Polyphenylethylene, also known as polyethylbenzene or polystyrene. In its natural state is very hard and brittle, the phenyl group (C<sub>6</sub>H<sub>5</sub> replacing a hydrogen atom) increases hardness (due to increased [[dispersion forces]]) but decreases density. However, gas can be blown through the liquid polymer during its formation to produce a foam, which is an excellent insulator (the phenyl group does not conduct heat very well) allowing it extensive application in disposable cups. | Polyphenylethylene, also known as polyethylbenzene or polystyrene. In its natural state is very hard and brittle, the phenyl group (C<sub>6</sub>H<sub>5</sub> replacing a hydrogen atom) increases hardness (due to increased [[dispersion forces]]) but decreases density. However, gas can be blown through the liquid polymer during its formation to produce a foam, which is an excellent insulator (the phenyl group does not conduct heat very well) allowing it extensive application in disposable cups. |