In order to achieve these properties and goals, thermally expandable particles (TEPs) have significantly played roles and has been included in the bigger picture. TEPs comprise of thermoplastic shell filled with liquid hydrocarbon. Heating them causes softening of shell material and also, gasification of the hydrocarbon liquid inside it. And in turn, the shell expands as the gas inside it pressurizes the softened shell from inside out, causing it to swell, 50 to 100 times of the initial volume. The shell stiffens and the particle remains in its expanded form, when heat is removed. Expansion temperatures vary from 70 to 285 degree centigrades depending on particle and grade.