Author Topic: PET Plastic (Thermoformed Food Clamshells, for example)  (Read 321 times)

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Offline ldichiara

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PET Plastic (Thermoformed Food Clamshells, for example)
« on: June 06, 2018, 05:50:54 pm »
Hi All -
I am trying to get a realistic PET material to render clear plastic similar to a thermoform clamshell for food or a soda bottle - but with a thinner wall thickness. Has anyone done a material to replicate this? I"ve been playing with the settings but my plastics are coming out to look much more like a polycarbonate which isn't what I am after.
There are a few materials I've found in the cloud but they too come across as being a more rigid type of plastic.

Thank you -

Lenny

Offline DriesV

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Re: PET Plastic (Thermoformed Food Clamshells, for example)
« Reply #1 on: June 12, 2018, 01:33:01 am »
Interesting question. :)

Let's look at the optical properties of PC and PET first:
  • Polycarbonate (PC) is an amorphous and thus naturally transparent thermoplastic polymer. It has excellent transmissivity and stable optical qualities. Hence the material is often used for prescription lenses.
  • Polyethylene terephthalate (PET), on the other hand, has a crystallinity varying from amorphous to fairly high crystalline. This means that PET can be highly transparent and transmissive, but especially thicker sections tend to be more opaque or translucent and colored.

What this means for KeyShot:
  • PC can accurately be represented by using 'Glass (Solid)' or 'Dielectric', since PC's optical properties are fairly similar to glass.
  • PET can accurately be represented by using 'Plastic (Cloudy)', since PET exhibits some translucency and scattering in thicker sections. 'Plastic (Cloudy)' allows for fine control over the amount of cloudiness (scattering) and transmission color. It can also be used for more crystalline plastics (more translucent), such as polyethylene and polypropylene.

How to get started in KeyShot:
The best starting point for PET is to drag and drop the 'Plastic Polypropylene Shiny 3mm' material from the KeyShot 7 Library onto your model.
The three most important parameters are Transmission, Transparency and Cloudiness. These parameters work in unison, and changing one will impact the effect of the others.
  • Transmission: The transparent color of the material
  • Transparency distance: The distance at which the above color is achieved. Lower distance results in darker and more saturated material, higher distance results in brighter and less saturated material.
  • Cloudiness: The amount of scattering inside the material. Lower cloudiness is more transparent, higher cloudiness is more translucent.
You will probably want to drop the Cloudiness value to get a realistic PET material.

I hope that helps.
P.S. It would probably make sense to add a few PET materials to the KeyShot Library. :)

Dries
« Last Edit: June 12, 2018, 01:44:29 am by DriesV »

Offline DriesV

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Re: PET Plastic (Thermoformed Food Clamshells, for example)
« Reply #2 on: June 12, 2018, 02:47:51 am »
Here is a quick comparison between Dielectric and Cloudy Plastic using a model I found on GrabCAD.

Dries

Offline mattjgerard

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Re: PET Plastic (Thermoformed Food Clamshells, for example)
« Reply #3 on: June 12, 2018, 06:46:03 am »
That's a great explanation of the differences. I have to read up on the dielectrics, I know I could be using them more than I am, I just don't know how they work. I'm bookmarking this thread.