Difference Between Nylon and Polyester

Main Difference – Nylon vs Polyester

Nylon and polyester are polymers. A polymer is a macromolecule that is made out of a high number of monomers. Monomers can bind covalently with each other to form a polymer molecule. The properties of a polymer mainly depend on the types and the arrangement of monomers present in the polymer molecule. Since there are thousands of natural polymers and synthetic polymers, these macromolecules can be grouped based on different properties. The main difference between them is that nylon is essentially composed of nitrogen atoms in its structure whereas polyester has no nitrogen atoms.

Key Areas Covered

1. What is Nylon
      – Definition, Properties, and Uses
2. What is Polyester
      – Definition, Properties, and Uses
3. What are the Similarities Between Nylon and Polyester
      – Outline of Common Features
4. What is the Difference Between Nylon and Polyester
      – Comparison of Key Differences

Key Terms: Monomer, Nylon, Polyester, Polymer, Saturated Polyesters, Unsaturated Polyesters

What is Nylon

Nylon is a common name used for a class of polymer molecules that are composed of polyamides. This group of polymers includes plastics. They are known as thermoplastics due to their thermal properties. Some of the members of this group are shown below.

Nylon 6
Nylon 6,6
Nylon 6,8
Nylon 6,10

Nylons belong to condensation polymers due to the method of synthesis. Nylon polymers are made by condensation polymerization. Monomers involved in the production of nylon are diamines and dicarboxylic acids. The condensation polymerization of these two monomers will form peptide bonds. A water molecule is produced per each peptide bond as a byproduct.

Most of the nylon forms are composed of symmetrical backbones and are semi-crystalline. This makes nylons very good fibers. The name of the form of nylon is given according to the number of carbon atoms present in the diamine and the dicarboxylic acid monomers. For example, in nylon 6,6, there are six carbon atoms in the dicarboxylic acid and six carbon atoms in the diamine.

Figure 1: Structure of Nylon 6 and Nylon 6,6

Generally, nylons are tough materials. This material has a good chemical and thermal resistance. Nylons can be used in high-temperature environments. The maximum temperature where nylon can be used is at 185^oC. The glass transition temperature of nylon is about 45^oC. The glass transition temperature of a polymer is the temperature at which the polymer transitions from a hard, glassy material to a soft, rubbery material.

Nylon is used in the production of film and fiber. It is also used as a moulding compound. Apart from that, nylons can be blended with other plastics to improve their performance. Nylon resins are used in automobile industry. It is used as a packaging material where an oxygen barrier is required for food packaging.

What is Polyester

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 formed from the condensation reaction between dicarboxylic acids and alcohols (diols). Polyesters are mainly of two types as saturated polyesters and unsaturated polyesters. Saturated polyesters are composed of saturated backbones. Since they are saturated, these polyesters are less or not reactive. Unsaturated polyesters are composed of vinyl unsaturation. Therefore, these polyester materials are very reactive.

Figure 2: Polyester Material

Polyester fibers are extremely strong. It is a durable material. That is because polyesters are often resistant to chemicals, stretching, shrinking, etc. The most common applications of polyester are in the textile industry, food industry (for food packaging), etc.

Similarities Between Nylon and Polyester

Both are polymer materials.
Both are produced via condensation polymerization.
Both synthesis mechanisms produce water molecules as byproducts.
Both are very important in different industries.

Definition

Nylon: Nylon is a common name used for a class of polymer molecules that are composed of polyamides.

Polyester: Polyester is a common name used to describe long-chain polymers composed of ester groups in the main chain.

Chemical Name

Nylon: Nylons are also called polyamides due to the presence of amide groups.

Polyester: Polyesters are also called polyethylene terephthalate (PET).

Monomers

Nylon: The monomers that are involved in the production of nylon are diamines and dicarboxylic acids.

Polyester: The monomers that are involved in the production of polyester are dicarboxylic acids and diols.

Nitrogen Atoms

Nylon: Nylon polymers are essentially composed of nitrogen atoms.

Polyester: Polyesters have no nitrogen atoms in their chemical structure.

Conclusion

Nylons and polyesters are very useful polymer materials in industries. Although these materials are sometimes used for the same purpose due to somewhat similar properties, they have different chemical structures. The main difference between nylon and polyesters is that nylon is essentially composed of nitrogen atoms in its structure whereas polyester has no nitrogen atoms.

References:

1. “Nylons.” The Polymer Science Learning Center, Available here.
2. “What is Polyester.” What is Polyester, Available here.
3. Lazonby, John. “Polyesters.” The Essential Chemical Industry online, Available here.

Image Courtesy:

1. “Nylon6 and Nylon 66” By Michael Ströck (mstroeck) at en.wikipedia – Transferred from en.wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “Clothing Tickets Polyester Scarf” (Public Domain) via Pixabay