1. What Are Polyurethane Raw Materials?
Polyurethane (PU) is one of the most versatile polymer families in industrial chemistry, used in applications ranging from flexible foam mattresses to rigid insulation panels, automotive seating, coatings, adhesives, and shoe soles.
Every polyurethane product is made by reacting two primary components:
- A polyol (containing multiple hydroxyl –OH groups)
- An isocyanate (containing –NCO groups)
When these two components react, they form urethane linkages (–NH–COO–), creating a polymer network whose properties can be precisely tuned by adjusting the type and ratio of raw materials.
The global PU raw materials market exceeded USD 80 billion in 2025 and is projected to grow at approximately 5% CAGR through 2030, driven by demand in construction insulation, electric vehicle battery encapsulation, and sustainable foam solutions.
Why Raw Material Selection Matters
The performance of the final PU product — hardness, density, flexibility, thermal resistance, chemical resistance — is almost entirely determined by the raw materials chosen. A formulator selecting the wrong polyol grade for a flexible foam application will produce foam that either collapses, becomes too rigid, or shows poor aging performance.
This guide exists to help downstream manufacturers, distributors, and procurement teams make informed decisions when sourcing PU raw materials, particularly from Chinese suppliers.
2. Polyols: Types, Properties & Selection Guide
Polyols are the "soft" component in polyurethane systems, providing flexibility, elasticity, and reactivity control. They are classified by their backbone chemistry and end-use application.
2.1 Polyether Polyols
Polyether polyols are produced by ring-opening polymerization of propylene oxide (PO) or ethylene oxide (EO) onto a starter molecule (such as glycerol, sorbitol, or water).
Key properties:
- Excellent hydrolysis resistance
- Good low-temperature flexibility
- Lower viscosity compared to polyester polyols
- Cost-effective for large-volume applications
Common grades and their applications:
| Grade | Hydroxyl Value (mg KOH/g) | MW (approx.) | Primary Application |
|---|---|---|---|
| DL-2000D (PPG-2000) | 54–58 | ~2000 | CASE applications, adhesives, elastomers |
| DEP-5631D | 28–32 | ~5600 | High-resilience (HR) flexible foam, furniture |
| DEP-3500D | 45–50 | ~3500 | Memory foam, mattresses |
| EP-330N(G) | 33–37 | ~5000 | High-resilience molded foam, automotive seating |
When to choose polyether polyol:
- Applications requiring moisture resistance (outdoor foam, marine applications)
- Cold-climate applications requiring low-temperature flexibility
- Cost-sensitive high-volume foam production
2.2 Polyester Polyols
Polyester polyols are produced by condensation of diols with dicarboxylic acids. They offer superior mechanical strength and oil resistance compared to polyether polyols, but are more susceptible to hydrolysis.
Key applications: PU elastomers, synthetic leather (PU coating), rigid structural foam, CPU (cast polyurethane) wheels and rollers.
DOBO's polyester-based products: DB-HC-6300 Series Polyester CPU Elastomer Prepolymer — a ready-to-use prepolymer system for elastomer casting applications.
2.3 Specialty Polyols
Graft polyols (SAN polyols):
- Contain dispersed solid particles for enhanced load-bearing capacity in flexible foam
Flame-retardant polyols:
- Incorporate phosphorus or halogen groups for building insulation applications meeting fire standards
Bio-based polyols:
- Derived from castor oil, soybean oil, or sucrose for sustainable formulations
2.4 How to Select a Polyol — Decision Checklist
Ask these questions before specifying a polyol:
- What is the end product? (Flexible slabstock foam / molded foam / rigid foam / elastomer / coating / adhesive)
- What hardness/density is required? Higher hydroxyl value → stiffer, denser product
- What are the environmental exposure conditions? (Humidity, temperature extremes, UV exposure)
- What processing equipment is available? (High-pressure vs. low-pressure mixing machines have different viscosity requirements)
- What certifications are required? (REACH, RoHS, OEKO-TEX for textile applications)
3. Isocyanates: MDI vs TDI — Complete Comparison
Isocyanates are the reactive "hard" component in polyurethane systems, providing mechanical strength and chemical resistance. The two dominant commercial isocyanates are MDI (Methylene Diphenyl Diisocyanate) and TDI (Toluene Diisocyanate).
