At a Glance
- Understand the labels: TDI 80/20 and TDI 65/35 identify the relative proportions of 2,4- and 2,6-TDI isomers. Confirm the supplier’s exact specification before purchase.
- Do not select by ratio alone: Neither mix is a universal best option. Selection depends on the full polyurethane formulation, process, target properties, and validation work.
- Keep flexible foam formulation-led: TDI systems are commonly associated with flexible polyurethane applications, but the approved grade must be confirmed against the actual formulation.
- Do not equate 65/35 with rigid foam: A rigid-foam requirement should trigger an isocyanate-system review. It does not automatically make TDI 65/35 the correct choice.
- Include documentation in qualification: Technical buyers should request the current SDS, specification sheet, COA requirements, traceability details, and destination-specific documents.
- Prepare a complete enquiry: State the application, preferred isomer mix, formulation status, quantity, destination, and documentation requirements before requesting commercial support.
What you’ll learn
This guide explains how to interpret TDI 80/20 and TDI 65/35 labels, which technical questions to resolve before choosing an isomer mix, and when formulation, EHS, and sourcing specialists need to be involved.
Introduction
The percentages in a TDI grade name are only the beginning of the decision. TDI 80/20 and TDI 65/35 describe isomer composition, but they do not independently determine processing behaviour, finished-polyurethane performance, or suitability for a particular foam or elastomer system.
A technical buyer should assess the mix alongside the polyol system, additives, process conditions, target properties, existing formulation status, quality documents, and site controls. The right question is not “Which TDI grade is better?” It is “Which isomer mix has been validated for the polyurethane system we are trying to make?”
How should buyers choose between TDI 80/20 and TDI 65/35?
Choose between TDI 80/20 and TDI 65/35 only after the formulation and process requirements are defined. The ratio is an important specification input, but it is not a stand-alone performance recommendation.
Start with the intended polyurethane application. Then confirm the existing or proposed polyol system, process window, target finished-material requirements, plant-validation status, documentation needs, and commercial delivery conditions. The responsible formulation team should approve the technical route before procurement treats a particular grade as interchangeable or commercially equivalent.
For rigid foam, first validate whether TDI is the appropriate isocyanate family for the system. A rigid-foam label does not automatically point to TDI 65/35. Depending on the architecture and target properties, the formulation team may need to assess another isocyanate route, including MDI-based systems.
What do TDI 80/20 and TDI 65/35 mean?
TDI refers to toluene diisocyanates, a family of reactive isocyanates that can include 2,4-TDI and 2,6-TDI isomers. Commercial TDI may be supplied as a mixture of those isomers, and the grade label indicates their relative proportions.
The 2,4-TDI and 2,6-TDI isomer concept
The 80/20 and 65/35 labels identify the relative ratio of 2,4-TDI and 2,6-TDI in a commercial material. The exact product identity, composition, and specification must still be confirmed through the supplier’s current technical documents and certificate of analysis requirements.
NIOSH TDI hazard profile identifies 2,4-TDI as toluene-2,4-diisocyanate, CAS 584-84-9, and provides workplace-hygiene context. It does not replace supplier-specific technical data, formulation review, or site EHS controls.
Why ratio alone does not determine suitability
The isomer ratio does not, by itself, tell a buyer how a system will process or what finished properties it will achieve. Reaction profile, viscosity, cure behaviour, density, hardness, durability, and other outcomes depend on the entire polyurethane formulation and operating conditions.
Treat the grade as one required specification, not as a shortcut to a finished-material result. Before a mix is approved, the formulator should assess compatibility with the polyol system, additives, process requirements, acceptance criteria, and internal validation plan.
TDI 80/20 vs TDI 65/35 comparison framework
The table below helps technical and procurement teams evaluate each offer against the same criteria. It does not declare a universal winner because grade-specific performance claims require formulation evidence and technical approval.
| Evaluation factor | TDI 80/20 | TDI 65/35 | What the buyer must verify |
| Isomer composition | Confirm on supplier specification | Confirm on supplier specification | Current specification and COA requirements |
| Intended PU system | Validate against formulation | Validate against formulation | Application and formulation fit |
| Processing behaviour | Confirm through plant trials | Confirm through plant trials | Process-validation plan |
| Polyol-system compatibility | Formulator review required | Formulator review required | Compatibility with approved polyols and additives |
| Finished-material targets | Test against acceptance criteria | Test against acceptance criteria | Property-testing protocol |
| Documentation package | SDS, specification, COA, traceability | SDS, specification, COA, traceability | Buyer and customer requirements |
| Supply and logistics | Confirm commercial route | Confirm commercial route | Packaging, destination, and handling readiness |
The important distinction is between formulation selection and procurement selection. Formulation decides whether a grade fits the intended polyurethane system. Procurement then confirms whether the supplier can provide the approved grade, documents, traceability, commercial route, and delivery terms.
For commercial context after a grade is selected, see bulk TDI sourcing guide [Bulk Toluene Diisocyanate (TDI) Supplier Guide 2026: Prices, Grades, Regulatory & Sourcing (USA)].
Flexible polyurethane foam: questions before selecting a TDI mix
Flexible polyurethane foam is a formulation family, not a single technical requirement. A buyer should not infer that a specific TDI mix is appropriate simply because a supplier or marketplace page associates it with flexible foam.
Start by determining whether the system is an existing approved formulation or a new development project. Existing systems may have a defined benchmark material and change-control process. New developments need a technical evaluation plan before procurement can establish an approved commercial requirement.
Key questions include:
- Which polyol system and additives are already specified?
- What processing criteria must be retained or achieved?
- Which finished-material properties are measured for approval?
- Is there an approved benchmark grade or supplier specification?
- What batch, COA, and traceability records are required?
