Why formulators are evaluating bio-based diisocyanates

Polyurethane formulators are increasingly reviewing the raw materials used in coatings, adhesives, elastomers and prepolymers. In addition to mechanical performance and processing behavior, teams may need to consider bio-based content, appearance retention, viscosity and compatibility with an existing formulation process.

DDI, or dimer acid diisocyanate, is a bio-based diisocyanate identified by CAS 68239-06-5. Its non-yellowing profile makes it a candidate for applications where color stability and long-term appearance are important. As with any raw material change, the final result depends on the complete formulation, process conditions and curing system.

DDI product profile

The current product reference data for DDI includes:

• CAS Number: 68239-06-5
• Molecular formula: C38H70N2O2
• Relative molecular mass: approximately 600
• NCO content: 13.6-15%
• Viscosity: less than 150 mPa.s at 20 C
• Density: 0.924 g/cm3
• Hydrolyzable chlorine: no more than 0.05%
• Moisture: no more than 0.1%
• Flash point: 296 C
• Appearance: yellow transparent oily liquid

These values are provided as a product reference. Buyers should confirm the applicable specification, test method and batch documentation for their intended use before production adoption.

Application areas

Polyurethane coatings

DDI can be evaluated in polyurethane coating systems where non-yellowing behavior, flexibility and appearance are important. Formulators should review compatibility with the selected polyol, catalyst, solvent or reactive diluent, as well as the required curing conditions. Small-scale testing is recommended before changing a commercial formulation.

Polyurethane adhesives

For adhesives, the key review points may include substrate adhesion, open time, cure speed, flexibility, moisture resistance and storage stability. DDI can be considered as part of a broader formulation study rather than as a drop-in replacement with identical behavior in every system.

Polyurethane elastomers

Elastomer developers can assess DDI in relation to hardness, tensile properties, elongation, resilience and low-temperature flexibility. The influence of the soft segment, chain extender, catalyst and curing schedule should be evaluated together with the diisocyanate selection.

Polyurethane prepolymers

DDI may also be considered for polyurethane prepolymers. During development, teams should pay attention to NCO balance, viscosity control, moisture exposure, pot life and the reactivity of the complete system. Processing conditions should be established through laboratory and pilot-scale trials.

What to check before selecting a supplier

1. Whether the proposed specification matches the formulation target.
2. Whether the supplier can provide consistent batch documentation.
3. Whether packaging, storage and handling instructions are suitable for the intended logistics route.
4. Whether the supplier can support sample evaluation and technical communication.
5. Whether the regulatory status is appropriate for the destination market. For the current product information, REACH registration status should be confirmed with the supplier; the present public wording is REACH registration in progress.

A practical evaluation approach

A structured evaluation can begin with a laboratory batch using the buyer's own polyol and curing system. The test plan may include appearance, viscosity, cure behavior, adhesion or mechanical properties, depending on the final application. Results should be compared with the incumbent material under the same test conditions so that any performance difference can be identified clearly.

DDI is best evaluated as part of the complete polyurethane system. The suitable use level, processing window and final performance should be confirmed by the formulator through application testing.

Discuss your formulation requirements

Henan Nayu New Materials Co., Ltd. provides DDI for technical evaluation in coatings, adhesives, elastomers and polyurethane prepolymers. If you are assessing a bio-based diisocyanate, please contact our team with your application, target properties and test requirements. We can then discuss the appropriate technical information and evaluation process.