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Compression moulding PET

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Sam Gueterbock samgueterbock

Compression moulding PET

05/11/2018 at 21:52

Hello everyone! I’ve recently set up a shredder and compression oven at a local school, but have encountered a huge amount of difficulty working with PET bottles.

Has anyone had any success using PET in the compression machine? I’ve even tried using plasticisers which lower the necessary temperature slightly and I still encounter problems like burning before melting.

I know about the narrow temperature range associated with PET but wonder whether this might be a step too far for this simple machine.

I’m persisting because I know PET sheet compression moulding is possible (despite it more commonly being extruded) because there is a  company here in the UK which makes compress PET panels. (In the image below)

Any advice/thought would be much appreciated!


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07/11/2018 at 09:15

Hey @samguterbock !

PET is the hardest to work with !
why? because of 2 types of degradations while trying to put to melt

the fist up is hydrolysis provoqked by the presence of water… you need to preheat around50-80°C for 15min (i reckon) your PET in order for it to dehydrate

then second up is the thermal degradation (250°C-300°C)

hope it helped !

21/11/2018 at 18:20

Thanks for the info!  It’s definitely difficult, but do you think it is impossible with these machines?

08/12/2018 at 23:44

Hey @samgueterbock PET is not a forgiving material. Even in the industry that makes PET bottles , with all the high tech costly equipment, they have the problem of degradation.
Compression molding is a low process. Meaningin heats the material slowly and cools it down slowly.
It would be great if you could share more about your experiment to have a better idea.

12/12/2018 at 15:46

Hello guys. I’m right now in Zambia, south of Africa, and would be highly interested in you results of moulding PET. Here all plastic used is thrown in the nature, as there is no recycling industry nearby… And it’s composed of PET plastic bottles for 90% of the trash.

So I’m willing to start the Precious Plastic experiment, but only if I can process PET, which seems more than complicated…

Any update on this pre-heat technique ? Someone tried it with the Precious Plastic equipment ?



13/12/2018 at 07:46

I’m working on PET at my shop too. I’ve found extruding PET that hasn’t been dried makes a very brittle and crumbly product. The problem seems to be water! It hydrates and needs energy (heat) to dehydrate it. I’m going to try desiccants in a container with flakes to see if that will do the trick, as that would be more cost effective than a heat driven drying process.

Additionally, the polymer length of PET is different depending on the product. PET bottles will have a longer polymer length (and better recycling success) than a PET clamshell (for holding fruit). This is why many recyclers take plastic bottles and not clamshells or other types of PET.

If anyone has success, I’ll be looking forward to hearing about it!

20/08/2019 at 19:30

Hey emmsclaire! Any news on your experiments with PET?  Have you been able to successfully produce any products?

24/08/2019 at 19:00

We recycle pet in massive quantities (over 1000 tonnes/ month here in India)
1. You can try using anti oxidants (2 %w/w)
2. Pre heating is must and that material should immediately be shifted to moulding to extrusion process after pre heating ( warm material)
Water and oxygen destroys PET, or else it is one of the best plastics. So keep it away from both

Samsonite is making luggage shells from recycled PET.

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