Bio-Based Polyester in Kinetic
When we think about sustainable materials, we think about many things including it’s process, energy, water usage and carbon impact - but two are extremely important: 1) How are they sourced and 2) How reusable are they?
Our products are powered by a variety of fibers, each chosen for specific reasons and often combined together to create multiplier effects. We use polyester for many of our products because for a few reasons: Shape resilience (doesn’t shrink), wrinkle-resistance, moisture-wicking abilities, machine-washability.
Polyester has traditionally been derived from crude oil, and to date because of that while it has not been renewably-sourced, it is highly-recyclable.
One of the exciting developments behind the Kinetic fabric (used in our Men’s and Women’s Kinetic products) is that it is made of 15% bio-based polyethylene - or as we commonly know it - polyester.
Our Kinetic products are made from a polyester bi-component fiber that is made of two types of polyester extruded side-by-side together, PET and PTT. Of the total weight, 15% is Bio-based PET.
What is Bio-based Polyester?
It’s just like regular polyester, it’s made of several “ester” building blocks that are polymerized into a chain to create polyester. (See The Fiber Diet) . The esters are basically modified alcohols and can come from any carbon source - to date byproducts of oil-refining have been abundant, but their are alternatives. For bio-based polyester that alcohol can come from a variety of “bio-masses” - but ours come from some of the most common: corn and sugar cane. They’re fast growing, and efficiently convert carbon dioxide, water and sunlight into sugar.
How is Bio-based Polyester made?
Bio-based polyester is made by combining a 4 key processes, many of which we are are all familiar with:
Photosynthesis: Which captures carbon in the form carbon dioxide from the atmosphere and converts it into sugar. In our case this is in the form of corn starch and sugar cane molasses.
Fermentation: Which converts sugar into alcohol - ethanol specifically. So just like brewing, ethanol is created by fermenting molasses with yeasts or bacteria.
Dehydration: This process converts ethanol into ethylene through a reaction that’s byproduct is only water.
Polymerization: The ethylene “monomers” become polyethylene (Polyester or PET) through a polymerization process which joins them together. There you have it - bio-based PET
Here is the process summarized:
Why is Bio-based polyester important?
Bio-based polyester actually captures excess carbon from the atmosphere and converts it into new products - often called carbon sequestration. This is a positive alternative to introducing more carbon into our atmosphere through future oil extraction and hydrocarbon combustion. However, like many agriculture-based solutions, there are other challenges regarding land and water impact and usage. Currently we are using sugar-cane as a feedstock which is rapidly growing - however, lower impact feedstocks are being developed.
When will we transition to 100% Bio-based polyester?
Our partners, such as Toray who makes our Primeflex fabric, are developing better and better processes that maintain the quality, cost and durability of petroleum-based polyester, but in the meantime - though 15% isn’t a 100%, it’s a start. 100% bio-based polyesters will likely arrive on the market in the early 2020s, but until then, we’ll continue to focus on the whole cycle, including our use of recycled polyester such as in our Atlas socks, Responsive T-shirts and 3D-Print-Knit Merino Sweater.