Question

In which classes, the polymers are classified on the basis of molecular forces?

Short answer

Polymers are classified into elastomers, fibers, and thermoplastics based on molecular forces.

Step-by-step solution

Understand the Concept of Molecular Forces in Polymers

Polymers are classified based on molecular forces as these forces determine the polymer's properties. The molecular forces involved here include intermolecular forces such as Van der Waals forces, hydrogen bonds, ionic bonds, and covalent bonds.

Identify Classes Based on Molecular Forces

Polymers are usually categorized into three classes on the basis of intermolecular forces: elastomers, fibers, and thermoplastics. Each class has distinct molecular force characteristics that impart different physical properties to the polymers.

Describe Elastomers

Elastomers have weak Van der Waals forces, allowing them to stretch and return to their original shape, like rubber. This elasticity is due to the polymer chains being able to slide past each other.

Discuss Fibers

Fibers possess strong intermolecular forces, including hydrogen bonds, which provide high tensile strength and rigidity. These properties make them appropriate for use in textiles and ropes.

Characterize Thermoplastics

Thermoplastics have intermediate strength in intermolecular forces, which allows them to be easily molded upon heating. They soften on heating and harden on cooling, making them versatile for manufacturing.

Key concepts

Molecular Forces

Molecular forces are the invisible connections that hold polymer chains together. They are akin to the glue that keeps the structure of a polymer intact. These forces can vary greatly in strength and type, including:

• Van der Waals forces: These are weak forces that can be easily disrupted. They occur due to temporary shifts in electron density.
• Hydrogen bonds: Stronger than Van der Waals, these occur when hydrogen atoms create a bridge between more electronegative atoms like oxygen or nitrogen.
• Ionic bonds: Strong connections resulting from the attraction between oppositely charged ions.
• Covalent bonds: The strongest type of bond, formed when atoms share electrons, forming robust connections within the polymer chain.

These molecular forces dictate the physical properties of a polymer, deciding whether a polymer is elastic, strong, or easily moldable. Understanding these forces helps in classifying polymers into different categories like elastomers, fibers, and thermoplastics.

Elastomers

Elastomers are fascinating materials known for their incredible flexibility and elasticity, characteristics rooted in their molecular structure. They contain polymer chains with weak Van der Waals forces holding them together. This weakness is advantageous, as it allows the chains to move more freely. When elastomers are stretched, the polymer chains slide past each other, but once the force is removed, they return to their original shape.
Key features of elastomers include:

• High elasticity, enabling them to stretch and recover.
• Soft and flexible texture, which makes them ideal for products like rubber bands and seals.
• Resilience, as they can endure significant deformation.

This class of polymers is primarily used in the manufacturing of goods requiring flexibility and resilience. Examples include rubber tires and various elastic materials used in everyday products.

Fibers

Fibers are strong, rigid polymers, an essential component in textiles and ropes. Their strength comes from the robust molecular forces in their structure, prominently hydrogen bonds and sometimes even ionic bonds. These forces create a closely packed alignment of polymer chains, giving fibers their high tensile strength and minimal elasticity.
Fibers are characterized by:

• Exceptional strength due to strong intermolecular forces.
• Stiffness, making them suitable for use in textiles and other durable materials.
• Low elasticity, which ensures that they maintain their shape and structure under stress.

Fibers like nylon and polyester are prevalent in creating clothes, ropes, and even fishing lines, where durability and strength are critical.

Thermoplastics

Thermoplastics are a variety of polymers distinguished by their ability to be easily molded and remolded upon heating. They have intermediate molecular force strength, mainly Van der Waals forces, which are strong enough to hold the polymer structure together but also allow flexibility upon heating.
Characteristics of thermoplastics include:

• The ability to be softened with heat and hardened when cooled, allowing them to be reshaped multiple times.
• Versatility in applications, from packaging materials to mechanical components.
• Ease of processing, making them a favorite in the manufacturing industry.

Common examples of thermoplastics include polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), and polystyrene, found in everything from piping to consumer electronics. Their ability to be different forms makes them an incredibly useful class of polymers.