Hello,
well going back to my 2006 notes. my involvement is on using the actual plastic material was with extrusion and vaccum forming.
when i started my hobby, I wanted to use plastic that is typically discarded or recycled locally. my first problem is figuring out what the mystery plastic is. I recently discovered a weblink (that does plastic test) that helps me identify the mystery plastic. Later with a few sparse notes on plastic original formulatory that I came across and tested against the weblink-testing led me to realize that with knowing true original base, could at least figure out what the plastic is made from.
I have noted there is a common factor on my finding 'original' base material for thermoplastic (meltable and forming by heat). is always flammable.
My preferred plastic material is polyethylene (PE).
my problem stemmed on figuring out the base material; Unless someone published a plastic equivilant formulatory from 'original' base, you would be finding analysis includes one or two monomers from DOW corning. DOW corning is the one who discovered cheap way to distill-convert-extract sweet crude oil into about 85 percent of monomers used in our plastic productions.
however the properties of the plastic regardless of the crude oil based monomers, usually retains the the same original base properties that appears in the weblink plastic test identifications.
for example, cellouse nitrate as interested earlier.. burns fast, smelling camphor (aka mothballs). gives guessimate that this base is some sort of alcholic [burns fast and does not float] based extraction from citronella oil (extracted from lemongrass) or camphor oil (extracted from cedar wood). so going by history of cellouse nitrate use, has to be cedar extraction.
PE gives off parrafin type smell and floats in water... so is sort of wax based process. I know from my search results; PE is based on ethylene
which is derived from methane (methane is from cellouse fermentation-think brewing wood.) which burns clean. With
Polypropyethylene Polypropylene (
is from proprane which is 'chilled extraction' of natural gas ethanol), but gives acrid-disel odor, also floats which is wax based process.
Hey i am now going back in and see if there is new information on PE now ... my research was old... in 2006.
one thing of an note of my research does not involves thermoset class of plastics [beside the plastic test chart] because these materials are chemically made and requires additional chemicals to recycle the material.
R
edit:

my notes is no good!!!! updating above with new info. PE and PP in particular, PP is made from alcohol!! In another note that I found on PP, i went back to that orignal web site and foundit is removed.