3.1 MDI — Methylene Diphenyl Diisocyanate
MDI exists in several commercial forms:
Polymeric MDI (PMDI) — CAS 9016-87-9
The most widely used form of MDI. PMDI is a dark brown liquid with NCO content of 30.5–32.0% and functionality of 2.6–2.9, making it ideal for rigid foam systems where a highly crosslinked network is desired.
| Parameter | Specification |
|---|---|
| CAS Number | 9016-87-9 |
| NCO Content | 30.5–32.0% |
| Viscosity at 25°C | 150–250 mPa·s |
| Functionality | 2.6–2.9 |
| Density at 25°C | 1.22–1.25 g/cm³ |
| Appearance | Dark brown liquid |
Primary applications of PMDI:
- Rigid PU foam insulation panels (cold storage, building insulation)
- Spray polyurethane foam (SPF) roofing and wall insulation
- Wood binders and particle board adhesives
- Structural insulated panels (SIPs)
Liquefied MDI (MDI-50 / Modified MDI) — CAS 26447-40-5
Modified MDI with reduced functionality, designed to remain liquid at room temperature. Used in elastomers, adhesives, and flexible systems where pure MDI's crystallization tendency is problematic.
Leading brand equivalents: Wanhua PM200, BASF Lupranate M20S, Huntsman Suprasec 5005, Covestro Desmodur 44V20L.
3.2 TDI — Toluene Diisocyanate (CAS 584-84-9)
TDI 80/20 is the standard commercial grade, consisting of 80% 2,4-TDI isomer and 20% 2,6-TDI isomer. Its bifunctionality (f=2) and higher reactivity make it the preferred choice for flexible foam.
| Parameter | Specification |
|---|---|
| CAS Number | 584-84-9 |
| Isomer Ratio | 80:20 (2,4-TDI : 2,6-TDI) |
| NCO Content | 48.2–48.6% |
| Viscosity at 25°C | 3–4 mPa·s |
| Density at 25°C | 1.22 g/cm³ |
| Appearance | Colorless to pale yellow liquid |
Primary applications of TDI 80/20:
- Flexible slabstock foam (mattresses, furniture cushions)
- Molded flexible foam (automotive seats, headrests)
- Waterborne PU coatings and adhesives
- PU elastomers (shoe soles, industrial rollers)
3.3 MDI vs TDI — Side-by-Side Comparison
| Criteria | MDI (PMDI) | TDI 80/20 |
|---|---|---|
| Vapor pressure | Very low (safer handling) | Higher (requires ventilation) |
| Functionality | 2.6–2.9 (polymeric) | 2.0 (bifunctional) |
| Reactivity control | More controllable | Higher reactivity, shorter demolding |
| Foam type | Rigid foam preferred | Flexible foam preferred |
| Cost | Generally lower per kg | Slightly higher |
| Key application | Insulation panels, spray foam | Mattresses, furniture, automotive |
| Wanhua brand | PM200 | TDI 80/20 |
| BASF brand | Lupranate M20S | Lupranat T80 |
Rule of thumb: If your end product needs to be rigid and thermally insulating → choose MDI. If your end product needs to be flexible and elastic → choose TDI.
4. Specialty Isocyanates: HDI, HMDI
4.1 HDI — Hexamethylene Diisocyanate (CAS 822-06-0)
HDI is an aliphatic diisocyanate, meaning its NCO groups are not attached to an aromatic ring. This makes it non-yellowing under UV exposure — a critical property for exterior coatings and automotive clearcoats.
