If you ask my chemistry professor, there is only one category of truly recyclable plastic: thermoplastic. Within that category I think he specifically mentioned polypropylene, because it doesn’t require the addition of new plastic to be stable after reforming into a new plastic product. Unfortunately that one rarely gets recycled because it’s used for milk jugs and such, and food contamination is too big a hassle for people to deal with when there’s all this shiny new plastic waiting to be used

I’m a little bit drunk right now so my memory is probably not the best, you should definitely not take what I said as perfect fact xD