Difference Between Polyester and Polypropylene

Main Difference – Polyester vs Polypropylene

Polyester and polypropylene are polymer materials. They are used in different occasions depending on their chemical and physical properties. The production of polyester is through condensation polymerization of a dicarboxylic acid and a diol. Polypropylene is produced via addition polymerization of propylene. Polyester materials are highly used in textile industry. Polypropylene has its major application as a packaging material. The main difference between polyester and polypropylene is that polyesters can absorb some amount of water whereas polypropylene does not absorb water at all.

Key Areas Covered

1. What is Polyester
      – Definition, Production, General Properties
2. What is Polypropylene
     – Definition, General Properties, Benefits
3. What is the Difference Between Polyester and Polypropylene
      – Comparison of Key Differences

Key Terms: Addition Polymerization, Condensation Polymerization, Dicarboxylic Acid, Diol, Ester, Hydrophobicity, Monomer, Polyester, Polymer, Polypropylene

Difference Between Polyester and Polypropylene - Comparison Summary

What is Polyester

Polyesters are polymers formed from the condensation polymerization between a dicarboxylic acid and a diol. Polyester is a common name used to describe long-chain polymers composed of ester groups in the main chain. Polyesters are chemically composed of at least 85% by weight of an ester and a dihydric alcohol and a terephthalic acid. In other words, the reaction between carboxylic acids and alcohols which forms esters cause the formation of a polyester.

Polyesters are highly useful polymers due to their important properties such as high strength, high durability, hydrophobic nature and quick drying. Polyester is useful as fibers, films, packaging material, etc.

Production Process

The production process of polyester includes two major steps: production of monomer and polymerization of monomer.

  • Production of monomer – This can be done in two ways. One is by direct esterification reaction. This is started from the acid. The other way is to start from dimethyl ester. Here, the dimethyl ester undergoes ester interchange reaction. It is done in the presence of catalysts.
  • Polymerization of monomer – The polycondensation of monomer is obtained from one of above methods.
Key Difference - Polyester vs Polypropylene

Figure 1: Condensation Reaction between a Dicarboxylic Acid and a Diol

Polyester fibers are very strong, and their durability is high. Due to this reason, polyesters are often resistant to chemicals, stretching, shrinking, etc. The most common applications of polyester are in the textile industry and food industry (for food packaging).

What is Polypropylene

Polypropylene is a thermoplastic polymer that has applications as fibers and plastics. It is made out of propylene monomer. 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.

This polymer material can be used for making containers for the microwave oven. Polypropylene does not react with water and most chemicals. Polypropylene is considered as a tough material. It is also highly resistant to electricity. So it is a good electrical insulator.

Difference Between Polyester and Polypropylene

Figure 2: Laboratory Items made from Polypropylene

Polypropylene is easy to customize. We can add dye during the manufacturing of polypropylene in order to obtain colorful polymer material. Unlike other plastics, polypropylene does not absorb water due to its hydrophobicity. Polypropylene has a light weight and is flexible as well.

Difference Between Polyester and Polypropylene

Definition

Polyester: Polyesters are polymers formed from the condensation polymerization between a dicarboxylic acid and a diol.

Polypropylene: Polypropylene is a thermoplastic polymer material that has applications as fibers and plastics.

Monomer

Polyester: Monomers for the production of polyester are dicarboxylic acids and diols.

Polypropylene: Monomer for the production of polypropylene is propylene.

Production

Polyester: Polyesters are formed by condensation polymerization.

Polypropylene: Polypropylene is formed by addition polymerization.

Water Absorption

Polyester: Polyesters absorbs some amount of water.

Polypropylene: Polypropylene does not absorb water.

Nature of Polymer

Polyester: Polyester can be found as aliphatic polymers, semi-aromatic polymers, and aromatic polymers.

Polypropylene: Polypropylene is an aliphatic polymer.

Conclusion                                                              

Both polyester and polypropylene are polymers. Polyester is formed via condensation polymerization between a dicarboxylic acid and a diol. Polypropylene is formed via addition polymerization of propylene monomers. The main difference between polyester and polypropylene is that polyesters can absorb some amount of water whereas polypropylene does not absorb water at all.

References:

1. Lazonby, John. “Polyesters.” The Essential Chemical Industry online, Available here.
2. “What is Polyester.” What is Polyester | What is Polyester, Available here.
3. Johnson, Todd. “Learn About the Basics of the Plastic Resin Polypropylene.” ThoughtCo, Available here.
4. “Polypropylene.” Wikipedia, Wikimedia Foundation, 26 Oct. 2017, Available here.

Image Courtesy:

1. “CondensationPolymerization Polyester” By MaChe (talk) – Own work (Public Domain) via Commons Wikimedia
2. “PolypropyleneItemsForLaboratoryUse” By DED Biotechnology – Own work (CC BY-SA 4.0) 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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