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.
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