The polypropylene sheets are made by the polymerization of the propylene gas in the presence of a catalyst system. These polymerization conditions are set by the polymer grade that is to be produced. There are many production processes for the preparation of these sheets. These processes are done in the gas phase or the liquid phase, depending on their availability. But gas phase polymerization is less expensive and more flexible and also accommodates a large number of catalysts. This process is mostly used in the modern technologies and the plants producing polypropylene.