What is polyester?
The Wood Guide · Materials
MaterialWhat is polyester?
The synthetic fibre behind almost every outdoor fabric: parasols, cushion covers and protective covers. What you can expect from it, and where it loses out to the sun.
- Synthetic fibre (PET)
- Absorbs hardly any water
- Fades in the sun
A synthetic fibre that leaves water where it lands
Polyester is not a fabric but a fibre: the raw material from which a canopy, a cushion cover or a protective cover is woven.
Polyester is a synthetic fibre made from oil. Chemically it is polyethylene terephthalate, PET for short, the same plastic as in a PET bottle. It was invented in the early 1940s and has since grown into the most widely used fibre in textiles.
For outdoor items, one property is decisive: the fibre itself absorbs almost no water. A wet parasol or cushion cover therefore dries quickly, and because there is nothing in the fibre that moulds or bacteria can feed on, polyester does not rot the way cotton can.
What you read on a label as "polyester", "PES" or "PET" is therefore the fibre. What the fabric looks like and how long it lasts also depends on how it is woven, dyed and coated.
Dacron is a brand name for polyester. This article is about polyester as a fabric and weave; you can read more about the brand and about cushion filling on our page What is dacron?
- What it is
- synthetic fibre (PET), made from oil
- Moisture absorption
- almost zero, dries quickly
- Mould
- the fibre does not rot; mould only grows on dirt on the fabric
- Strength
- tear-resistant, stretches little
- Sun
- the colour fades, the fibre weakens slowly
- Waterproof?
- only with a coating on the fabric
- Where you see it
- parasols, cushion covers, protective covers
To be honest, polyester is not a miracle fibre for outdoors. Without treatment the fabric lets water through after a while, a bright colour fades in full sun, and washing releases microfibres into the waste water.
What polyester can do, and what it cannot
A short list of the properties that matter for fabric that hangs or lies outdoors.
| Property | What it means | What you notice |
|---|---|---|
| Absorbs little water | the fibre is water-repellent in itself | the fabric dries quickly after a shower |
| Strong and tear-resistant | long, drawn plastic fibres | the fabric can take being under tension, like a stretched parasol |
| Dimensionally stable | stretches and shrinks little | the fabric keeps its shape, even after getting wet |
| Takes colour well | the fibre takes up dye at high temperature | many colours, including dark ones |
| Sun | UV light slowly breaks down dye and fibre | a bright colour fades after a few summers |
| Heat | plastic: melts at high temperature | a spark or hot ash can melt a small hole in the fabric |
| Low maintenance | dirt tends to stay on the surface | a damp cloth and mild soap are often enough |
How polyester fabric is made
From the fibre itself to the finished fabric there are four steps. The last one determines most of all whether a fabric really keeps water out when used outdoors.
- Spinning the fibreMolten PET is forced through fine holes to form long filaments, which are then stretched. That spinning and drawing gives the fibre its strength. You can read more about that process on the dacron page.
- Weaving yarnThe filaments are twisted into yarn and woven crosswise. The thicker the yarn and the tighter the weave, the sturdier and denser the fabric.
- DyeingPolyester is dyed at high temperature. Sometimes the colour is already in the molten mass before spinning: then it runs through the whole fibre and fades more slowly than dye on the surface.
- Coating and finishingFor outdoor use the fabric often gets a thin layer on the back or a water-repellent treatment. That is what makes it waterproof or water-repellent, not the fibre itself.
A water-repellent fabric makes light rain bead off. A waterproof fabric has a closed coating. Such a layer wears down over the years through sun, folding and rubbing, and then water slowly gets through after all.
Parasols, cushions and covers
Parasols
The canopy of a parasol is almost always polyester. It has to be light, able to be stretched taut and quick to dry after rain. According to its product page, the Marbella parasol below has a polyester canopy on an aluminium frame.
Cushions
Outdoor cushion covers are usually polyester. They dry quickly, and the fibre itself does not go mouldy, although a green film can form on the surface if a cushion is left in the rain for weeks. The filling is a separate story.
Covers
Protective covers for garden furniture often consist of polyester with a plastic layer. According to the product page, our protective covers for picnic tables are made of PVC and polyester.
What sun, rain and mould do to it
Sun
Sunlight breaks down the dye first and only much later the fibre. A dark or brightly coloured fabric facing full south therefore fades sooner than a light shade. Fabric with colour through the whole fibre generally keeps its colour longer.
Rain
The fibre itself absorbs no water, but whether the fabric really stays watertight depends on the coating and the weave. In prolonged heavy rain any fabric can let water through.
Mould
The fibre is not food for moulds. A fabric stored wet can still go mouldy or get stains, because dirt and dust on the surface do provide a breeding ground.
Wind and heat
Strong polyester does not tear easily, but a parasol under tension in a storm is always a risk for the frame. Closing it in strong wind is the rule. Fire and sparks do not belong near a plastic fabric.
Pros and cons of polyester outdoors
What it does well
- Dries quickly, absorbs hardly any water
- Does not rot or go mouldy by itself
- Strong and dimensionally stable
- Many colours and easy to process
- Little maintenance needed
Where it falls short
- Fades in full sun
- Waterproof only with a coating, and that wears down
- Melts with sparks and heat
- Plastic from oil, slow to break down
- Microfibres are released when washing
Every time a polyester item is washed, tiny fibres are released that end up in watercourses via the waste water. The fibre breaks down very slowly in nature. That is a known drawback of all synthetic textiles, and no reason to wash your parasol canopy more often than necessary.
Cleaning and storing polyester
- Brush it dryFirst sweep away dust and leaves with a soft brush, before they stick to the fabric with moisture.
- Lukewarm water and mild soapUse a damp cloth and a mild cleaning agent. Avoid harsh cleaning products; this is also stated for our parasol. Bleach is not part of it.
- Let it dry thoroughlyLet the fabric air-dry, without hot air or a tumble dryer. Only store it once it is completely dry, otherwise stains appear.
- Protect it in bad weatherClose the parasol in strong wind and protect it in prolonged rain, for example with a protective cover. That spares the coating and the fabric.
Frequently asked questions about polyester
Is polyester the same as dacron?
Dacron is a brand name for polyester, so chemically it is the same fibre. You can read more about the brand and about cushion filling on our page What is dacron?
Is polyester waterproof?
The fibre itself absorbs hardly any water, but a fabric is not automatically waterproof. That comes down to the weave and above all to a coating on the fabric. With water-repellent fabric, light showers bead off; in prolonged heavy rain, water can still get through.
Does polyester fade in the sun?
Yes, over time. Sunlight attacks the dye first. Dark or bright colours facing full south fade faster than light shades, and fabric whose colour runs through the whole fibre usually lasts longer.
Can polyester go mouldy?
Not the fibre itself: there is nothing in it for mould to feed on. But mould can grow on dirt and dust lying on the fabric, especially if you store it wet. So dry it well and clean it now and then.
How do I clean a polyester parasol canopy?
With a soft brush, a damp cloth and a mild cleaning agent. Do not use harsh cleaning products or bleach, and let the fabric air-dry.
Is polyester bad for the environment?
It is a plastic made from oil that breaks down very slowly in nature, and washing releases microfibres. On the other hand, a fabric that lasts for years needs replacing less often. Both the advantages and the disadvantages are real.
A parasol or cover for outdoors?
Take a look at our parasols and protective covers, or read on about the fibre behind the brand dacron.
Have a question about your project? Just ask — we're happy to help.