PS is a flexible plastic, called Polystyrene, formed from styrene polymerization reaction.
- Hard, transparent, tasteless, blazed up with unstable flame.
- Colorless and easy to color, eye-catching appearance, easy to process by pressing and injection molding (processing temperature is about 180 - 20000C).
- PS’s mechanical properties are relied on degree of polymerization. PS has a very low molecular weight and low tensile strength. When the molecular weight increases, then the mechanical strength increases and the brittleness decreases. If there is a certain degree of polymerization, the mechanical property is reduced. The tensile strength will be impaired if the temperature rises. The relative elongation will start to increase when temperature reaches 80oC. Over that temperature, PS will become soft and sticky like rubber. Therefore, PS is only used at temperatures lower than 80°C.
- PS is very difficult to be recycled.
- PS is used to produce the plastic food-grade containers, CD cases, DVDs, children's toys, computers, hair dryers, and kitchen appliances.
- In the plastic forming industry, PS is generally used to produce plastic boxes, plastic cups, plastic bowls, plastic candy trays due to its hard and brittle nature, very light, easy to shape into eye-catching products. However, PS products are not recommended to contain hot foods (above 700C) because large amounts of Monostyren are released at high temperature condition, resulting in liver impairment. Therefore, PS plastic trays should not be used to store water, high fat foods, pickles, and vinegar.
Currently, high impact polystyrene (HIPS) is used to replace PS and safer for food packaging.