Question: what are the three main categories of plastics?
Answer: 1 – Polyethylene Terephthalate (PET or PETE or Polyester) ...  2 – High-Density Polyethylene (HDPE) ...  3 – Polyvinyl Chloride (PVC) ...  4 – Low-Density Polyethylene (LDPE) ...  5 – Polypropylene (PP) ...  6 – Polystyrene (PS) ...  7 – Other.