The fight for durability
A “radical step forward” in making its footwear more durable helped Keen win recognition in Time’s ‘Best Inventions’ list at the end of 2024.
Asoling innovation has helped outdoor footwear brand Keen win recognition from Time magazine. The brand’s Targhee IV hiking boot was one of the products that the magazine listed among the ‘Best Inventions’ of 2024. Following this recognition and what Keen has called an “initially limited debut” last year, the boot is back as part of the company’s spring-summer 2025 collection.
Features that enhance the durability of the Targhee IV are what captured the attention of its evaluation team. “A hiking boot breaks down when dirt, mud and water cause the midsole to become unglued from the outsole,” the magazine summarised. “This is called delamination, and delamination is the enemy of durability.”
The use of a recently launched, proprietary technology called Keen Fusion in the construction of the Targhee IV is at the core of the footwear brand’s response to this age-old problem. This technology re-engineers the way the outsole, midsole and upper are joined together. Fusion works by using heat, pressure and high levels of automation to inject a liquid polyurethane into the space between the upper and the outsole. The liquid solidifies in seconds and forms the midsole of each boot. It also forms bonds that are three times stronger than those on offer from glue. Injecting the midsole between the upper and the outsole fuses the whole shoe together. “I’m thrilled to see our Targhee IV come to life,” says the brand’s senior vice-president for product, Scott Labbe. He describes the product as “a radical boot” and as “footwear that is no longer limited by weak bonds and short-term fixes”. He says this is a testament to the company’s commitment to reducing the impact of its shoes.
Testing has proved the Targhee IV’s robustness. In in-house lab tests, the boot did not break down after 1,600 kilometres of use. It also stood up to all attempts on the lab’s ‘pull machine’ to force the components of the boot apart.
Unstuck in the mud
Delamination occurs when the adhesive that is usually used to attach the outsole to the rest of the shoe begins to degrade. When this happens, the sole starts to peel away, making the footwear unwearable. Repairs are often possible but will only last as long as it takes for delamination to strike again. And the unsticking can occur at the least convenient moment. At some point, most hikers will have come across the detached, abandoned sole of a fellow-walker’s boot in the mud or by the side of the trail.
In the face of this, Fusion is “a radical step forward”, Keen insists. Fusing the sole and upper of the boot together using the midsole as a lasting bonding mechanism constitutes an innovative direct-injection process, the company claims. As well as enhancing durability, this eliminates the need for solvents, it says, taking “toxic glues” out of the equation. The midsole still works as a midsole too, of course, providing supportive cushioning and high levels of shock-absorption “adventure after adventure”, the company states.
Performance-enhancing lugs
Other features that enhance the Targhee IV’s sustainability story include leather sourced from tanneries certified by multi-stakeholder body the Leather Working Group (LWG). Certified tanneries must meet the LWG’s requirements in areas such as reducing their consumption of energy, chemicals and water. The boots are built for long-lasting performance and comfort, Keen says. The outsole that Fusion fuses to the rest of the boot is also proprietary, from the brand’s Rugged range, with hard-wearing multi-directional lugs that offer good traction on “even the harshest of terrains”. The brand describes the material it has used in this outsole as being twice as durable as rubber.
The product also features a removable, air-injected insole from the company’s Luftcell range. The fibres in the laces are recycled and moisture protection comes from the Keen Dry breathable waterproof membrane and a proprietary, PFAS-free durable water repellency finish. There is also odour protection from proprietary technology that is free from pesticides and harmful chemicals.
Sustainability is an important part of Keen’s push forward with Fusion, too. It has the machinery in place in its own facilities in Thailand and the US to put the new process into practice and this has allowed it to collect important data. From this, it now knows that footwear construction with Fusion consumes 3.5 times less electricity per pair than the process with traditional cement construction. Using less energy and no solvents has led the company to calculate that the carbon footprint of a pair of boots made with Fusion is 1 kilogramme of CO2-equivalent lower than the figure for non-Fusion footwear.
“Durability is sustainability, and so is reducing the use of energy and solvents,” Keen concludes. “We are on a mission to make the world’s cleanest, longest-lasting shoes. We call this ‘Consciously Created’, and Fusion is a big step forward on our journey.” There is more to come.
The rough and tumble of the trail can accelerate delamination of cemented soles on footwear. Keen claims its innovative direct-injection process, Fusion, is three times stronger than adhesive.
All credits: Keen
