said Beard.
Custom cobbler, as start-up company Feetz describes itself, “offers 7bn sizes, one for everyone in the world,” according to its marketing material.
Founder Lucy Beard was frustrated by not being able to find the right size and style shoe to buy. Baffled by the absurdity of Starbucks ability to offer over 87,000 customised combinations of its products against footwear’s scarcity of variation, Beard came up with her idea and launched in 2013.
3d print PU
Michigan-based APS Elastomers has launched thermoplastic polyurethanes (TPUs) for use in 3-D printing.
The technology allows pellets to be placed directly into the printer, which APS says is a more cost-effective alternative to filament spools.
The firm’s material Zythane offers “durability, toughness, chemical resistance, flexibility and processing ease” said APS. “This is an exciting time for smaller manufacturers and moulders”, said Stephane Morin, principal at APS Elastomers,
He said: “While we are capable of delivering truckload quantities, our business model has been to support small to medium-sized customers by distributing thermoplastic elastomers with no minimum order quantity
“No other producer of TPEs offer low volume orders with the high level of service we provide.”