How to Enhance the Tensile Strength of Flexible PU Foam?

I. Molecular Chain Structure Reinforcement (Chemical Modification)

① Rigid Segment Incorporation

② Hydrogen Bond Network Optimization

Add diethanolamine (DEA):

Dosage = 0.6–0.9% of polyol mass

Promotes urethane formation, increasing H-bond density by 50%.

Introduce hydroxyethyl acrylate:

Replaces 5% of polyol; carboxyl groups form ionic crosslinks with urethane groups.

II. Precision Control of Crosslinking Structure

① Multifunctional Chain Extenders

Note: TMP >5% may increase closed cell rate and reduce rebound resilience.

② Dynamic Crosslinking Technology

Add lipoic acid derivative (0.3–0.5 wt%):

Forms reversible disulfide bonds at 60–80°C during curing, dissipating energy during stretching.

Elongation at break ↑80%, tensile strength ↑25%.

III. Reinforcement Phase Composite Technology

① Nano Dispersion System

② Microfiber Reinforcement

Add ultrafine glass fibers (diameter 3–5 μm, aspect ratio 30:1) at 1.2 wt% with silane surface treatment:

Tensile strength ↑55%, tear strength ↑90%

IV. Foaming Process Enhancement

Process Innovation:

Gradient curing:

40°C (2h) → 60°C (3h) → 80°C (3h)

Crosslink density ↑30%, internal stress ↓50%

V. Performance-Cost Tradeoff

VI. Common Problem Solutions

Cell Structure Degradation

Symptom: Reinforcing agents cause cell coalescence

Solution: Add polydimethylsiloxane (0.05–0.1 wt%) to stabilize cells

Loss of Resilience

Symptom: Higher tensile strength, lower rebound rate

Solution: Add core-shell toughening agent (e.g., ACR) at 0.8 wt%; rebound recovery >92%

Curing Yellowing

Cause: Oxidation during high-temp curing

Solution: Add hindered phenol + phosphite (ratio 2:1, total 0.3 wt%)

Validation Results:

Tensile strength ≥120 kPa

Cell uniformity: coefficient of variation ≤15% (via microscopy)

Durability: >85% strength retention after 50,000 compressions

With these strategies, tensile strength can be improved by 50%–100% while preserving slow rebound characteristics. Pre-production formulation optimization via Response Surface Methodology (RSM) is recommended to achieve the best performance-cost balance.