PolyEthylenTerephthalat

We wanted to write something about PET-bottles because they are an everyday object that deserves to get more attention from the public. The effects it has on our environment are considerable but even more remarkable are the great efforts that are put into the recycling and waste management of PET.

Zahlen und Fakten

In der Schweiz sind pro Jahr 1.5 Milliarden PET-Flaschen im Umlauf. Das entspricht 45’267 Tonnen PET. Von diesen Tonnen werden 83% recycelt. Um diese alle recyceln zu können, muss man überall PET Sammelstellen aufstellen. In der Schweiz haben wir 9000 Standorte an denen man PET entsorgen kann. Zudem gibt es auch noch viele Betriebe, die auch PET Abfälle sammeln. Insgesamt sind das über 36’000 Betriebe und sammeln zusammen 2/3 der recycelten PET Abfälle. Um dies zu fördern werden die gesammelten PET Abfälle gratis von PET Recycling Schweiz abgeholt. So entstehen jedes Jahr 2000 neue Sammelstellen.


Source: Pet Recycling Schweiz

PET-Bottles and what they are made of

PET-bottles are made of Polyethylene terephthalate. Polyethylene terephthalate is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods, thermoforming for manufacturing, and in combination with glass fiber for engineering resin.

Production

Polyethylene terephthalate is produced from ethylene glycol and dimethyl terephthalate. The majority of the world’s PET production is for synthetic fibers (in excess of 60%), with bottle production accounting for about 30% of global demand.

Ethylene glycol is an organic compound. It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odorless, colorless, sweet-tasting syrup. Ethylene glycol is moderately toxic.

Dimethyl terephthalate (DMT) is an organic compound. It is the diester formed from terephthalic acid and methanol. It is a white solid that melts to give a distillable colourless liquid.

Physical properties

PET in its natural state is a colorless, semi-crystalline resin. Based on how it is processed, PET can be semi-rigid to rigid, and it is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier to alcohol (requires additional “barrier” treatment) and solvents. It is strong and impact-resistant. PET becomes white when exposed to chloroform and also certain other chemicals such as toluene.

Source: AACC, Verein PRS, Wikipedia

Environemental pollution of PET

All plastic bottles use a lot of fossil fuels and pollute the environment. In fact, Americans buy more bottled water than any other nation in the world, adding 29 billion water bottles a year to the problem. In order to make all these bottles, manufacturers use 17 million barrels of crude oil. That’s enough oil to keep a million cars going for twelve months.

Imagine a water bottle filled a quarter of the way up with oil. That’s about how much oil was needed to produce the bottle.

So why don’t more people drink water straight from the kitchen faucet? Some people drink bottled water because they think it is better for them than water out of the tap, but that’s not true. In the United States and also in Switzerland, local governments make sure water from the faucet is safe. There is also growing concern that chemicals in the bottles themselves may leach into the water.

People love the convenience of bottled water. But maybe if they realized the problems it causes, they would try drinking from a glass at home or carrying water in a refillable steel container instead of plastic.

Plastic bottle recycling can help—instead of going out with the trash, plastic bottles can be turned into items like carpeting or cozy fleece clothing.

Unfortunately, for every six water bottles we use, only one makes it to the recycling bin. The rest are sent to landfills. Or, even worse, they end up as trash on the land and in rivers, lakes, and the ocean. Plastic bottles take many hundreds of years to disintegrate.

Water is good for you, so keep drinking it. But think about how often you use water bottles, and see if you can make a change. And yes, you can make a difference. Remember this: Recycling one plastic bottle can save enough energy to power a 60-watt light bulb for six hours.

Recyclingprocess

Here is Switzerland we can trust in recycling companies. Compared to other countries we do exceptionally well in recycling PET. About 83% of PET is recycled in our country and the numbers are rising. Since the early 2000’s multiple marketing campaigns have advertised the ecological and economic benefits of PET recycling. Those campaigns have proven to be very effective. Today it is clear that the majority of people do separate their rubbish from pet. Also the availability of specialised dumpsters contributes much to the high recycling rate.

From those trash cans the pet is collected whenever necessary and brought to a court where the bottles are stored until they can be recycled.

The blocks as seen in the picture above are later shredded into small chips. These chips can easily molten and progressed into a PET-bottle again.

All in all, the recycling of PET is a very interesting process that developed very well during the last decade. If only more things could be recycled with such great success….

Recycling und Produktionsprozess

Als erstes werden die Flaschen abgefüllt und verkauft. Nach dem Verkauf folgt die Sammlung der PET Flaschen. So ist es wichtig, dass die Flaschen in die richtigen Containers geworfen werden. PET Recycling Schweiz leeren in der ganzen Schweiz die Containers mit den leeren PET Flaschen und transportieren sie danach zu den Sortierzentren. Dort werden sie nach Farbe sortiert und zu 200-300 Kilogramm schweren Pressballen verarbeitet. Nach der Sortierung folgt die Rückgewinnung. Dabei werden die Flaschen zu Rezyklat verarbeitet. Die Ballen werden wieder aufgeschnitten und gelangen auf ein Metallabscheider. Dort entfernt man die Etiketten und scheidet diese aus. Danach kommen sie in eine Mühle, wo sie geschnetzelt werden. Nachher kommen sie in ein Wasserbecken, um das PET von den Deckeln zu trennen. Dabei sinkt das PET und die Deckel schwimmen oben auf. Sie kommen in eine Mischschnecke, wo sie gemischt werden mit 50%iger Lauge. Das führt dazu, dass das PET gereinigt wird. Nachher werden die sogenannten PET Flakes gewaschen und getrocknet. Zuletzt misst ein Laser die Struktur der Flakes und scheidet die letzten Fremdmaterialien aus. Danach geht’s zur Flaschenprodukton. Man erstellt zuerst mit Maschinen sogenannte Preforms, die danach zu den einzelnen Getränkeabfüllern transportiert werden. Die Preforms sind wesentlich kleiner, so können sie Massenweise transportiert werden. Dort werden sie dann in die gewünschte Form gebracht. Um die Form zu erreichen, werden die PET Molekülketten erhitzt auf 250 Grad. Sie sind dann so beweglich, dass sie formbar werden. Wenn sie danach abkühlen, frieren die Molekülketten wieder ein.

 Fazit

This project really changed the way we see the bottles we use every day. To know that we use such a high-tech product every day makes me kind of curious what long therm effects those man made objects will have on our ecosystem. The future will show how we handle our own waste.

Gille, Yannic, Yannick

Class Survey

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