What is the Difference Between MDI and TDI?
🆚 Go to Comparative Table 🆚MDI (methylenediphenyl diisocyanate) and TDI (toluene diisocyanate) are both man-made chemicals used in the production of polyurethane materials, but they have some differences in their properties and applications. Here are the key differences between MDI and TDI:
- Isocyanate content: TDI has a higher isocyanate content (48.3%) than MDI (33.6%), which results in a larger foaming volume per unit mass for TDI.
- Toxicity: MDI is less toxic than TDI. MDI has a low vapor pressure, is not easy to volatilize, has no irritating odor, and is less toxic to humans, while TDI has a high vapor pressure, is easy to volatilize, and has a strong pungent odor.
- Curing speed: The MDI system has a faster curing speed compared to the TDI system. MDI-based foam generally needs only 1 hour to achieve 95% maturity, while TDI-based foam requires 12-24 hours to achieve the best performance.
- Foam density: MDI is easier to develop diversified foam products with high relative density. By changing the proportion of components, it can produce products with a wide range of hardness.
- Applications: MDI is mainly used for the production of rigid polyurethane foams, while TDI is mainly used for the production of flexible polyurethane foams. TDI offers better high-temperature resistance and performance, better compression set, and is a good option for applications with repetitive or sustained compression, such as gaskets and bumpers. In contrast, MDI delivers excellent performance at lower temperatures, offers stronger rebound, and better heat dispersal, making it suitable for applications with extreme cold temperatures, such as gaskets in industrial settings.
Comparative Table: MDI vs TDI
MDI and TDI are two types of diisocyanates used in the production of polyurethane materials. They have different properties and applications. Here is a table comparing their differences:
| Property | MDI (Methylenediphenyl Diisocyanate) | TDI (Toluene Diisocyanate) |
|---|---|---|
| Chemical Structure | Two benzene rings with 33.6% isocyanate group content | One benzene ring with 48.3% isocyanate group content |
| Color and Form | Light yellow crystalline solid | Clear, colorless to pale yellow liquid |
| Toxicity | Less toxic, low vapor pressure, no irritating odor | Highly toxic, high vapor pressure, strong pungent odor |
| Foaming Volume | Lower foaming volume per unit mass | Higher foaming volume per unit mass |
| Curing Speed | Faster curing speed, short molding cycle | Slower curing speed, longer molding cycle |
| Environmental Protection and Safety | Better environmental protection and safety | Lower production cost but higher isocyanate content |
| Applications | Rigid polyurethane foams, coatings, adhesives | Elastomers for furniture, mattresses, footwear, packaging |
MDI is less toxic and has a faster curing speed compared to TDI. It is also more expensive to produce but offers better environmental protection and safety. On the other hand, TDI has a higher isocyanate content and is slightly less expensive to produce. When selecting a polyurethane system, manufacturers should consider product performance, environmental requirements, and budgetary constraints to develop the most suitable product.