In addition, UF1 adhesive has lower values of ΔH in
regard to UF2 adhesive for all levels of catalyst content,
except for the lowest applied addition of ammonium
chloride (0.2%), at which point no significant difference
was noticed. This complex behavior of ΔH might be further
explained by the subsequent addition of monomeric
urea into the resin. Presumably, the urea addition
was higher for UF2 adhesive, which may result in the
increase of the exothermic peak of reaction, as it was
noticed in earlier research [5].