Basic Concept Q&A on Polyurethane(Part Nine)

1. What are the characteristics of cold-molded soft foam compared to hot-molded foam?

Answer:

No external heat is needed during production, saving a significant amount of thermal energy.

High sag factor (compression set), providing good comfort performance.

High rebound rate.

The foam has some inherent flame-retardant properties even without added flame retardants.

Short production cycle, which can save molds and reduce costs.

2. Characteristics and uses of soft foam and rigid foam

Answer:

Soft Foam Characteristics: The cell structure of polyurethane soft foam is mostly open-cell. It generally has low density, good elastic recovery, sound absorption, breathability, and thermal insulation properties.

Uses: Mainly used as furniture padding, seat cushions for vehicles, various soft padding laminated composite materials. Industrial and civilian uses include filtration materials, soundproofing materials, shock-absorbing materials, decorative materials, packaging materials, and thermal insulation materials.

Rigid Foam Characteristics: Polyurethane foam is lightweight, has high specific strength, and good dimensional stability. Polyurethane rigid foam has excellent thermal insulation properties, strong adhesion, good aging performance, long thermal insulation service life, and the reactive mixture has good fluidity, allowing it to fill complex mold cavities or spaces smoothly. The raw materials used for polyurethane rigid foam have high reactivity, enabling rapid curing and efficient, large-scale production in factories.

Uses: Used as insulation materials for refrigerators, freezers, refrigerated containers, cold storage, petroleum pipelines, and hot water pipelines, insulation for building walls and roofs, insulated sandwich panels, etc.

3. Key points in designing a rigid foam formulation

Answer:

Polyol: The polyether polyols used in rigid foam formulations are generally high-functionality, high hydroxyl value (low molecular weight) polyoxypropylene polyols.

Isocyanate: The isocyanates currently used for rigid foam are mainly polymethylene polyphenyl isocyanate (commonly known as PAPI), i.e., crude MDI, polymeric MDI.

Blowing Agents:

CFC blowing agents

HCFC and HFC blowing agents

Pentane blowing agents

Water

Foam Stabilizers: Foam stabilizers used in polyurethane rigid foam formulations are generally block copolymers of polydimethylsiloxane and polyoxyalkylene, with most current stabilizers being Si-C type.

Catalysts: Catalysts for rigid foam formulations are mainly tertiary amines, with organotin catalysts used in special circumstances.

Other Additives: Depending on the different uses and requirements of polyurethane rigid foam products, other additives such as flame retardants, open-cell agents, smoke suppressants, antioxidants, antifungal agents, toughening agents, etc., can also be added to the formulation.

4. Preparation principle of integral skin foam

Answer:

Integral skin foam (ISF), also known as self-skinning foam, is foam plastic that forms a dense skin layer on its own during manufacturing.