One of the most important aspects of the plastics industry, recycling allows us to builds brand new parts out of plastic items that have come to the end of their run.
Through wear-&-tear, mishandling, discoloration, age and other factors, plastic items undergo degradation which ultimately will make them no longer useful for their original purpose. Fortunately, thermoplastic resins such as polyethylene and polypropylene, materials we widely use, are capable of being melted multiple times and formed into new parts each time. This is a quality of the polymer chains, the long intertwined molecules that make up plastics and give plastic parts their characteristic stiffness and solidity. Thanks to the thermoplastic property, plastic resin remains in production over and over, each time being recreated into a new object.
Wikipedia has a great entry on plastics recycling. In the terminology used there, the kind of recycling process used at Thunderbird Plastics is called mechanical recycling, or “chop-and-wash“.