What is the difference between polystyrene (ps) and polypropylene (pp) in regards to resistance to acids/bases/chemicals?


Polypropylene and polystyrene are two types of commonly used polymers in the manufacture of plastic laboratory consumables. Polymers are large molecules that have the same structural unit repeating over and over.  The repeating units are called monomers. Polypropylene and polystyrene are both similar in many applications, but there are some inherent differences between them that make them more appropriate for specific applications.


Polypropylene, also known as PP, is a thermoplastic polymer. It is commonly used to manufacture plastic laboratory supplies like beakers, bottles, flasks, specimen containers, test tubes, and many others. Polypropylene is exceptionally tough, unbreakable, flexable and resistant to many chemicals, acids, and bases. It also has a high level of heat resistance. Depending on the grade, polypropylene has a melting point of 130 °C (266 °F) up to 171 °C (340 °F). Many polypropylene products are autoclavable due to this high level of heat resistance. In contrast with polystyrene products, which are disposed of after only a single use, polypropylene can be reused over and over again without having to replace them. Therefore, polypropylene products can be considered as cost effective alternatives to their glass equivalent. There are however still many applications where glass is still preferred and necessary. The durability, high chemical resistance, and high level of temperature tolerance of polypropylene products make them very versatile in many laboratory and industrial applications.


Polystyrene also identified as PS, is a polymer made from the monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum. At room temperature, polystyrene is normally a solid thermoplastic, but can be melted at higher temperature for extrusion, then resolidified. Styrene is an aromatic monomer, and polystyrene is an aromatic polymer. Polystyrene is a hard and rigid material used to make toys, kitchen appliances, disposable drinking cups, packaging material, computer housing parts, etc. It is a highly used plastic all over the world because it is usually offered at a lower price point than many other plastics. Polystyrene is environmental friendly because it can be recycled. Although polystyrene offers some resistance to acids and bases, it is not as resistant against some chemicals as polypropylene. Polystyrene products are usually consumed in large quantities as they cannot withstand heat above 100°C and are disposed of after only a single use. Polystyrene is great for general sample storage and transport and is commonly used in lab supplies such as test tubes, microplates, and petri dishes due to is glass like transparency.


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