Introduction to Basic Concepts of Polyurethane (Part 7)

1. What distinguishes cold-molded soft foam from hot-molded foam?
   Answer:
   ① It does not require external heat during production, significantly reducing energy consumption.
   ② High SAG factor (compression ratio), offering superior comfort.
   ③ High resilience.
   ④ Inherent flame resistance even without flame retardants.
   ⑤ Short production cycles, enabling cost savings on molds and overall expenses.
2. Characteristics and Applications of Soft and Rigid Foams

Soft Foam:

·Characteristics: The cell structure is typically open, featuring low density, excellent elasticity, sound absorption, breathability, and thermal insulation.
·Applications: Commonly used for furniture, cushioning materials, vehicle seat padding, soft laminated composites, as well as industrial and household applications like filtration, soundproofing, shock absorption, decoration, packaging, and thermal insulation.

Rigid Foam:

·Characteristics:
–Lightweight with high specific strength and good dimensional stability.
–Excellent thermal insulation properties.
–Strong adhesion.
–Long-lasting aging resistance and thermal performance.
–Good flowability of the reactive mixture, allowing it to fill complex molds or cavities.
–Highly reactive raw materials, enabling fast curing and efficient mass production in industrial settings.
·Applications:
Used as insulation materials for refrigerators, freezers, refrigerated containers, and cold storage facilities. Also applied in insulation layers for petroleum and hot water pipelines, building walls, roofs, and sandwich panels.

3. Key Considerations for Rigid Foam Formulation Design
   Polyol: High-functionality, high-hydroxyl-value (low molecular weight) polyether polyols are typically used.
   Isocyanate: The primary isocyanate for rigid foam is polymethylene polyphenyl isocyanate (commonly known as PAPI), including crude MDI and polymeric MDI.
   Blowing Agents:
   -CFCs
   -HCFCs and HFCs
   -Pentane
   -Water
   Foam Stabilizers: Block copolymers of polydimethylsiloxane and polyalkylene oxide, predominantly Si-C-based stabilizers.
   Catalysts: Mainly tertiary amines, with organic tin catalysts for specific applications.
   Other Additives: Flame retardants, cell openers, smoke suppressants, anti-aging agents, mildew inhibitors, toughening agents, and more can be included to meet specific requirements.
4. Principle of Integral Skin Foam Production
   Answer:
   Integral skin foam (ISF), also known as self-skinning foam, is a foam material that naturally forms a dense outer skin during manufacturing.