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Crystal clear PET plastic ?

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This topic contains 4 replies, has 4 voices, and was last updated by  Guy Verstraeten 7 months ago.

Abderraouf Mehdi Bouhali armbouhali

Crystal clear PET plastic ?

25/12/2017 at 21:59

Hello everyone,

Is there a way to work with PET plastic and keep it transparent ? The crystallization behaviour makes it difficult for a beginner like me.

How is crystal clear PET created at the industrial level ?
Does the cooling time have any effect in reducing the crystallization rate and thus making it less opaque/transparent enough ?

What about other plastic types that can be found in their transparent form (bags, food containers, packaging) ? What other rules apply to them ?

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26/12/2017 at 03:05

@armbouhali I did some searching and found it could be your cooling down times? have a look at this https://www.ptonline.com/columns/cooling-tips-for-crystalline-polymers

26/12/2017 at 10:50

@plastikfantastik Thank you for the article 🙂
It seems very counter intuitive for me. Where we generally cool molded plastics quickly to give it a stable shape that is easy to work/polish/finish, but as this guy says it’s the opposite that should be done !

An even cooling is what is needed to reduce crystallization. and since plastics are poor heat conductors, they need much more time to cool evenly. To determine the minimum required cooling rate and time, we may need first to provide a circulating heat oven, then measure the maximum thickness that can be found in the mold to estimate the cooling time needed by that specific plastic.

Has anyone ever tried to slow-cool molded plastics ?
I don’t mean by slow-cooling to let the plastic cool in ambient air, the difference in temperature is already large enough to trigger the crystallization. I mean cooling using an oven by slowly decreasing temperatures until the state where the polymer cools completely under a specific temperature (to find) is reached.

Here’s an interesting topic for you guys who have the compression machine already built. this time I guess the mold should also be heated and cooled along with the melted plastic (maybe the way the compression v1.0 worked in the past ?

By the time I have the necessary tools set up, I hope somebody else starts working on this issue soon 🙂

28/12/2017 at 13:33

It’d be great if somebody who knows what they are talking about (not me!) could make a recipe book, with all the heating and cooling info!

24/09/2018 at 14:16

This is interesting because PET is all over the place in bottles but how to keep it transparent?  Knowing this could be of big importance if one want to make things like transparent objects or sheet (plate) material.  I wonder there is a good way to keep it transparent?  Someone?

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