Adhesive vs. Cohesive

Attribute	Adhesive	Cohesive
Definition	Substance used for sticking objects together	Ability of a substance to stick to itself
Examples	Glue, tape, stickers	Water droplets on a leaf
Function	Joining two different surfaces	Keeping similar particles together
Surface	Sticks to other surfaces	Sticks to itself

Definition

Adhesive and cohesive are two terms that are often used interchangeably, but they actually have distinct meanings in the world of materials science. Adhesive refers to a substance that is used to stick two surfaces together, while cohesive refers to the internal strength of a material that holds it together. In simpler terms, adhesive is what sticks things together, while cohesive is what keeps a material intact.

Function

Adhesives are commonly used in a wide range of applications, from household repairs to industrial manufacturing. They are designed to create a bond between two surfaces, providing strength and stability. Cohesive forces, on the other hand, are responsible for holding the molecules of a material together. This internal strength is crucial for maintaining the integrity of the material, especially under stress or pressure.

Types

There are various types of adhesives available, each with its own unique properties and applications. Some common types include epoxy, super glue, and hot melt adhesives. These adhesives can be used on a variety of materials, such as metal, plastic, and wood. Cohesive forces, on the other hand, are present in all materials to some extent. However, certain materials, such as metals and ceramics, have stronger cohesive forces than others.

Strength

Adhesives are known for their bonding strength, which can vary depending on the type of adhesive used and the surfaces being bonded. Some adhesives are designed to provide a temporary bond, while others offer a permanent bond that is difficult to break. Cohesive strength, on the other hand, is a measure of how well a material can resist being pulled apart. This strength is determined by the material's molecular structure and the forces holding the molecules together.

Flexibility

Adhesives are often chosen for their flexibility, as they can be used to bond materials that may expand or contract. This flexibility allows for movement without compromising the bond. Cohesive materials, on the other hand, may not be as flexible, depending on their molecular structure. Some materials are more rigid and less able to withstand movement without breaking.

Durability

When it comes to durability, adhesives can vary greatly depending on the type and application. Some adhesives are designed to withstand extreme temperatures, moisture, and other environmental factors. Cohesive materials, on the other hand, are inherently durable due to their strong internal bonds. These materials are less likely to break or degrade over time, making them ideal for long-lasting applications.

Applications

Adhesives are used in a wide range of applications, from simple household repairs to complex industrial processes. They are commonly used in woodworking, construction, and automotive industries. Cohesive materials, on the other hand, are found in everyday objects such as glass, metal, and ceramics. These materials rely on their internal strength to maintain their shape and integrity.

Conclusion

In conclusion, adhesive and cohesive are two important concepts in the world of materials science. While adhesives are used to bond surfaces together, cohesive forces are responsible for holding materials together internally. Both play a crucial role in the strength, flexibility, and durability of materials. Understanding the differences between adhesive and cohesive can help in choosing the right materials for a specific application.