Due to the vegan movement, the use of leather in fashion is coming under increasing criticism. In recent years, numerous alternatives have therefore come onto the market. But can they really replace leather? The German research institute FILK (Forschungsinstitut für Leder und Kunststoffbahnen) Freiberg Institute GmbH has examined various leather alternatives in a study. Research director and managing director Dr. Michael Meyer, explains the results and the resulting questions.
What exactly does FILK do?
The FILK was founded 120 years ago. Our focus is research and development of polymers. This involves flexible materials that are made up of several layers of polymers, such as conveyor belts, products from the medical sector or materials used in public transport. Leather and artificial leather are also part of this, but are rather a small part of our research. It is important to mention that we are independent. We take up questions that develop in industry or are brought to us. Sometimes we also look for questions ourselves that are important in this material segment. This is how the study on leather and artificial leather came about.
The study was done on your own initiative?
Exactly. We have a large test laboratory and as a scientist you eventually become curious about the technical performance of these different artificial leather materials. It was important to us that the materials were suitable for industrial use, i.e., that they were already in use.
How many artificial leather materials did you test in the study?
Around 20, to name a few: Pinatex, Cork, MuSkin, Wood-Textile, Kombucha, Deserto, Vegea, Teak Leaf, SnapPap. All of them are already on the market and have been compared by us according to set standards.
All these materials are completely different in structure and properties. That was a real challenge. As a comparison material, we compared leather and the standard artificial leather with the still quite new materials made of cork, fungus, bacteria, cellulose, etc., which have a completely different structure. There is also the question of which property the user is most interested in or a seller wants to advertise in the end: durability, water resistance...?
At the moment, there is an incredible buzz about MuSkin, i.e., artificial leather based on mushrooms. Stella McCartney has already used it in her collections.
With mushrooms–as far as they are cultivated–the big challenge is to create any mechanical stability at all. As a design element it may work well, but we were not concerned with design, but with technical quality. Of course, you can add a coating, but then a cotton backing would be much more stable, as in the case of normal artificial leather, for example. With real leather, the stability is provided solely by the grown structure of the skin.
The coating is often seen as a problem because it is mostly fossil-based. With Pinatex, the leather alternative made from pineapple and research is being done on a plastic-free coating.
Pinatex is an exciting material. That is indisputable. I would describe it as a nonwoven based on cellulose fibers with a binder. The question here is again: What is important to the consumer? A nice surface that also feels good, or a soft structure? In my eyes, Pinatex is not comparable to leather. For me, it is a material in its own right, but not really a leather alternative.
Let's take the normal artificial leather with PVC or polyurethane. That usually looks nice. Is it comparable to leather?
Not in terms of longevity. But of course we have to talk about time scales. If you assume a use of ten to 15 years, as in the automotive sector, then real leather is the most stable. But we hardly ever use shoes for that long. Shoes made of artificial leather are quite stable, but you sweat in them because they don't let water vapor through. Many people are working on this, but so far they have not succeeded in improving it. But does it even matter? What do consumers want? Wearing comfort, design, do they want to use animal materials or not?
No, leather scored best across the board. Water vapor permeability in leather is good, but not outstanding. This is really excellent in a mushroom material, for example. But I can't make a shoe with only water vapor permeability. I also need a certain stability. Resistance to tearing is equally good with leather and synthetic leather, but with synthetic leather the water vapor permeability is poor because it is a synthetic material. With MuSkin the stability is bad, with cork I get stability exclusively from the support... The message of the study is: for technical use, leather shows the most comprehensive behavior for universal criteria, i.e. the best values for most parameters.
This result will not please vegans. Another problem is that most leather alternatives are coated with plastic. Is there any progress in replacing this fossil layer with an ecological coating?
There are various research projects on this. Especially with vegetable oils. But they don't yet do what we want and they are much more expensive. But we are confident that this will work in a few years. But even then, a fossil polymer will only be replaced by one made from renewable raw materials.
Would this renewable polymer be degradable?
You can't give a blanket answer to that. There is now a green vinyl, i.e. PVC made with renewable raw materials. This has only been on the market for a short time and is not biodegradable. And there are polymers that are fossil and can be biodegraded. That can be adjusted. But when you choose between "fossil" and "renewable,” you start a whole other discussion: If you use vegetable oil, then you could make food out of it. Or make a fuel. If I use soya oil, for example, then it is produced on arable land on which I could also plant food. Or let's take wheat or maize starch. Wouldn't it be better to use these raw materials for food and nutrition instead of leather alternatives?
Leather tanned with chrome is degradable. But a proportion remains and that is of course harmful to the environment. But this argumentation leads in the wrong direction, because shoes, no matter whether they are made of leather or fossil materials, do not end up on the compost heap at the end of their life cycle, but are burned. In the process, the chrome is completely incorporated into the slag.
Nevertheless, the use of chrome is one of the strongest arguments of the anti-leather lobby. Leather in itself is a waste product of the meat industry. But in many developing countries, tanning and dyeing is very polluting.
That is important for me to mention: No animal is bred to make leather. But still 80% of leather is tanned with chrome. But again, you can make a process good or bad. Even with artificial leather from China, a lot of harmful solvents are still used, which are no longer used in Europe. We have very high standards in the EU as far as tanning is concerned. If a company adheres to them, as is the case in Germany, there is hardly any criticism to be made.
Are there already alternatives to chrome tanning?
Do you want to hear our dreams or what already exists in reality? Rhubarb is a niche because there are simply far too few of the roots. The development of tanning with privet is quite far. There are kilometers and kilometers of this hedge plant. Research with olive leaves is also well advanced. This is the utilization of a by-product that would otherwise be dumped or burned. But all these processes are more complex and take much longer. The vision of the future is to produce tanning agents from biotechnological processes. But that is still a long way off.
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