- Characteristics of Horizontal and Vertical Foaming
Answer:
Horizontal Foaming:
Edge Film Lifting Method: Enhances traditional horizontal foaming by introducing a side traction mechanism that synchronizes edge and central foam rise, yielding nearly flat-topped foam blocks.
Balanced Press Plate Method: Uses top paper and a top cover plate to achieve balance.
Overflow Trough Method: Employs overflow troughs and conveyor descent plates for production.
Vertical Foaming:
Achieves large cross-sectional foam blocks with smaller material flow, requiring 3–5 times less flow than horizontal foaming for equivalent block size.
Produces foam with thinner skins and no upper or lower surface skins, significantly reducing cutting losses.
Requires minimal floor space, with factory height at approximately 12–13 meters, resulting in lower facility and equipment costs compared to horizontal methods.
Offers flexibility to produce cylindrical or rectangular foam blocks, including round blocks for rotary cutting, by switching hoppers and molds.
- Key Criteria for Soft Foam Raw Material Selection
Answer:
Polyols:
Common polyether polyols for general foam blocks have a molecular weight of 3000–4000, mainly using triol-based polyethers. High-resilience foams use polyethers with molecular weights of 4500–6000. Higher molecular weights improve tensile strength, elongation, and resilience but reduce reaction activity. Increased polyether functionality accelerates reactions, raises cross-link density, enhances foam hardness, and lowers elongation.
Isocyanates:
TDI-80 (toluene diisocyanate) is the primary isocyanate for polyurethane soft foam blocks, while TDI-65, with lower activity, is limited to polyester foams or specific polyether foams.
Catalysts:
Soft foam catalysts are divided into organic metal compounds (e.g., stannous octoate) and tertiary amines (e.g., bis(dimethylaminoethyl) ether).
Foam Stabilizers:
Non-silicone surfactants dominate polyester foam, while silicone-olefin copolymers are widely used in polyether-based foams.
Blowing Agents:
Water is used exclusively for foam densities above 21 kg/m³. In low-density formulations, low-boiling compounds like methylene chloride (MC) act as auxiliary agents.
- Environmental Impact on Foam Properties
Answer:
Temperature: Rising material temperatures accelerate foaming reactions, potentially causing core burning or fire hazards in sensitive formulations.
Humidity: Higher humidity decreases foam hardness and increases elongation due to isocyanate reacting with ambient moisture. Urea group formation enhances tensile strength.
Atmospheric Pressure: At higher altitudes, foam density significantly decreases under the same formulation conditions.
- Key Differences Between Cold-Cured and Hot-Cured Soft Foam Systems
Answer:
Cold-Cured Foams: Use high-activity raw materials that rely on self-generated heat for curing, completing the process quickly and enabling demolding within minutes.
Hot-Cured Foams: Utilize lower-activity raw materials, requiring external heat post-foaming for full curing within molds or ovens before demolding.
