Q34E The smoking salons of the Hinden... [FREE SOLUTION]

Chapter 31: Q34E (page 1054)

The smoking salons of the Hindenburg and other hydrogen-filled dirigibles of the 1930s were insulated with urea鈥揻ormaldehyde polymer foams. The structure of this polymer is highly cross-linked, like that of Bakelite (Section 31-6). Propose a structure.

Short Answer

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The proposed structure of thermosetting resin is:

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Thermosetting resins

Thermosetting resins refers to a petrochemical material that is irreversibly cures, because they retain their form and stay solid under heat once they are cured. Thermosetting resin becomes highly cross-linked and solidify into a hard, insoluble mass when heated.

For example, Bakelite, a thermosetting resin first produced in 1907, has been in commercial use longer than any other synthetic polymer. It is widely used for molded parts, adhesives, coatings, and even high-temperature applications such as missile nose cones.

Chemically, Bakelite is a phenolic resin, produced by reaction of phenol and formaldehyde.

Propose a structure

As the mentioned structure of the polymer is highly crossed link like a Bakelite, so it is also a phenolic resin, produced by the reaction of urea and formaldehyde.

On heating, water is eliminated, many cross-links form and the polymer sets into a rocklike mass. The cross-linking in these thermosetting resins is three-dimensional and is so extensive that we can鈥檛 really speak of polymer 鈥渃hains.