Plastics can be classified into two main categories: thermoplastics and thermosets. Thermoplastics, such as polyethylene and polypropylene, soften when heated and harden when cooled, allowing them to be easily melted down and reshaped. Thermosets, like polyester and epoxy, permanently harden after being heated and molded and cannot be remelted or remolded once solidified. This document provides information on classifying plastics for a building materials course at the School of Architecture, Delhi Technical Campus.