There is a tendency to utilize underground space for the less ornamental purposes of civilization; there is the Metropolitan Railway in London, for instance, there are new electric railways, there are subways, there are underground workrooms and restaurants, and they increase and multiply.
Polystyrene can be naturally transparent, but can be colored with colorants. Uses include protective packaging (such as packing peanuts and CD and DVD cases), containers (such as clamshells), lids, bottles, trays, tumblers, and disposable cutlery.
The choice of material varies depending upon application. 1  High-density polyethylene (HDPE) is the most widely used resin for plastic bottles. This material is economical, impact resistant, and provides a good moisture barrier. 2  Low-density polyethylene (LDPE) is similar to HDPE in composition.