Blowing agents are substances used in manufacturing to create a cellular (foam) structure in materials like plastics, rubber, and metals. They work by releasing gas through physical or chemical processes, forming tiny bubbles (cells) in the base material as it solidifies, resulting in a lightweight, insulating, and often flexible product.

Types of Blowing Agents & How They Work

Physical Blowing Agents

• Mechanism: These are volatile liquids or gases that evaporate or expand due to heating or pressure drop.

• Examples: Hydrocarbons (like pentane), CO₂, HFCs (hydrofluorocarbons)

Process:

• Incorporated into the base material (e.g., plastic resin).

• When heated, they boil or expand, creating gas bubbles.

• The material sets (solidifies) around the gas, trapping the bubbles.

Chemical Blowing Agents

• Mechanism: These substances undergo a chemical reaction (often thermal decomposition) that releases gas (like N₂, CO₂, or water vapor).

Examples:

• Azodicarbonamide (ADC) – releases nitrogen gas when heated.

• Baking soda (sodium bicarbonate) – used in foamed food or biodegradable packaging.

Process:

• Mixed with the base polymer.

• When heated, they decompose and release gas.

• Foam forms as the gas disperses and gets trapped.

Key Gases Released

Applications

• Plastic foams: Polystyrene foam (Styrofoam), polyurethane insulation

• Rubber foams: Shoe soles, yoga mats

• Metal foams: Lightweight structural parts

• Food: Bread, cakes (yeast or baking soda act as blowing agents)

Summary of the Process

• Mixing: Blowing agent added to the base material (e.g., polymer resin).

• Activation: Heat or pressure change triggers gas release.

• Bubble Formation: Gas forms bubbles, expanding the material.

• Solidification: The material cures or hardens, trapping the bubbles.