However, in spite of their attempts, the rise of the synthetic fiber industry has not created fibers which excelled their natural counterparts, but rather has created an array of cheap, non-degradable fiber.
Though synthetic fibers may sometimes be capable of handling rough machine washing or be longer lasting than natural fibers, their overall impact is negative on both human health and the environment.
Unlike natural fibers whose production process is clean and simple, synthetic fibers are a result of, well, synthetic processing. In most cases the synthetic materials are pushed through tiny holes, called spinnerets, into the air, forming a super-thin thread. This process is usually referred to as extruding. Once these threads have been made, they are spun, dyed and packed in much the same way as natural yarns. Although certain adjustments have to be made to the process, since synthetic fibers often react differently to spinning and dyeing than natural fibers.
So far, synthetic fibers may not sound too bad. However, the true secret to synthetic fibers lies not in the extruding or post-extruding process, but in what comes before that........
The chemical structure of the Polyacrylonitrile repeat unit
ACRYLIC - From Polyacrylonitrile to Acrylic Fiber
Acrylic fiber is created from a polymer [a synthetic compound consisting of large molecules made up of a linked series of repeated simple monomers (a molecule that may bind chemically or supramolecularly to other molecules)] called Polyacrylonitrile, also known as Creslan 61. The polymer is formed by what's called free-radical polymerization. The polymer is then dissolved in a solvent such as N-dimethylformamide (DMF) which is suspected to cause birth defects. The concern about DMF is significant enough that, in some places, women are banned from working with it.
It is then sent through a multi-hole spinneret and the resulting filaments are coagulated in a water-based solution of DMF. This part of the process is called wet spinning. The resulting fibers are then washed, stretched and crimped . The fiber is then spun and dyed into yarn, thread or may go on to be used in the production of carbon fiber, boat covers, upholstery, etc.
The majority of acrylic fibers are made in the Middle East, India, Mexico and South America. United States acrylic brands include (or at one time included) Acrlian, Creslan, Dralon and Drytex.
POLYESTER - From Poly-mer to Poly-ester
Polyester is made primarily from a synthetic polymer called Purified Terephthalic Acid (or PTA). Though that may sound innocent, PTA is also used in the production of water bottles, capacitors, insulating tape, smoke grenades, etc. A catalyst called Antimony Trioxide, which is suspected to have carcinogenic potential in humans, is added to the PTA.
Then Titanium dioxide is added to dull the color. Other chemicals are then added to allow the fibers to pass through the machinery smoothly.
At this point, it is run through the spinnerets then into cool, dry air. The filaments that emerge from each hole in the spinneret are collected to form small ribbons which are then bathed in spin finish and then coiled in cans. At this point in the process, it is called undrawn TOW.
Ball-and-stick model of a dimethylformamide molecule
Ball-and-stick model of a PTA molecule
The filaments are then run through the draw machine which takes undrawn TOW's from multiple cans and runs them through a hot water trough to raise the polymer temperature. The polymer is then drawn (pulled) 4 times through a steam chamber or a hot water trough. Once the drawing is complete, the filaments are passed through heated cylinders to shrink and strengthen them. The fiber is then passed through a hot water bath and a steam chest to heat it up again. More spin finish is applied and the fiber is run through a drying machine.
The fibers are then cut to the desired length and sent to the spinning mills to be spun, dyed and rolled.
The deeper you dig, the more obvious it becomes that synthetic fibers are truly deserving of their name. They're created from toxic materials, bathed in toxins, heated, stretched, bathed again, on and on until the fiber is workable. Then spun into pretty yarns to be used for new-born baby blankets, adults and kids clothing, toys, etc.
Though each synthetic fiber is slightly different and the process involved in the production of each varies slightly, they all have one thing in common; when all things have been considered, none of them are truly superior to natural fibers.