The world of plastics can be broadly classified into two types, thermo plastics and thermosetting plastics.
Thermo plastics are those that can be molded again and again. That is, under heat and pressure these types of plastics can be molded into desired shape any number of times, however, with a slight difference in quality. Good examples of thermo plastics include LDPE, HDPE, PP, and the like. The buckets you use, plastic covers, and plastic balls are all made of thermo plastics. One good quality of this type of plastics is that they can be safely recycled without any major damage to the environment.
Thermosetting plastics on the other hand are those plastics that can be molded to desired shape under pressure and heat but cannot be remolded like thermo plastics. Products made out of thermosetting plastics if damaged or broken can only be dumped in the waste yard. This type of plastics does not degrade easily and cause serious trouble to the environment. Good examples include the melamine ware commonly used as kitchen utensils.
