Difference Between Polypropylene and Polycarbonate

Main Difference – Polypropylene vs Polycarbonate

Polypropylene and Polycarbonate are polymer compounds. Polymer compounds are large macromolecules made from small molecules known as monomers. The chemical process known as polymerization is used for the formation of a polymer out of monomers. Polypropylene is made from propylene monomers. Polycarbonate is made from Bisphenol A and phosgene monomers. These polymers are used for the production of a variety of items. The main difference between Polypropylene and Polycarbonate is that Polypropylene is formed by addition polymerization whereas Polycarbonate is formed by step-growth polymerization.

Key Areas Covered

1. What is Polypropylene
      – Definition, Production, Applications
2. What is Polycarbonate
      – Definition, Properties, Applications
3. What are the Similarities Between Polypropylene and Polycarbonate
      – Outline of Common Features
4. What is the Difference Between Polypropylene and Polycarbonate
      – Comparison of Key Differences

Key Terms: Addition Polymerization, Monomers, Polycarbonate, Polymer, Polymerization, Polypropene, Polypropylene, Step-Growth Polymerization, Tacticity

Difference Between Polypropylene and Polycarbonate - Comparison Summary

What is Polypropylene

Polypropylene, also known as polypropene, and is a polymer made out of propylene monomers and has many applications. Polypropylene is a thermoplastic polymer that has applications as both fibers and plastics. The general formula for polypropylene is [CH(CH3)CH2]n. Polypropylene softens when heated and can be remoulded into different shapes. Polypropylene is made from addition polymerization. The major application of this material is its use as a packaging material.

Polypropylene is cheap because it is one of the most recyclable plastics that are available. When the chemical structure of Polypropylene is considered, it has no double bonds in its polymer structure. Because Polypropylene has only sp3 hybridized carbon atoms. It is a solid material.

There are three types of polymers depending on the presence of a side group/pendant group (-CH3): Isotactic, Atactic and Syndiotactic. Isotactic polymer structure is composed of polymer chains containing the pendant group on the same side. Atactic polymer structure is composed of polymer chains containing methyl group in a random manner. In syndiotactic structure, the methyl groups are attached in an alternating pattern.

Difference Between Polypropylene and Polycarbonate

Figure 1: Structures of Polypropylene with Isotactic (above) and Syndiotactic (below) Tacticity

Some of the favorable properties of polypropylene include low density, good transparency, recyclability, and stretchability. Some common applications of polypropylene include the production of films for food packaging, textile industry (for the production of carpets, etc.), production consumer goods, etc.

Polypropylene is made via addition polymerization. The most common method of production is using Zeigler-Natta catalyst. It can be done in two different processes as bulk process and gas phase process. In bulk process, the polymerization takes place in liquid propene; later, the solid polymer particles are separated from the liquid and propene is recycled.

What is Polycarbonate

Polycarbonate is a synthetic resin where the polymer units are linked through carbonate linkages. Polycarbonate is a type of plastic formed from the reaction between Bisphenol A and phosgene. Both these monomers are not composed of carbonate groups. But after polymerization, the polymer chains are composed of carbonate linkages, which leads to name these polymers are polycarbonates.

Main Difference - Polypropylene vs Polycarbonate

Figure 2: Carbonate Linkages in Polycarbonate

Polycarbonate is composed of aromatic rings. Polycarbonate is available in different colors. Although these polymers have a transparent nature, these colored products can be translucent depending on the intensity of color.

The polymerization process of polycarbonate is a step growth polymerization. Here, a condensation reaction that involves two functional groups occurs (an unsaturated monomer is not involved). This polymer is a strong and transparent material. Toughness and optical clarity of polycarbonate make it suitable to be used for indoor and outdoor applications as well. Polycarbonate is easily machined. It also has good dimensional stability with a high impact strength.

Similarities Between Polypropylene and Polycarbonate

  • Both are polymer compounds.
  • Both are thermoplastic polymers.
  • Both are synthetic polymers.

Difference Between Polypropylene and Polycarbonate

Definition

Polypropylene: Polypropylene or polypropene is a polymer made out of propylene monomers. 

Polycarbonate: Polycarbonate is a synthetic resin whose polymer units are linked through carbonate linkages.

Monomer

Polypropylene: Polypropylene is made out of propylene monomers.

Polycarbonate: Polycarbonate is made out of Bisphenol A and phosgene.

Polymerization

Polypropylene: Polypropylene is produced by addition polymerization.

Polycarbonate: Polycarbonate is produced by step-growth/condensation polymerization.

Side Groups

Polypropylene: Polypropylene is composed of polymer chains attached to methyl groups as side groups.

Polycarbonate: Polycarbonate is composed of polymer chains attached to aromatic rings as side groups.

Machinability

Polypropylene: Polypropylene is difficult to machine.

Polycarbonate: Polycarbonate is easily machined.

Uses

Polypropylene: Polypropylene is used as a packaging material.

Polycarbonate: Polycarbonate is used as machine guards and indoor/outdoor applications.

Conclusion

Polypropylene and Polycarbonate are polymer compounds. They are made by the polymerization of monomers. Polypropylene is mainly used as a packaging material. Polycarbonate has a variety of uses depending on its properties. The main difference between Polypropylene and Polycarbonate is that Polypropylene is formed from addition polymerization whereas Polycarbonate is formed from step-growth polymerization.

References:

1. Lazonby, John. “Poly(Propene) (Polypropylene).” The Essential Chemical Industry online, Available here.
2. “Vanderveer Industrial Plastics.” Vanderveer Industrial Plastics, Available here.
3. “Polypropylene.” Wikipedia, Wikimedia Foundation, 7 Nov. 2017, Available here.

Image Courtesy:

1. “Polypropylene tacticity” By RicHard-59 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Polycarbonate PC” By Original uploader was PulkoCitron at fr.wikipedia – Transferred from fr.wikipedia; transferred to Commons by User:Bloody-libu using CommonsHelper (CC BY-SA 2.5) via Commons Wikimedia

About the Author: Madhusha

Madhusha is a BSc (Hons) graduate in the field of Biological Sciences and is currently pursuing for her Masters in Industrial and Environmental Chemistry. Her interest areas for writing and research include Biochemistry and Environmental Chemistry.

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