Applications: Automotive topcoats, outdoor industrial coatings, UV-stable PU coatings, waterborne PU dispersions.
Note: HDI is classified as DG Class 6.1 (toxic). Requires proper DG shipping certification and documentation.
4.2 HMDI — Hydrogenated MDI (CAS 5124-30-1)
HMDI (also called H12MDI or Desmodur W) is produced by hydrogenating MDI to remove the aromatic rings, yielding an aliphatic isocyanate with exceptional weathering resistance and optical clarity.
Applications: High-end automotive refinish coatings, optical-grade PU lenses, medical-grade PU films, premium synthetic leather topcoats.
When to choose aliphatic vs aromatic isocyanates:
- Exterior or UV-exposed applications → HMDI or HDI (aliphatic)
- Interior or non-yellowing-critical applications → MDI or TDI (aromatic, lower cost)
5. PU Additives: Catalysts, Surfactants & Blowing Agents
The reaction between polyol and isocyanate is accelerated and controlled by a suite of additives that determine foam structure, reactivity profile, and final properties.
5.1 Amine Catalysts
Amine catalysts accelerate the urethane reaction (polyol + isocyanate) and/or the blowing reaction (isocyanate + water → CO₂).
- A33 (Dabco 33-LV equivalent): Triethylenediamine in dipropylene glycol. Strong gel catalyst.
- A1 (Niax A-1 equivalent): Strong blowing catalyst for slabstock foam.
- BDMAEE: Delayed-action catalyst for better flowability in rigid foam.
5.2 Organotin Catalysts
Organotin compounds (DBTDL, T-12) are strong gel catalysts used in CASE applications, coatings, and elastomers. Restricted in some EU applications due to environmental regulations — always check REACH compliance requirements.
5.3 Silicone Surfactants
Silicone surfactants (L-580 equivalent, B-8462 equivalent) stabilize the rising foam and control cell size. Cell structure uniformity directly affects foam density uniformity and mechanical properties.
5.4 Blowing Agents
| Blowing Agent | Type | Notes |
|---|---|---|
| Water | Chemical (reacts with NCO to generate CO₂) | Most common; increases foam hardness |
| HFCs (R-134a, R-245fa) | Physical | Phase-out under Kigali Amendment |
| HFOs (1233zd, 1336mzz) | Physical | Low GWP replacement for HFCs |
| HCFC-141b | Physical | Banned in developed countries, still used in some markets |
| Cyclopentane | Physical | Standard for refrigerator insulation |
6. Plasticizers for PU Applications
Plasticizers are not polyurethane raw materials per se, but they are widely used alongside PU systems to modify flexibility, reduce cost, and improve processing. DOBO Chemical supplies a complete range of plasticizers that are commonly co-purchased with PU raw materials.
6.1 Phthalate Plasticizers
| Product | CAS | Application | REACH Status |
|---|---|---|---|
| DOTP (Dioctyl Terephthalate) | 6422-86-2 | PVC, cable PVC replacement | Not on the SVHC Candidate List |
| DINP (Diisononyl Phthalate) | 28553-12-0 | General PVC, flooring | Not SVHC listed |
| DOP (Dioctyl Phthalate) | 117-81-7 | General purpose | SVHC listed, restricted in EU |
| DPHP | 53306-54-0 | High-temperature PVC | Not on the SVHC Candidate List |
6.2 Non-Phthalate Plasticizers
- ESBO (Epoxidized Soybean Oil, CAS 8013-07-8): Bio-based co-plasticizer and heat stabilizer for PVC
- EFAME (Epoxy Fatty Acid Methyl Ester): Eco-friendly alternative to ESBO, increasingly used in food-contact applications
- DOA (Dioctyl Adipate, CAS 123-79-5): Low-temperature flexibility, cold-resistant PVC
- TOTM (Trioctyl Trimellitate, CAS 3319-31-1): High-temperature applications, automotive cables, wire insulation
Regulatory note for EU buyers: Under REACH, several phthalates (DEHP, DBP, BBP, DIBP) are classified as SVHC substances and require authorization for use in EU-produced articles. DOBO recommends DOTP or DINP as compliant alternatives.
