Thermocol is a commercial name like Coca-Cola. In 1951 the researchers of a German company named BASF successfully restructured chemical bonding of polystyrene (a synthetic petroleum product) molecules and developed a substance named stretch polystyrene. This substance was named Thermocol, which nowadays is manufactured through a simple process. Thermoplastic granules are expanded through application of steam and air. Expanded granules become much larger in size but remain very light.
Thermocol is a good resister of cold and heat but since it is a petroleum product it dissolves in any solvent of petroleum.