Key difference - polyester vs. polypropylene

Polyester and polypropylene are polymer materials. They are used on different occasions depending on their chemical and physical properties. Polyester is produced by condensation polymerization of a dicarboxylic acid and a diol. Polypropylene is made by the addition polymerization of propylene. Polyester materials are widely used in the textile industry. Polypropylene is mainly used as a packaging material. The main difference between polyester and polypropylene is that polyester can absorb a certain amount of water, while polypropylene does not absorb water at all.

Key areas covered

1. What is polyester - definition, manufacture, general properties 2. What is polypropylene - definition, general properties, advantages 3. What is the difference between polyester and polypropylene - comparison of the main differences

Key Terms: addition polymerization, condensation polymerization, dicarboxylic acid, diol, ester, hydrophobicity, monomer, polyester, polymer, polypropylene

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 made up of ester groups in the main chain. Chemically, polyesters consist 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 that form esters results in the formation of a polyester.

Polyesters are very 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 materials, etc.

Manufacturing process

The polyester manufacturing process involves two main steps: making the monomer and polymerizing the monomer.

• Making Monomer - This can be done in two ways. One is through direct esterification reaction. This is started by the acid. The other way is to start from dimethyl ester. Here the dimethyl ester goes through a transesterification reaction. This takes place in the presence of catalysts.
• Polymerization of Monomer - Polycondensation of monomer is obtained by one of the methods mentioned above.

Figure 1: Condensation reaction between a dicarboxylic acid and a diol

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

What is polypropylene?

Polypropylene is a thermoplastic polymer that is used as fibers and plastics . It consists of propylene monomer. The general formula for polypropylene is [CH (CH ₃ ) CH ₂ ] _n . Polypropylene softens when heated and can be formed into various shapes. Polypropylene is made by addition polymerization. The main application of this material is its use as a packaging material.

This polymer material can be used to make containers for microwave ovens. Polypropylene does not react with water and most chemicals. Polypropylene is considered a tough material. It is also very resistant to electricity. So it's a good electrical insulator.

Figure 2: Laboratory items made of polypropylene

Polypropylene is easy to customize. We can add dyes when making polypropylene to create a colorful polymer material. In contrast to other plastics, polypropylene does not absorb water due to its hydrophobicity. Polypropylene is light in weight and also flexible.

Difference between polyester and polypropylene

definition

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

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

Monomer

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

Polypropylene: The monomer used to manufacture polypropylene is propylene.

production

Polyester: Polyesters are formed by condensation polymerization.

Polypropylene: Polypropylene is formed by addition polymerization.

Water absorption

Polyester: Polyester absorbs a certain amount of water.

Polypropylene: Polypropylene does not absorb water.

Nature of the polymer

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

Polypropylene: Polypropylene is an aliphatic polymer.

diploma

Both polyester and polypropylene are polymers. Polyester is formed by condensation polymerization between a dicarboxylic acid and a diol. Polypropylene is formed by the addition polymerization of propylene monomers. The main difference between polyester and polypropylene is that polyester can absorb a certain amount of water, while polypropylene does not absorb water at all.

References:

1. Lazonby, John. "Polyester." The Essential Chemical Industry online, available here .2. "What is polyester?" What is polyester | What is polyester, available here .3. Johnson, Todd. “Learn more about the basics of the plastic resin polypropylene.” ThoughtCo, available here .4. "Polypropylene." Wikipedia, Wikimedia Foundation, October 26, 2017, available here .

Image courtesy:

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