PS glass roof with drinking hole Products marked PS are made of polystyrene. PS utensils are non-microwaveable. PS utensils have a heat resistance of -5 degrees Celsius to +70 degrees Celsius. In the event that the food reaches this temperature, the vessel wall will collapse. PS is a lower cost material, which allows for more economical packaging. It is also used to make so-called Swedish bowls, which are often found in Chinese restaurants, but in addition to its function as a hot food container, it is also used to package fat. It is also a popular material for buffets: plastic plates and cutlery (plastic forks, plastic knives, plastic spoons) are made from it.