TDI (Toluene Diisocyanate)
TDI is a commonly used raw material for polyurethane, mainly applied in flexible foams, elastomers, and coatings . Its chemical structure gives it high reactivity, allowing it to readily react with polyols to form polyurethane. However, TDI also has several drawbacks during production and usage, such as yellowing , toxic gas emissions , and thermal decomposition at high temperatures .
- Performance: Polyurethane made from TDI exhibits good elasticity and softness , making it suitable for flexible foams and elastomers . Due to its high reactivity, TDI is less ideal for applications requiring high strength and hardness.
- Cost: TDI has a relatively low raw material cost , making it a more cost-effective choice for polyurethane production.
MDI (Methylene Diphenyl Diisocyanate)
Compared to TDI, MDI has higher reactivity and better thermal stability . Polyurethane made from MDI has greater strength, hardness, and wear resistance , and is widely used in rigid foams, elastomers, and adhesives . However, it also has some disadvantages, such as tendency to crystallize and toxic emissions during use and processing.
- Performance: MDI-based polyurethane shows excellent strength, hardness, and abrasion resistance , suitable for rigid foams and high-performance elastomers . It also provides better thermal resistance and reactivity than TDI-based polyurethane.
- Cost: MDI is generally more expensive than TDI, resulting in higher production costs for MDI-based polyurethane.
NDI (Naphthalene Diisocyanate)
NDI is a newer polyurethane raw material with high reactivity and excellent thermal performance . Polyurethane derived from NDI demonstrates outstanding strength, hardness, and abrasion resistance , making it ideal for high-performance applications such as engineering plastics and specialty elastomers . However, NDI also faces challenges such as higher production costs and crystallization issues .
- Performance: NDI-based polyurethane offers superior strength, hardness, and durability , making it suitable for engineering-grade polyurethane and specialized elastomers . Compared to TDI and MDI, NDI-based polyurethane has better thermal resistance and dimensional stability .
- Cost: NDI is currently more expensive than both TDI and MDI, but as production technology advances and industrial-scale manufacturing becomes more widespread, NDI costs are expected to gradually decrease.