How do plastisols work? What about PVC in general?

[sonambulo]

Part I

So, I asked a similar question about this over in OT. What it boils down to is I want to make slush cast toys with something far less toxic than PVC and preferably biodegradable. I was looking for a more 'off the shelf' solution to my problem but it seems that what I am looking for is not currently on the market.

Anyways I was wondering if anyone could explain to me in layman's terms how plastisols that are currently on the market work? From what I understand, plastisol consists of pvc particles (no idea how small) suspended in a plasticizer. When the mix is heated, the whole solution hardens. Now what kind of chemical reaction is taking place exactly? The PVC has not reached it's melting point so it would seem that the plasticizer is the part of the mix that is undergoing chemical reaction. I read that the plasticizer is 'filling in the gaps' inside of and between the PVC molecules. Is this correct or am I erroneous? Can anyone explain the chemical reaction in layman's terms? I also understand that a plastisol's rigidity is determined by the amount of PVC included rather than the type of plastic...is this correct?

Now if anyone knows of a sustainable/biodegradable off the shelf plastisol equivalent then that is that. However I am unable to find one on the market. What's to stop someone from 'rolling their own? Would it not be possible to use particles of another rigid plastic suspended in a plasticizer to duplicate the effect?

Part II

As for PVC in general, I hear all kinds of misinformation. Some people say it's horrible from production, to use, to disposal. Other people say that it's fine so long as it's phthalate free and incinerated properly. I can't really find conclusive information on this one. Can anyone offer help here? I would really love to use already established materials rather than head for exotics IF they are safe. However I will hold off for something safer/sustainable if PVC really is that bad.

 

[CycloWizard]

Basically, polymers, plasticizers, and solvents have complex molecular interactions. In solution theory, these are generally collected into a "solubility parameter" between two of the species in the system (in this case, PVC and plasticizer). When the solubility parameter is favorable, the species are more or less completely miscible, the enthalpy of mixing is very low, and mixing can even be an exothermic process. So, even if the mold is not heated to the melting point of the mixture, the mixture can still heat itself up to its mixing point during mixing. This technique is also used during extrusion and other polymer processing. Thus, it's not necessarily undergoing any chemical reaction, though an appropriate material could be used as a bonding agent to ensure proper incorporation of the plasticizer and add to the exothermicity of mixing.

As the species come together, the material becomes stiffer due to plasticization effects. I wrote a paper on plasticization effects in PVC about 8-9 years ago if you are interested. PVC is a very highly plasticized polymer that does some strange stuff, so tons of stuff is available in the literature.

As far as Part II, there are many different kinds of PVCs and processes to make PVC, so it's not really safe to generalize either way. In general, I wouldn't give my kid a PVC pipe to chew on or bottle to drink from, but other than that it's probably going to be pretty safe.

 

[gorobei]

bio plastics or cornstarch plastics are somewhat better for sustainablility, but wont last that long or have the full ductile property of pvc.

 

[sonambulo]

As the species come together, the material becomes stiffer due to plasticization effects. I wrote a paper on plasticization effects in PVC about 8-9 years ago if you are interested. PVC is a very highly plasticized polymer that does some strange stuff, so tons of stuff is available in the literature.

As far as Part II, there are many different kinds of PVCs and processes to make PVC, so it's not really safe to generalize either way. In general, I wouldn't give my kid a PVC pipe to chew on or bottle to drink from, but other than that it's probably going to be pretty safe.

Thank you! I would definitely be interested in reading your paper. I'd also be interested in the titles of any textbooks you have used while learning about plastics especially producing finished products from plastics. I'm captivated not only by slush casted plastics but also the products that can be made by blow molding.

bio plastics or cornstarch plastics are somewhat better for sustainablility, but wont last that long or have the full ductile property of pvc.

That's totally fine. I'm interested in making rigid statues and figurines that will simply sit on a shelf for their lifetime. I'd assume that when the owner is done with them they will simply be thrown out long term. I would love if they were able to ultimately biodegrade.

By the way, what was your specific field of study? Chemistry? Industrial Engineering? Self taught?

edit: One more thing. Any info on dealing with plastisol? How do I clean it up if spilled, dispose of it, dye it, etc?