The key difference between polystyrene and polypropylene is that the monomer for polystyrene is styrene, while the monomer for polypropylene is propylene.
Polymers are large molecules, which have the same structural unit repeating over and over. These repeating units are “monomers”. Monomers bind with each other via covalent bonds to form a polymer. Moreover, they have a high molecular weight and consist of over 10,000 atoms. In the synthesis process, or “polymerization”, we can obtain longer polymer chains. Thus, polystyrene and polypropylene are two such polymers.
What is Polystyrene?
Polystyrene is made out of the monomer styrene. Its IUPAC name is poly(1-phenylethene-1,2-diyl), and it is an aromatic polymer. Its long hydrocarbon chain has phenyl groups attached to every other carbon atom in polystyrene. Furthermore, according to the pattern in which the phenyl groups (pendant groups) attach to the carbon chain, there are three types of the polymer: isotactic (all phenyl groups are on the same side of the chain), syndiotactic (the phenyl groups are in two sides in an alternating pattern) and atactic (the phenyl groups attach in a random pattern).
Moreover, polystyrene is a vinyl polymer, and it is synthesized by free radical vinyl polymerization. Also, it is a hard and rigid material.
Polystyrene is useful in making toys, kitchen appliances, disposable drinking cups, packaging material, computer housing parts, etc. Moreover, we can recycle polystyrene. Though it is a plastic highly in use all over the world, it causes less environmental harm due to its ability to recycle.
What is Polypropylene?
Polypropylene is also a plastic polymer. Its monomer is propylene, which has three carbons and one double bond between two of those carbon atoms. We can manufacture this material from propylene gas in the presence of a catalyst such as titanium chloride. Furthermore, it is easy to produce, and we can manufacture it with high purity.
Polypropylene has the following important properties:
- High resistance to cracking, acids, organic solvents, electrolytes
- High melting point
- Has good dielectric properties
- High economic value
Due to the above properties, this material is useful for the production of pipes, containers, houseware, and packaging and automotive parts.
What is the Difference Between Polystyrene and Polypropylene?
Both polystyrene and polypropylene are useful polymer materials we use in our daily life. The key difference between polystyrene and polypropylene is that the monomer of polystyrene is styrene while the monomer of polypropylene is propylene. Furthermore, the pendant group of polystyrene is a phenyl group while the pendant group of polypropylene is a methyl group. These pendant groups decide the tacticity of the polymer.
Moreover, there is a difference between polystyrene and polypropylene in their manufacturing process too. We can manufacture polystyrene via free radical vinyl polymerization and polypropylene via chain-growth polymerization.
Below infographic summarizes the difference between polystyrene and polypropylene.
Summary – Polystyrene vs Polypropylene
In brief, polystyrene and polypropylene are very important polymer materials. The key difference between polystyrene and polypropylene is that the monomer of polystyrene is styrene while the monomer of polypropylene is propylene.
1. “Polypropylene.” Wikipedia, Wikimedia Foundation, 10 Mar. 2019, Available here.
2. Krzysztof Matyjaszewski, in Comprehensive Polymer Science and Supplements, 1989.
1. “Expanded polystyrene foam dunnage” By User:Acdx – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Polypropylene Wipe Detail” By BlueThunderTechnologies – Own work (CC BY-SA 4.0) via Commons Wikimedia