7. How to Select the Right PU Raw Materials for Your Application
Use this application-based selection matrix:
Flexible Slabstock Foam (Mattresses, Furniture)
- Polyol: DEP-5631D (HR polyether, HV 28–32) or DEP-3500D (memory foam, HV 45–50)
- Isocyanate: TDI 80/20 (CAS 584-84-9)
- Index: 105–115 (slightly over-indexed for durability)
- Key additives: Silicone surfactant (L-580), A33 catalyst, water as blowing agent
Rigid Insulation Foam (Building, Cold Chain)
- Polyol: Rigid foam blended polyol system (combination polyol, pre-blended)
- Isocyanate: PM200 PMDI (CAS 9016-87-9), index 110–120
- Key additives: Cyclopentane or HFO blowing agent, amine + potassium catalyst
- Note: Rigid foam requires higher isocyanate index and lower polyol OH value
PU Shoe Soles & Footwear System
- Prepolymer: DB-DXD-3280A/3118B (safety sole) or DB-EXD-3070A/3022B (sandal sole)
- Processing: Two-component casting system, 50–60°C mold temperature
- Key property targets: Shore A 40–65, split tear strength >6 N/mm
Spray Polyurea / Waterproofing
- Prepolymer: DB-8310 spray polyurea waterproofing prepolymer
- Application: Roof waterproofing, underground structures, bridge deck coatings
- Processing: Plural-component spray equipment, 1:1 volume ratio
CASE (Coatings, Adhesives, Sealants, Elastomers)
- Polyol: DL-2000D CASE polyether diol (MW ~2000, HV 54–58)
- Isocyanate: MDI-50 (liquefied MDI) for ambient-cure systems; HMDI for non-yellowing exterior systems
- Key consideration: Moisture sensitivity — all components must be kept dry
8. Sourcing PU Raw Materials from China: Step-by-Step Guide
China accounts for over 60% of global polyether polyol production capacity and is the world's largest exporter of TDI, MDI, and related PU chemicals. Understanding how to source efficiently and safely from Chinese suppliers is critical for international buyers.
Step 1: Define Your Requirements
Before contacting any supplier, prepare a sourcing specification document including:
- Product name and CAS number
- Required technical parameters (OH value, NCO content, viscosity, purity)
- Required certifications (REACH, RoHS, SGS, COA/TDS/MSDS)
- Quantity: annual volume in metric tons or FCL (20ft container)
- Packaging preference: 200KG drums / 1000KG IBC totes / 23MT flexitank
- Destination port and incoterms (FOB Ningbo, CIF Rotterdam, DDP, etc.)
Step 2: Evaluate Supplier Qualifications
Key supplier qualification checklist:
- ISO 9001:2015 certified (factory level)
- Ability to provide COA (Certificate of Analysis) for each batch
- TDS (Technical Data Sheet) and MSDS (Material Safety Data Sheet) available
- REACH compliance documentation (SVHC declaration, SDS per REACH Annex II)
- Experience with DG (Dangerous Goods) shipping — MDI, TDI, and HDI are classified DG
- References from buyers in your region
Step 3: Request Samples Before Bulk Order
For any new PU raw material supplier, always request a 5–25 kg sample before placing a commercial order. Key tests to perform on samples:
- Hydroxyl value / NCO content (titrimetric analysis)
- Viscosity at 25°C (Brookfield viscometer)
- Water content (Karl Fischer titration — critical for isocyanates)
- Color (APHA scale for polyols, visual for isocyanates)
- Foam trial (run a small-scale formulation test)
Step 4: Understand DG Shipping Requirements
Most PU raw materials are classified as Dangerous Goods:
| Product | UN Number | DG Class | Packing Group |
|---|---|---|---|
| TDI 80/20 | UN 2078 | 6.1 (Toxic) | II |
| PMDI (MDI) | UN 2489 | 6.1 (Toxic) | III |
| HDI | UN 2290 | 6.1 (Toxic) | III |
| Propylene Oxide | UN 1280 | 3 (Flammable) | II |
DOBO Chemical handles all DG documentation and has established logistics partnerships with freight forwarders experienced in chemical cargo.
