Writing this up rather belatedly... As promised, I revisited melting PET plastic, in the hope of recreating what I had with epoxy (I think I'm going a different way with this now - I'll post soon - little glass cubes). This time I tried bottles rather than cartons, and I melted them slowly. Long story short, the results were a tiny bit better, but not much. Crystallisation appears to still be a problem, as is the fact that the melted plastic is very very viscous so pouring it is nigh-on impossible, especially as it hardens almost as soon as it is away from the heat. Another challenge is decomposition of the plastic where it heats unevenly. This releases toxic fumes, but more concerning, makes the plastic an unattractive brown colour ;)
One minor improvement, is that cooling the plastic really fast seems to reduce the extent of the crystallisation - which would make logical sense since you aren't giving it time to anneal. I got this sample that is reasonably well-melted and is also quite clear:
I think the horse is probably well-and-truly dead now, and I should just stop flogging it, but I think two last avenues I could explore would be the oven and/or a heat gun. The oven would likely give more even and predicable heating, but doesn't avoid the other issues. A heat gun might give more predictable heat, and would also allow me to bring the heat to the plastic in-situ and thereby avoid the pouring issue.
However, I think probably need to accept that I'm done with plastic for now. I'm already beginning to explore using glass planes as a replacement, which I will deal with in another blog entry.
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