Preparation and properties of UV-curable polyurethane methacrylate cationomers and their use as adhesives

Cationomeric polyurethanes (containing methacrylic functionality) were prepared from a diisocyanate [toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI)], polyethylene glycol (PEG 200, PEG 400, or PEG 1000), 2-hydroxyethyl methacrylate (HEMA), N-methyldiethanolamine (N-MDEA), and dimethyl sulfate (DMS), using dibutyltin dilaurate (DBTDL) as a catalyst. The ultraviolet (UV) curable aqueous cationomeric emulsions were then made with these reactive polyurethane oligomers (having hydrophilic groups), water, and photoinitiator [1-(4-isopropylphenyl)-2-hydroxy-2-methyl propane-1-one]. The effects of PEG chain length and different diisocyanates on properties of the emulsions were studied. The effect of concentration of cationomers on the thermal stability of these systems was also studied. These emulsion systems were evaluated as adhesives before and after curing under UV light. With decrease in PEC molecular weight, the glass transition temperature of the polymers increased and the storage modulus, tensile strength, and peel strength also increased. but the percentage of elongation decreased, Polymer containing TDI was found to have the highest glass transition temperature, storage modulus, peel strength, and tensile strength when compared to the polymer containing HDI or IPDI.