Preparation and properties of self-crosslinkable polyurethane/silane hybrid emulsion

Self-crosslinkable polyurethane emulsion containing active carbonyl group was obtained using dihydroxyketon N-[(1,1-dimethyl-2-acetyl)ethyl]-β-dihydroxyethylamino propanamide(DDP) and 1,4-butanediol as chain extenders, isophorone diisocyanate (IPDI), polyether polyol (PTMG1000), dimethylol propionic acid (DMPA) and trimethylol propane (TMP) as main materials, γ-aminopropyltriethoxysilane (APTES) as end capping agent. Then adipic dihydrazide was added into the emulsion. The structure and composition of DDP and the films were confirmed by means of FTIR and ¹H nuclear magnetic resonance (¹H-NMR) spectrometer, the test results indicated that the reaction between ketone carbonyl and hydrazine has happened during the film curing. The effects of n(NH₂NH-)/n(C=O) and DDP content on the properties of the films were studied. The results show that water absorption of the films decreases from 39.3% to 18.9%, crosslinking degree increases from 51.5% to 90.2%, tensile strength increases from 20.1 MPa to 28.3 MPa and pencil hardness is 2H when the DDP content increases from 0% to 6.13%. TGA analysis indicates that the Ketone-Hydrazide crosslinking structure can improve thermal stability of the films.