Searching for durable materials in the future of the leather industry

In the tumult of a tanning drum, only the strong survive. Akin to a large washing machine, the drum creates a roiling environment where liquids can permeate otherwise resistant materials. There, fat liquors and colorful dyes can flow into tough animal hides, helping to transform the material into an icon of luxury. It’s there in the churn of the drum that leather is born. 

Strength is a foundational quality in leather. The material’s durability is what allows it to be used in the interior of cars, to style outfits and to protect motorcyclists from harm (among many other uses). Its strength also allows it to endure the tanning drum, where tanners imbue the material with its characteristic color and hone its softness. This unique blend of artisanal beauty and an underlying, rugged strength has made leather into a timeless material. 

Yet, it is also a material under pressure by an ever more crowded market, one in which plastics have risen to prominence. Along with an increasing global demand for sustainable materials, competition from low-cost plastics has left leather manufacturers struggling to innovate the leather making process while also preserving their ancient artform. 

In the materials space, durability is a catchall term that can mean many different things.

“When we think about the durability of materials, usually we're talking about how long the product lasts in the consumer's hands,” explains Nick Yaraghi, the Director of Product Development for Finishing at Modern Meadow. Yaraghi is an expert in materials engineering and has spent nearly a decade at the company thinking about product durability. 

“But from an engineering standpoint, there’s many ways to measure durability,” he explained. 

In the technical weeds, durability can be described according to its [Botta V. ECOS -Environmental Coalition on Standards Deep Dive: Standards to Measure Textile Durability. Environmental Coalition on Standards; 2022.]:

• Structural (mechanical) durability: ability to stretch without breaking, flex without cracking and resist tearing or puncture.
• Cosmetic durability: resistance to scratches, staining/soiling, color fading (color fastness) and pilling behavior.
• Environmental durability: ability to resist breaking down in the presence of environmental stressors, such as heat, moisture, UV light and chemicals (think body heat, sun exposure, sweat and detergents).
• Lifetime durability: retention of value to the end user through consistent appearance and utility.

Which aspect of durability is most important depends on the context of how a product will be used. Leather gloves, for example, may sacrifice mechanical strength to become lightweight and comfortable, but will have to prioritize cosmetic and environmental durability. A leather apron used by metal workers, on the other hand, will need to prioritize structural and environmental durability to provide maximal protection. 

“For tanners, mechanical durability is particularly important in a raw material, because it has to survive the drum,” emphasized Yaraghi. 

INNOVERA^TM is designed to be drop-in ready, meaning it can be processed by tanneries using the same infrastructure and workflows that are used with traditional hides. Specifically, INNOVERA^TM is designed to drop in to the final stages of the tanning process, where the drum is typically used to give hides deep coloration, softness and fullness. 

In the retanning step, the material is tumbled, along with water and various dyes and chemistries, in what resembles a large washing machine and needs to withstand repeated impacts and flexing. Materials that survive this step need to then withstand subsequent mechanical stress during post-processing steps such as milling, staking and buffing, where the material is further tumbled, vibrated and sanded. 

The retanning and subsequent post-processing steps are key determining factors in leather’s final properties, from color to softness to lifetime. So, the material needs to survive all these steps to see the benefits. To fulfill tanner needs, then, as well as those of the final user, INNOVERA^TM’s durability must be designed at a molecular level. 

“A lot of our durability comes from the very deliberate engineering of the material to closely mimic the structure and chemical nature of leather,” adds Yaraghi. “Leather is essentially a fiber-reinforced composite material—its got this hierarchical structure of collagen fiber bundles, which get thicker (but less dense) as you go deeper into the skin.” 

According to Yaraghi, that gradation is what gives hides and leather much of their performance. “We engineered INNOVERA^TM to have a similar kind of fiber structure, with interlocking fiber bundles that give it strength. And, we use our Bio-Alloy^TM—a miscible blend of biopolymers—to coat this structure and provide all the functionality needed for tanning chemistry to interact with the material.” 

Figure 1: Engineered For Endurance. Cross section of INNOVERA^TM following 100K Bally Flex cycles. Upper portion of the material speaks to the material’s excellent adhesion testing results by showing no sign of surface finish disbonding. Similarly, the interior structure of appears unchanged with no signs of deformation despite 100,000 rounds of flexing. 

Together, INNOVERA^TM’s mixture of nylon (formed from recycled car tires), soy-based plant proteins and biopolymers create a uniquely long-lasting bio-renewable material. “A lot of other next-gen materials, like mycelium, rely solely on the strength of biological materials (polysaccharides, proteins), which makes it really challenging to produce a truly durable product.” 

Yaraghi explains that “by using both plant proteins, nylon, and Bio-Alloy™, INNOVERA^TM is not only able to survive the retanning process, but it can uptake the chemicals that give you that warmth, softness and fullness that you expect from leather.”

The result of this engineering is clear in the wide range of tests that can help assess long-term performance. “The Bally Flex test is a common one to assess structural durability,” Yaraghi explained. “You basically subject the material to repeated, cyclical rounds of flexing. A common industry standard for leather is to run 100,000 cycles and then check to make sure there aren't any failures in the material, such as cracking.”

To this end, INNOVERA^TM has proven durable, showing no structural defects after 100,000 cycles. Table 1 shows the results of several durability tests and how INNOVERA^TM compares to industry standards. Notably, INNOVERA^TM’s performance validation shows it’s 2x stronger than the reference leather, demonstrating nearly double the tensile strength standard, elongation potential and tongue tear resistance as compared to the leather. 

As a next-generation material, INNOVERA^TM has the potential to unlock new possibilities for the leather industry, in part due to its advanced durability. 

“When you have strength that is substantially higher than traditional leather, you can do some really interesting things,” Yaraghi mused. “For example, you can split the material to half the thickness and still maintain the strength you would need for some end applications.” 

The thinner you go with leather, the weaker it gets. This is a problem because product designers have to balance the desire for lightweight, soft and drapeable materials and the need for strength. Gloves are a good example: you want a thin material to improve tactile capabilities, but you still need a tear- and abrasion-resistant material to protect the hands. Yaraghi suggests that “with our material, we've seen that you're able to split it and go a lot thinner than you could with leather while still maintaining the strength that you would need.” 

Having the ability to reduce weight while maintaining a high level of strength can be particularly important in the transportation industry, where reducing vehicle weight translates to better fuel economy.

Improving durability is also an important aspect to material sustainability. INNOVERA^TM is designed to be sustainable from its inception, being made from 80% renewable carbon content and capable of a circular lifecycle. But its durability also means that products may last longer in consumer hands, further reducing waste accumulation. 

Modern Meadow is committed to supporting the leather industry with performance material sourcing. INNOVERA^TM is not only designed for durability and sustainability but is engineered to be scalable to meet the needs of a global market, with a production capacity of 500,000 m²/year.

Even without a clear definition of durability, you’ll recognize it when you see it, when you feel it.  INNOVERA^TM is designed to be easily recognized as durable, both for tanners and end users. As Yaraghi describes it, “INNOVERA^TM really brings together science and nature at a molecular level, giving you the beauty of leather and the performance of modern materials science.” 

It’s a material designed to help carry on the enduring legacy of the leather industry. Not only does it blend science and nature, but it empowers craftsman tanners to bring the time-honed skill of leather making to bear on a cutting-edge canvas. That blending of worlds is why our tagline is 'harmony in your hands'.