Introduction
Foaming agents are additives used to produce cellular or foamed structures in plastic and rubber materials. During processing, these agents decompose or expand to release gases, creating a foam structure inside the material.
Foamed plastics are widely used in applications such as:
- PVC foam boards
- Artificial leather
- Rubber sponge materials
- Plastic soles and footwear
- Packaging materials
- Insulation products
Different foaming agents are used depending on the polymer type, processing temperature, and required foam structure.
Common Types of Foaming Agents
1. Azodicarbonamide (AC Blowing Agent / ADC Foaming Agent)
Azodicarbonamide (AC) is one of the most widely used chemical foaming agents.
Applications
It is suitable for a wide range of plastics, including:
- PE
- PVC
- PS
- PP
- ABS
Characteristics
- High decomposition temperature
- Produces uniform and fine foam cells
- Suitable for both closed-cell and open-cell foam structures
AC blowing agents are commonly used in:
- PVC foamed products
- Plasticized PVC paste foam
- Polyolefin calendering and molded foams
- Foamed artificial leather
2. Foaming Agent H (N,N’-Dinitrosopentamethylenetetramine)
Foaming Agent H is commonly used in rubber and plastics.
Applications
- Sponge rubber production
- PVC foaming applications
Characteristics
- Produces a large amount of gas
- High foaming efficiency
This makes it suitable for applications requiring high expansion ratios.
3. p-Toluenesulfonyl Hydrazide (TSH Foaming Agent)
TSH (p-toluenesulfonyl hydrazide) is a low-temperature foaming agent.
Applications
- PVC plastics
- Rubber products
- Closed-cell foam materials
- Sponge rubber
Important Notes
- It should not be used together with Foaming Agent H, because the reaction between the two can generate excessive heat and cause internal burning of the product.
- It should also not be used with lead-based stabilizers, as it may lead to the formation of black lead sulfide deposits.
4. OBSH Foaming Agent (4,4′-Oxydibenzenesulfonyl Hydrazide)
OBSH is a widely used foaming agent known for its versatility.
Applications
It can be used in:
- Natural rubber
- Synthetic rubber such as EPDM, SBR, CR, FKM, IIR, NBR
- Thermoplastics including PVC, PE, PS, and ABS
It is also suitable for rubber-resin composite materials.
Characteristics
- Compatible with other foaming agents
- Widely used across multiple polymer systems
Because of its broad compatibility, OBSH is often referred to as a universal foaming agent.
5. Carbonate Foaming Agents (Sodium Bicarbonate / NC Blowing Agent)
Sodium bicarbonate and modified sodium bicarbonate are examples of inorganic foaming agents.
Characteristics
- Endothermic foaming agent
- Decomposition temperature: 130–180°C
- Gas generation: approximately 125 mL/g
Applications
These foaming agents are commonly used in:
- PVC
- PS
They are particularly useful when controlled gas release and uniform foam structure are required.
6. Expandable Microsphere Foaming Agents
Expandable microspheres are special foaming materials with a core-shell structure.
Structure
- Outer shell: thermoplastic acrylic resin polymer
- Core: hydrocarbon gases (alkanes)
Characteristics
- Particle size: 10–45 microns
- When heated, microspheres can expand to several tens of times their original volume
Foaming Temperature
The expansion temperature range is approximately 75–260°C.
Applications
Expandable microspheres are mainly used in:
- Plastic footwear soles (PVC, EVA, TPU, TPE, TPR)
- Rubber foaming products
- Lightweight plastic materials
Conclusion
Foaming agents play an essential role in producing lightweight, cellular plastic and rubber products. Different foaming agents provide different advantages in terms of decomposition temperature, gas generation, foam structure, and processing compatibility.
Common foaming agents such as AC, OBSH, TSH, Foaming Agent H, carbonate foaming agents, and expandable microspheres are widely used across plastics and rubber industries to produce high-quality foamed materials.
Selecting the appropriate foaming agent depends on factors such as polymer type, processing conditions, and the desired foam structure.
