Recycling is hard. Sorting, cleaning and transporting cost energy; but we need to do it. Anything we can re-use, re-purpose or repair is key to solving the multitude of problems we face. Numerous and uniform, plastic bottles made from polyethylene terephthalate are the beginning of the recycle and repurpose revolution.
The conversion of PET bottles into yarns for textile manufacturing is at the forefront of polymer recycling. Via an ultra-high-efficiency process train pioneered in Germany (global leader in PET bottle recycling), PET bottles can be spun into high-quality polyester or recycled PET (rPET) fibres at a material efficiency of 96% (i.e. only 4% of material is lost throughout).
The process is ingenious and fascinating. PET bottles are first sorted by colour and material via colour recognition tech like pulsed laser spectroscopy. They are then shredded into pellets and broken down into their molecular building blocks (depolymerised) using ethylene glycol as a solvent. After filtration, the monomers are re-polymerised at around 180ºC, spun into fibres and woven into fabric.
Comparative life cycle analysis of PET recycling compared to cotton farming and processing has shown that while it takes about 40% less energy to grow and make cotton fibres, cotton growing requires vastly larger amounts of water than the rPET process (amounts vary from 7,000 to 29,000 litres of fresh water per kilo of raw cotton fibre). Pesticides and fertilisers used in traditional cotton cultivation also have ecotoxic effects in contrast to organic cotton cultivation, which can be avoided when recycling.
In addition, the higher durability of rPET fabrics makes them longer lasting, reducing clothing waste dramatically. The PET recycling process has become so refined that rPET fibres have been shown to outperform cotton and non-recycled PET (vPET) fabrics in several ways. First, rPET fabrics are twice as air permeable or breathable as cotton or other vPET fabrics. Cotton fibres tend to be quite ‘fuzzy’ when looked at under the microscope. rPET fibres, on the other hand, are incredibly uniform in thickness, allowing air to flow in between them. Because of its chemical structure, PET is fundamentally hydrophobic (not fond of water). So compared to hydrophilic (water loving) cotton, PET fibres are much better at transporting sweat away from the skin-fabric interface and increasing wearability and comfort. rPET fibres can also sustain much higher axial loads than cotton (2.1 MPa versus 1.2 MPa) before ripping while retaining their elastic properties. rPET fibres can reversibly deform to 39% of their original length, cotton only 7%, making them particularly comfortable to wear.
This all makes rPET fabrics the ideal building blocks for the high-performance athletic wear we create at OHMME. And, of course, for a better future.
T Sharabaty a, F Biguenet, D Dupuis & P Viallier. “Investigation on moisture transport through polyester/cotton fabrics”: http://nopr.niscair.res.in/handle/123456789/2603
Telli, Abdurrahman, and Nilgün Özdil. “Effect of Recycled PET Fibers on the Performance Properties of Knitted Fabrics.” Journal of Engineered Fibers and Fabrics, (2015).
Shen L, et al. Open-loop recycling: A LCA case study of PET bottle-to-fiber recycling. Resour Conserv Recy(2010)