Step 5: Typical Lead Times and Container Sizes
- Standard lead time: 7–15 business days after order confirmation
- 20ft container capacity: ~20–23 MT (flexitank) or ~100 drums (200KG each)
- Minimum order quantity: Negotiable; trial orders from 1 drum (200KG) available
- Common incoterms: FOB Ningbo Port, CFR, CIF, DDP (customs clearance included)
9. Quality Standards, Testing & Compliance
ISO 9001:2015
All of DOBO Chemical's partner manufacturing facilities maintain ISO 9001:2015 quality management system certification. This ensures consistent production processes, batch traceability, and documented quality control procedures.
REACH Compliance
The EU Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) regulation (EC No 1907/2006) applies to all chemicals imported into the EU in quantities exceeding 1 tonne per year per importer.
Key requirements for PU raw material imports into the EU:
- SVHC substances (Substances of Very High Concern) above 0.1% w/w must be disclosed
- Safety Data Sheet (SDS) must comply with REACH Annex II format in the local language
- Pre-registration / registration may be required for volumes >1 tonne/year
DOBO provides Safety Data Sheets that meet REACH Annex II requirements for the products we export, and can supply EU REACH registration information for applicable substances on request.
RoHS Compliance
The EU RoHS Directive restricts certain hazardous substances in electrical and electronic equipment (EEE). For PU components used in EEE applications (e.g., cable insulation, encapsulation of electronic components), RoHS compliance documentation is required.
SGS Third-Party Testing
DOBO offers SGS third-party testing as an optional service. SGS certificates provide independent verification of product specifications and are accepted by most international buyers as evidence of quality.
10. Pricing, MOQ & Logistics Guide
Price Ranges (Reference, Subject to Market Fluctuation)
| Product | Typical Range (USD/MT, FOB China) | Notes |
|---|---|---|
| Polyether Polyol (standard grades) | USD 1,100–1,600/MT | Varies with PO feedstock price |
| PMDI (PM200 grade) | USD 1,400–1,900/MT | Wanhua spot price reference |
| TDI 80/20 | USD 1,500–2,100/MT | Highly volatile, tracks toluene price |
| HDI | USD 4,500–6,500/MT | Premium aliphatic isocyanate |
| HMDI | USD 8,000–12,000/MT | Specialty grade, limited suppliers |
| DOTP | USD 900–1,200/MT | Stable, non-SVHC status drives demand |
Note: Prices are indicative and subject to feedstock costs, seasonal demand, and logistics conditions. Request current pricing via the inquiry form.
MOQ (Minimum Order Quantity)
DOBO Chemical offers flexible MOQ to accommodate both trial and commercial orders:
- Trial / sample: 1 drum (200KG) or 1 IBC tote (1000KG)
- Commercial: 1 FCL (approximately 20–23 MT for bulk liquid, or 100 × 200KG drums)
- Annual contract pricing: Available for buyers committing to 3+ FCL per year
Estimated Shipping Transit Times
| Destination | Sea Freight (FCL) | Notes |
|---|---|---|
| Southeast Asia | 5–12 days | Singapore, Vietnam, Thailand, Indonesia |
| Middle East | 18–25 days | UAE, Saudi Arabia, Turkey |
| Europe | 28–38 days | Rotterdam, Hamburg, Felixstowe |
| South America | 30–45 days | Santos, Buenos Aires |
| East Africa | 20–30 days | Mombasa, Dar es Salaam |
| North America | 18–30 days | Los Angeles, Houston |