1. Why TDI Still Dominates Flexible Foam (and What to Look For)

Flexible polyurethane (PU) foam — the material in mattresses, sofa cushions, automotive seats, and packaging — is most commonly made by reacting a polyether polyol with toluene diisocyanate (TDI) in the presence of water (chemical blowing agent), amine and tin catalysts, silicone surfactant, and optional flame retardants.

TDI's dominance comes from its unique differential reactivity: the 2,4-TDI isomer has one fast (para) and one slower (ortho) —NCO group, which lets the foam rise and gel in a controlled sequence. MDI-based systems exist (for high-resilience and molded foams), but TDI remains the cost-performance leader for conventional slabstock flexible foam.

If you are sourcing TDI for flexible polyurethane foam production, the decision is not just "buy TDI" — it is buying the right isomer grade, the right acidity/chloride spec, and a supplier whose batch-to-batch consistency protects your line uptime.

2. The TDI Grades Used in Flexible Foam

For 90 %+ of flexible foam producers — especially those running continuous slabstock bunkers — TDI 80/20 is the default specification. This guide focuses on TDI 80/20, with notes on when TDI 65/35 enters the picture.

3. TDI 80/20 Specifications for Foam Manufacturing

Below is the reference specification range drawn from major producer TDS documents (Hanwha KONNATE T-80, Dow VORANATE T-80, BASF). Use it as a baseline for your purchase specification; the supplier's current COA governs each shipment.

3.1 Product identity

3.2 Quality specification (buy this, not just "TDI")

3.3 Typical flexible slabstock foam formulation reference

This is a starting point — your polyol system, catalyst package, and target density will drive the actual numbers.

Typical processing times on a continuous bunker: cream 8–15 s, rise 60–120 s, gel 90–180 s.

4. Selecting the Right TDI Grade for Your Foam Product

4.1 Match grade to foam type

4.2 Type I vs Type II acidity — choose by your line, not by price

· Type I (low acidity, ≤15 ppm HCl, ≤40 ppm hydrolyzable Cl): faster reaction, more catalyst-active. Best for high-speed continuous slabstock where line throughput drives economics.

· Type II (controlled acidity, ~80–100 ppm HCl): deliberately retarded. Best for pour-in-place, slow-rise systems, or wide buns where you need more flow time before gel.

· Do not swap without re-catalyzing. A Type II TDI in a Type I formulation will under-rise and collapse; a Type I in a Type II system will gel prematurely and split.

4.3 When to consider TDI 65/35 instead

If your foam needs higher resilience, better compression set, or softer hand-feel (premium mattresses, automotive comfort), TDI 65/35 — with its higher 2,6-TDI fraction — gives a more flexible polymer network. It freezes at ~5 °C, so it handles more easily in winter than T-100, but it is a smaller-volume grade and may carry a price premium.

5. Supplier Evaluation: What "Industrial TDI Supplier" Should Actually Mean

For a foam plant, a TDI supplier is only as good as batch consistency and logistics. Evaluate on these criteria:

5.1 Documentation per shipment

· Certificate of Analysis (COA) showing every parameter in §3.2 — not just purity. Reject suppliers that only state "TDI 80/20, 99.5 % min."

· Safety Data Sheet (SDS) current to GHS / REACH format.

· MSDS / transport documentation for UN 2078 (Class 6.1, packing group II).

5.2 Regulatory compliance by destination

· China domestic: GB/T standard, factory production license.

· Sea freight: IMDG-classified packaging, UN-approved drums or tank containers.

5.3 Packaging options

5.4 Quality consistency questions to ask

· What is the batch-to-batch range of 2,4-TDI % and acidity? (You want tight control, not just spec minima.)

· Can the supplier provide COAs from the last 3 shipments for review?

· What is the origin producer? (Major producers have tighter internal specs than blenders/traders.)

· What is the typical shelf life from manufacture date to your arrival?

· What is the minimum order quantity (MOQ) for drums vs tank containers?

5.5 Logistics and storage on your side

· TDI 80/20 freezes at ~12 °C. In winter, confirm cold-chain or heated container shipping if transit may go below 12 °C. Frozen TDI is recoverable (warm to 20–30 °C, homogenize), but delayed.

· Store sealed under dry nitrogen blanketing at 15–30 °C. Moisture ingress = CO₂ pressure buildup and ruined product.

· Use dedicated, dry pumping equipment; never reuse water-contaminated drums.

6. Red Flags in a TDI Quote