The aim of this study was to determine the properties of liquid and cured UF (urea-formaldehyde) resin modified with pMDI (polymeric 4, 4'-methylenediphenyl isocyanate). Analyses showed that when introduced to liquid UF resin already at 10 %, its reactivity increases, which is reflected in a shortening of gel time and reduction of activation energy of the polycondensation process. In turn, analyses performed on polycondensed resin showed that, thanks to modification with pMDI, its hydrophobicity is considerably improved, as manifested in a reduction of absorbability and swelling in thickness of cured resin. Key words: UF, pMDI, hybrid resin, FTIR, hydrophobicity Cilj istrazivanja bio je utvrditi svojstva tekuce i otvrdnute UF smole (urea-formaldehida) modificirane s pMDI-jem (polimernim 4, 4'-metilendifenil izocijanatom). Analiza je pokazala da dodavanjem pMDI-ja tekucoj UF smoli vec u 10%-tnoj kolicini rezultira povecanjem reaktivnosti, izrazenoj skracivanjem vremena zeliranja i smanjenjem energije aktiviranja procesa polikondenzacije. Osim toga, analiza svojstava polikondenzirane smole pokazala je da je, zahvaljujuci modifikaciji s pMDI-jem, znatno poboljsana hidrofobnost, sto se ocituje smanjenjem apsorpcije i bubrenja otvrdnute smole u debljinu. Kljucne rijeci: UF, pMDI, hibridni smole, FTIR, hidrofobnost