Difference Between Rubbers and Plastics - Key Properties Explained

Properties, Structure & Uses

Rubbers and plastics are both polymers, but they have distinct properties that make them suitable for different applications. While rubbers (elastomers) are known for their elasticity, plastics are more rigid and moldable. This article explores the key differences between rubbers and plastics, including their intermolecular forces, structure, and real-world uses.

Quick Summary:

• Rubbers (Elastomers): Highly elastic, weak intermolecular forces, used in tires, seals, and flexible products.
• Plastics: Rigid or semi-flexible, stronger intermolecular forces, used in packaging, bottles, and durable goods.

1. What Are Rubbers and Plastics?

Rubbers (Elastomers)

Rubbers are elastic polymers that can stretch and return to their original shape when force is removed. They can be natural (like latex rubber) or synthetic (such as silicone and neoprene).

Plastics

Plastics are synthetic polymers that can be molded into solid objects. They are categorized into thermoplastics (can be remelted, e.g., polyethylene) and thermosets (irreversibly harden, e.g., epoxy).

2. Key Differences Between Rubbers and Plastics

Property	Rubbers (Elastomers)	Plastics
Elasticity	Highly elastic (stretches and recovers)	Less elastic (rigid or semi-flexible)
Intermolecular Forces	Weak van der Waals forces (allows stretching)	Stronger forces (hydrogen bonds, covalent cross-links)
Structure	Amorphous with coiled chains	Amorphous or semi-crystalline
Deformation	Reversible (returns to shape)	Mostly irreversible (except thermoplastics)
Applications	Tires, seals, shoe soles	Bottles, packaging, automotive parts

3. Differences Based on Intermolecular Forces

Rubbers (Elastomers)

• Weak van der Waals forces allow polymer chains to slide and stretch.
• Light cross-linking (e.g., vulcanization) prevents permanent deformation.
• Remains flexible at room temperature due to low glass transition temperature (Tg).

Plastics

• Thermoplastics (e.g., PE, PVC) have weaker forces (van der Waals, dipole-dipole) and can be remelted.
• Thermosets (e.g., Bakelite) have strong covalent cross-links, making them rigid and heat-resistant.

4. Conclusion: Which One Should You Choose?

Rubbers are ideal for applications requiring flexibility and elasticity (e.g., tires, gaskets). Plastics are better for rigid, moldable products (e.g., containers, automotive parts). The key difference lies in their molecular structure and intermolecular forces.

Further Reading: Types of Polymers | Thermoplastics vs Thermosets

5. Frequently Asked Questions (FAQs)

Q1: Can rubber be considered a type of plastic?

No. While both are polymers, rubbers have elastic properties due to weak intermolecular forces, whereas plastics are generally more rigid.

Q2: Which is more environmentally friendly: rubber or plastic?

Natural rubber is biodegradable, but synthetic rubber and most plastics are not. Biodegradable plastics (like PLA) are emerging as eco-friendly alternatives.

Q3: Why does rubber stretch more than plastic?

Rubber has coiled polymer chains with weak van der Waals forces, allowing stretching. Plastics have stronger bonds, restricting movement.