What Is Plastic Foam?
Plastic foam refers to molded synthetic resins containing air bubbles, resulting in porous materials with numerous independent and continuous pores, akin to the structure of charcoal and pumice stone.
The primary synthetic resin materials used for plastic foam production include polyurethane, polystyrene, and polyolefin, collectively known as the “three major foamed plastics.” Foamed plastics derived from polystyrene are commonly referred to as styrene foam.
Industrial methods for forming air bubbles in plastic foam include direct gas mixing into the synthetic resin material and the use of foaming agents such as sodium bicarbonate, which are mixed into the resin material beforehand and activated by heat to induce foaming and bubble formation.
Uses of Plastic Foam
Plastic foam finds versatile applications due to its excellent cushioning, heat insulation, and buoyancy properties, making it suitable for various products and components across different industries.
1. Transportation and Packaging Materials for Agricultural and Marine Products
Plastic foam serves as transportation and packaging material for agricultural and marine products, offering exceptional shock absorption, heat insulation, and lightweight characteristics. Polystyrene foam sheets (PSP) and polystyrene bead foam (EPS) are commonly used in packaging containers for fresh produce and seafood due to their thermal insulation properties.
2. Automotive Components
Plastic foam is utilized in automotive components to enhance safety by providing shock absorption and reducing overall vehicle weight. Urethane foam and polypropylene resin (PP) are commonly used in automotive seat cushions, mattresses, and bumpers due to their softness, resilience, impact resistance, and cost-effectiveness.
3. Heat Insulator for Building Materials
Plastic foam serves as a building material for its excellent thermal insulation properties. Types such as beaded polystyrene foam, extruded polystyrene foam, rigid polyurethane foam, and phenolic foam are used in construction for their heat insulation effectiveness. These foams are also known for their moldability and flame retardancy.
Features of Plastic Foam
Pros
- Lightweight compared to solids of equivalent volume
- Excellent cushioning, thermal insulation, and buoyancy properties
- Can enhance the functionality of non-foamed molded products
Cons
- Inferior strength and heat resistance compared to solid materials
- The large volume makes transportation in bulk challenging
- Contributes to environmental pollution as plastic waste
How to Select Plastic Foam
The properties of plastic foam vary based on the synthetic resin type and bubble structure. Select foam type based on application requirements, considering factors such as heat resistance and bubble structure (independent or continuous).
How to Use Plastic Foam
Pre-molded plastic foam products can be directly utilized, while foam sheets can be shaped using molding machines. Ongoing research explores composite materials involving plastic foam and other substances to enhance strength.
Other Information on Plastic Foam
Foam Molding Methods for Foamed Plastics
1. Melt and Foam Molding Method
This technique involves mixing a blowing agent with molten resin to induce foaming. It is commonly used for thermoplastic resins like polystyrene and polyolefins.
2. Solid-Phase Foam Molding Method
Solid-phase foam molding produces foam from solid resin particles, used in products like EPS and EPP for fish boxes and automotive parts.
3. Injection Molding
Injection molding involves injecting liquid resin into a mold and foaming during curing, employed for polyurethane and phenolic foam production.