There are seven primary plastic resin types used in injection molding: 1. PET or PETE (Polyethylene Terephthalate) 2. HDPE (High-Density Polyethylene) 3. PVC (Polyvinyl Chloride) 4. LDPE (Low-Density Polyethylene) 5. PP (Polypropylene) 6. PS (Polystyrene) 7. Ryton & Kynar (and Other)