Not if you're running a flame hot enough to guarantee complete combustion; this is the difference between a proper waste incinerator and a burn barrel.
Plastics are hydrocarbons; nothing special going on there.
We can burn plastic as fuel in a proper incinerator, the fuel can power the incinerator, and we can achieve a damn-near perpetual machine with the amount of plastics we have.
(I'm being facetious, of course)
Chlorinated plastics produce dioxins when burned.
there are many additives in plastics so often they're not only hydrocarbons. BPA, PCB, flame retardants, colors and UV protection, etc