Marketed in the 1970s as “a miracle fibre that can be worn for 68 days straight without ironing, and still look presentable,” polyester does have a number of good performance qualities:
Durability - polyester is a high-strength material that can withstand regular wear and washes. It also shows excellent resistance to wear and abrasion, which is why sportswear is usually made of polyester.
Versatile - polyester can be easily blended with other fibres (in particular cotton) to combine its benefits with those of other fibres and achieve even better end products.
Dry-wicking fabric - polyester also absorbs moisture well, but instead of retaining it, it evaporates quickly, leaving your garment dry (another reason why it’s preferred for sportswear).
Wrinkle and shrinking resistant - polyester will hold its shape and form, and also resists wrinkles and fades, no matter how many times it's washed.
Easy care - polyester clothes are 100% machine washable and dryable, don’t require much ironing, and can dry-cleaned.
Less prone to stains - as polyester is less absorbent, it also doesn’t stain easily.
Incredibly lightweight - another reason. why it’s used for activewear.
Consistent cost - as it's synthetic/man-made, it doesn’t suffer the same market fluctuations that natural fibres like cotton do, resulting in more consistent costs.
It also has some (limited) environmental positives:
Recyclable fabric - polyester is 100% recyclable at the end of its life, either mechanically or chemically, providing a use for one of our biggest waste streams and diverting plastic from our landfills. However, the recycled fibre usually degrades every time it gets recycled, while most recycled polyester textile (in particular rPet) is made from recycled plastic bottles, rather than polyester clothes.
Water friendly - polyester production uses less water than some natural fibre materials, although that is relative – it does still need water (see below).
Polyester production methods have huge environmental impacts:
Non-biodegradable - as a plastic, polyester is non-biodegradable. Whether it's new or recycled, it takes years to disappear once thrown away, contributing to a staggering 8 million tonnes of plastic entering the ocean every year.
Derived from oil - polyester is derived from petroleum, and the transformation of crude oil into petrochemicals releases dangerous toxins into the atmosphere.
Microplastics - plastic clothing is the number one cause of plastic microfibres in our oceans. Up to 700,000 individual fibres can come off our clothes in an individual wash cycle, releasing billions of microfibres into our waterways and oceans and then into our food chain. Again, that’s the case whether the polyester is new or recycled.
Limited recyclability - polyester may be recyclable, but that's mostly only downwards into materials of ever-worsening quality, and only for a few times before the fibre loses its quality. That’s why most recycled polyester fabric comes from plastic bottles, rather than existing polyester garments or textile.
Energy intensive - producing polyester requires a lot of both heat and cooling, emitting greenhouse gases into the environment. And while recycling PET does save energy and emissions over new polyester, it's still more energy intensive than using organically produced natural fibres.
Needs toxic dyes - colouring polyester requires dyes, known as disperse dyes, that are insoluble in water and, like polyester, don't readily decompose. Waste water from textile factories containing leftover dye is difficult to treat, so it enters the environment, where its toxicity causes serious problems to plant and animal life, as well as to humans.
It also has certain performance limitations:
Less breathable - the fact that polyester is a plastic-based fabric means it has limited breathability, making it unsuitable for things like bedding.
Temperature-sensitive and moderately flammable - polyester may not be highly flammable, but it can catch fire - and if it does, it tends to stick to skin and leaves more severe burns than natural fibres.
Lacks a soft texture - unlike cotton, which feels soft against your skin, polyester has a slightly rough texture and might not feel comfortable against your skin.