It's not that difficult to make plastic from strong sugars. The trick is to make plastic from less expensive weak sugars like wood chips. One company making plastic from wood chips has given up on a quick biodegradable action because of shelf life requirements of food.
Here is another link in the news:
Many plastics can be used for melting, but not all. Basically there are 2 types to distinguish here; thermoplastics and thermosetting plastics.
Thermoplastics can be heated and shaped. Examples are HDPE, LDPE, PLA, and PP (see the Wikipedia link for a longer list of types)
Thermosetting plastics harden or burn when heated. Examples are Phenolic (PF) resins, ...