The smoking salons of the Hindenburg and other hydrogen-filled dirigibles of the 1930s were insulated with urea

Question:

The smoking salons of the Hindenburg and other hydrogen-filled dirigibles of the 1930s were insulated with urea formaldehyde polymer foams. The structure of this polymer is highly cross-linked, like that of Bakelite (Section 31 .5). Propose astructure.