[thomas253]

Hi Guys,

Thanks in advance for any help you are able to offer. I am not a chemistry student but rather a product design student who is working on a chemistry related problem and am struggling to find the answer or the right place to look.

The Problem:
Basically I am trying to better understand the differences between different plastics, more specifically the differences between Polyester, Polyurethane and Polystyrene specifically in terms of their chemical compatibility. Essentially if I have a block of each of these materials can I put then into a pot and melt them into one block. I assume the answer is no but I know there will be a lot of variables and more specific details that could mean the answer is not always 100% no.

Can anyone point me in the correct direction to a book or source of more information? Or possibly answer my questions?

Questions:
Can Polyester and Polyurethane be combined into a single material and under what circumstances?
Can Polyester and Polystyrene be combined into a single material and under what circumstances?
How do I go about understanding which what is possible to laminate and combine with what relatively quickly and superficially. Anyone recommend a textbook that is orientated to students from outside the field of Materials Science?

Thanks again in advance for any and all help.

[wildfyr]

Hi there, polymer chemist checking in.

This is in fact a very complicated question in its ramifications, and not one that really lends itself to picking up a textbook but I'll brute force an answer and tell you that no, you cannot simply melt any of these together and they will stay that way. Polymers are, on longer time scales, immiscible with one another if they are significantly different. Significant can even mean polyethylene and polypropylene, which are only different by a single carbon. Basically what happens on the micro-level is they seperate out like oil and water. This can takes minutes or months depending on what exactly is going on. This is a fundamental tenet of polymer chemistry. It also generally ruins the material properties of the mixture when they phase separate.

Different polymers can be covalently bound to one another. In that case, you will get nano-phase separation, which has its own unique properties, but this requires a strong knowledge of chemistry to understand and do correctly, and is not really what you are looking forward.

Now, you can laminate two polymers in a layer on top of one another, and they may stay nicely together in layers, since they are already phase separated. I am not an expert in that particular concept.

I'm sorry I can't help you more, but you are frankly asking questions about a difficult and subtle art that takes many years to learn. Making laminates is, in itself, a whole field within polymer chemistry.

You would be MUCH better off working with finding just one polymer that has the combination of properties you need, or perhaps using small molecule additives to adjust properties.

[thomas253]

Wildfyr, Thank you for your response. I am glad the answer is as complex as I expected it to be. And your answer was a great help although I know it´s a can of worms.

I know that if I stuck with a single polymer my problems would be ''Solved'' but the reality is the project lends itself to working with materials from a variety of recycled source and combining these. (I know recycling polymers is a whole new discussion).

The hope I get from your answer though is that theoretically if I (with the assistance of a far more experienced chemist) can specifically control the imput materials there is a chance that it would be possible to produce a controllable and usable output from a combined material made from different polymers.

P.S. I´m far more confident with composites and laminates but melting and chemical combination of materials is a different challenge.

[Corribus]

Now, you can laminate two polymers in a layer on top of one another, and they may stay nicely together in layers, since they are already phase separated. I am not an expert in that particular concept.

Typically a tie (adhesive) layer is used. Otherwise they easily delaminate. This is common practice in plastic packaging.

To the OP:

You may also melt-blend two different polymers by melting both and then mixing together. Whether they stay mixed will depend on their their compatibility. You can also incorporate multiple polymers together chemically into a single polymer by processes like grafting or co-polymerization. The latter is an entryway to block copolymers or alternating copolymers, etc.

You may find more general information about copolymers here: https://en.wikipedia.org/wiki/Copolymer.  About co-extrusion here: https://en.wikipedia.org/wiki/Plastics_extrusion#Coextrusion.