Drywall is a common building material typically made of a layer of gypsum plaster pressed between two thick sheets of paper, then kiln dried. Drywall is used globally for the finish construction of interior walls and ceilings.
Drywall is also commonly known as gypsum board, wallboard, plasterboard (USA,UK, Ireland, Australia), Gibraltar board or gib (New Zealand – GIB being a trademark of Winstone Wallboards), rock lath, Sheetrock (a trademark of United States Gypsum Company), gyproc (Canada, Australia, UK), pladur (Spain – after the Pladur brand), rigips (Germany and Central Europe – after the Rigips brand), alçıpan in Turkey, or simply board.
A drywall (gypsum wallboard) panel is made of a paper liner wrapped around an inner core made primarily from gypsum plaster, the semi-hydrous form of calcium sulfate (CaSO4·½ H2O). The raw gypsum, CaSO4·2 H2O, (mined or obtained from flue gas desulfurization (FGD)) must be calcined before use. Kettle or Flash calciners typically use natural gas today. The plaster is mixed with fiber (typically paper and/or fiberglass), plasticizer, foaming agent, potash as an accelerator, EDTA, starch or other chelate as a retarder, various additives that increase mildew and fire resistance (fiberglass or vermiculite), wax emulsion for lower water absorption and water. This is then formed by sandwiching a core of wet gypsum between two sheets of heavy paper or fiberglass mats. When the core sets and is dried in a large drying chamber, the sandwich becomes rigid and strong enough for use as a building material.
Drying chambers typically use natural gas today. To dry 1 MSF (1,000 square feet) of wallboard, between 1.75-2.49 million BTU is required. Depending on plant efficiency and energy costs, 25% to 45% of drywall cost today is related to energy, primarily natural gas. This is the main reason why organic dispersants/plasticisers are used i.e. to reduce the amount of water to produce gypsum slurry flow during wallboard manufacture.
Source: Wikipedia