What are the benefits of TENCEL™?
I’m going to answer this question in two ways. The first builds off of the previous article highlighting the environmental benefits of TENCEL™. The second will focus on its performance benefits.
Now, I’m aware that all new fibers have an environmental impact, and that no production is the best production. That said, when approached holistically, TENCEL™ has a lower environmental impact than many other cellulose-based fibers. In the previous article I noted the toxicity of the viscose process, which TENCEL™ has eliminated. But another important variable to consider is the agricultural process. Many other cellulose fiber sources, including cotton, require significant land area that use water intensive farming practices. Furthermore, non-organic crops are genetically modified and require pesticides and herbicides. Comparatively, TENCEL™ is sourced from fast growing trees like eucalyptus that require no pesticides and up to 95% less water than cotton. This is not to say that other cellulose I fibers like cotton, hemp, linen (flax), and many others are obsolete or unnecessary. In fact, blending fibers together in the knitting process can create very interesting textiles that highlight the best performance features of each fiber and contribute to a better whole.
Environmental standards aside, there would be no point in going to all the trouble of creating a new manufacturing process if the outcome didn’t generate a different, if not superior product. To dig into this, there’s a bit more molecular information to know.
Cellulose is made up of adjacent beta glucose molecules that are alternately rotated 180 degrees in order for their hydroxyl groups to bond. This creates a long, straight chain that is cross-linked to another parallel chain via hydrogen bonds making for a strong bundle called a microfibril. Then microfibrils are grouped together to form a fiber. FYI: Humans don’t possess cellulase, the enzyme necessary to digest beta glucose, which is why we don’t eat trees, grass, etc., so don’t even try.
These linear cellulose chain structures are all oriented “parallel-up” because, well, they grow up, with new sugar residues added to the same end of the growing chain. During the dissolution process, NMMO breaks the hydrogen bonds between cellulose chains that make up microfibrils, but doesn’t disrupt the individual cellulose chains. This allows for the chains to move independently of each other during the spinning process. When the solution is extracted from the spinneret and into the air gap, the cellulose chains are randomly re-aligned in an antiparallel, or head to tail, orientation.
Antiparallel orientation is essential to giving TENCEL™ its unique properties of strength, absorbency, and softness.
Here’s the how and why:
Tensile strength is achieved in TENCEL™ fibers because the antiparallel chains allow for a higher degree of crystallinity, or hydrogen bonding between each other, making them more thermodynamically stable.
The increase in hydrogen bonding between cellulose II chains also increases the number of bonds that can happen when a hydroxyl group meets a water molecule, leading to an overall increase in water absorption. This effect is further amplified from the dense packing and consistent orientation of cellulose chains during the spinning and extrusion process. But wait! there’s more: the spinning and extrusion process also creates a very smooth, round, fiber, giving TENCEL™ its characteristically super soft feel.
Lastly, and possibly most importantly, lyocell is just re-arranged cellulose making it 100% biodegradable.
As bioengineering technology continues to advance, processes and products like TENCEL™ will keep evolving, allowing us to use our scientific understanding of nature to create high performance goods that are not only biodegradable, but have the potential to keep more land undisturbed. This, among other bioengineering research and development of organic sources, is undoubtedly the future of the apparel industry.