- Does the site have the necessary EHS and receiving controls?
TDI selection sits within the broader polyurethane reaction system. Review polyol requirements for polyurethane systems alongside the isocyanate requirement so the co-reactant system remains part of the technical discussion.
Rigid foam: do not assume TDI 65/35 is the default choice
“Rigid foam” is not enough information to choose an isomer mix. It describes a product category, not the complete isocyanate, polyol, process, insulation, density, structural, and end-use requirement.
A responsible rigid-foam review starts with the system design. The technical team should identify the incumbent chemistry, required insulation and physical-property targets, process method, equipment, regulatory obligations, and customer acceptance criteria. Only then can the team determine whether TDI belongs in the evaluated isocyanate architecture.
MDI may be relevant to a different polyurethane route, but it is not a generic replacement recommendation. Buyers who need to broaden the technical assessment can evaluate MDI polyurethane systems with the formulation team, using the actual project requirements.
Polyurethane elastomers and CASE systems need application-specific validation
Elastomers, coatings, adhesives, and sealants, commonly grouped as CASE applications, have their own formulation constraints. A grade decision must account for the specific resin system, processing method, end-use environment, customer specification, and required performance tests.
Avoid treating either TDI 80/20 or TDI 65/35 as a standard answer for every elastomer or CASE system. Technical guidance should be supported by approved product documentation, formulation evidence, and the responsible specialist’s review.
Where the project requires a broader isocyanate evaluation, buyers can explore IPDI system requirements. This supports product discovery only. It does not mean IPDI and TDI are interchangeable.
Procurement checklist for TDI grade qualification
Once the formulation team has identified the correct technical route, procurement can create a complete grade-qualification request. This turns technical selection into a commercial enquiry that suppliers can evaluate accurately.
- Required TDI isomer mix
- Intended end use and polyurethane system
- Existing approved formulation or new-development status
- Technical specification and test criteria
- Current SDS, specification-sheet, and COA requirements
- Batch traceability and change-control needs
- Packaging and delivery location
- Storage, handling, and internal EHS readiness
- Regulatory, customer, or destination-documentation requirements
- Annual volume and per-shipment volume
This information gives suppliers a defined requirement rather than an ambiguous request for TDI. It also helps procurement compare offers that match the approved technical scope.
EHS and regulatory review belongs in every TDI sourcing decision
TDI is highly reactive, and selection should include EHS and regulatory review from the beginning. EPA TDI risk management explains the agency’s concern about workplace dermal and inhalation sensitisation and provides US stewardship context.
This article does not provide handling instructions, PPE selection, exposure-control procedures, transport guidance, or legal advice. Use the current supplier SDS, applicable requirements, site procedures, and qualified EHS professionals to assess the actual material and operation.
The commercial document package matters here as well. Before purchase approval, confirm the SDS version, specification, COA expectations, batch traceability, relevant transport information, and any customer or destination requirements.
Source TDI with the right technical and documentation inputs
A useful TDI sourcing enquiry begins after the technical selection is clear. State the proposed isomer mix, application, formulation status, target specification, expected volume, US destination, required documents, and relevant site constraints.
Elchemy acts as a B2B chemical sourcing partner, not a TDI manufacturer. Buyers with a qualified formulation can also browse industrial chemical intermediates and review North America chemical supply support before beginning a commercial discussion.
To move from grade selection to sourcing, discuss TDI sourcing requirements with the approved formulation, grade, documentation, and delivery requirements.
FAQs
1. What does TDI 80/20 mean?
TDI 80/20 indicates a commercial mixture with relative proportions of 2,4-TDI and 2,6-TDI represented by the 80/20 label. Buyers should verify the exact current composition and quality specification with the supplier. The label does not independently establish suitability for a particular polyurethane formulation.
2. What does TDI 65/35 mean?
TDI 65/35 indicates a different relative mixture of 2,4-TDI and 2,6-TDI. It is a product-identification and formulation input, not a universal performance claim. The selected mix must be assessed against the full polyurethane system, process requirements, and technical acceptance criteria.
3. Is TDI 65/35 automatically better for rigid polyurethane foam?
No. Rigid foam is not enough information to select TDI 65/35 or any other isocyanate route. The technical team should assess the entire system, including target properties, process, polyols, additives, incumbent chemistry, and validation requirements. An MDI-based or another architecture may need evaluation.
4. Can TDI 80/20 and TDI 65/35 be substituted without reformulation?
No. Treat them as distinct technical inputs. A substitution should not be made without responsible formulation review, process validation, supplier-document review, and the buyer’s change-control process. Similar names or an apparently comparable quote do not establish interchangeability.
5. What documents should a TDI buyer request from a supplier?
Request the current SDS, product specification sheet, representative COA format, traceability information, and any documents required by the destination, customer, quality system, or site EHS process. Confirm requirements before commercial approval so the documentation matches the exact material and shipment.
6. When should a buyer evaluate MDI instead of TDI?
Evaluate MDI when the polyurethane system, processing requirements, target properties, or incumbent formulation makes another isocyanate architecture relevant. This is a formulation decision, not a price-driven substitution. Use technical review to establish whether MDI, TDI, or another route should be evaluated.
Conclusion
TDI 80/20 and TDI 65/35 are isomer-mix labels, not automatic solutions for flexible foam, rigid foam, or elastomer production. A defensible selection starts with the complete polyurethane system: the polyol and additive package, required process window, finished-material targets, existing validation data, and site EHS requirements. Once the formulation team has approved the technical route, procurement can qualify suppliers against the exact grade, current SDS, specification, COA expectations, traceability, destination, and delivery terms. This separates a technical decision from a price comparison and prevents unsuitable substitutions. For an approved formulation, discuss TDI sourcing requirements.
