The FTIR spectrum ofthe pure urea formaldehyde resin recorded
in the 4000–400 cm−1 range is reported in Fig. 4a. A broad absorption
band centered around 3378 cm−1 is related to absorbed water
in addition to the contributions from the stretching vibrations of
residual amine groups. Prominent spectral features are observed
at 1633–1560 cm−1, corresponding, to the amide I mode (mostly
C O stretching in CONH2) and the amide II mode (prevailingly
NH CO stretching). A well defined shoulder at 1712 cm−1 reflects
the multiplicity of molecular structures formed upon curing. A
strong adsorption band at 3469 cm−1 indicates hydrogen bond in
N H and OH. Few absorption frequencies are broad due to the
presence of by-products in the resin, such as water and excess
formaldehyde. This forms hydrogen bonding with the reactive
functional groups like CH2OH, NH2, and NH present in the
resin [44]. Some sharp bands are also observed because of hydrogen
bonded interaction followed by more cross linking which occurs