Isocyanates

Isocyanates (Component A) are very reactive chemicals. Isocyanates react with polyols (Component B) to make polyurethanes, but they also can react with many other things. For example, isocyanates will react with water or even water vapor in the air. Similar to a package of bread that is left open and becomes stale, isocyanates left in an open container will change as they react with any moisture, including moisture in the air. This can have a negative effect on the manufacturing process and the quality of the finished polyurethane part.

Isocyanates can also react with themselves under extremely hot or extremely cold temperatures. Again, this can have a negative effect on the manufacturing process, so isocyanates should always be stored at the temperatures recommended by the manufacturer.

Finally, isocyanates will react with human tissue, such as skin, eyes and the respiratory tract, including the lungs. For this reason, you should always wear proper, recommended protective equipment and avoid breathing isocyanate vapors. Before working with isocyanates and polyurethanes in general, you must understand how to properly store and handle them. Bayer offers its customers extensive materials and training in the safe storage and handling of its polyurethane products through its BayCare(SM) Progressive Product Stewardship program.

Most isocyanates are supplied in a liquid form at room temperature, but depending on the type of isocyanate, it may be a solid at room temperature.

Isocyanates come in many types. Two of the most commonly used isocyanates are MDI (diphenylmethane diisocyanate) and TDI (toluene diisocyanate). Different types of isocyanates can have very different properties. Bayer's isocyanate products include Mondur® and Desmodur® isocyanates.

In general terms, MDI is used to produce semi-rigid and rigid polyurethane foams for products like polyurethane insulation, molded polyurethane foams for uses like the soles of footwear, and polyurethane adhesives, coatings and elastomers.

TDI is most commonly used to make flexible polyurethane foams, such as those used as furniture cushions and mattresses.