| 초록 |
Phenolic compounds have been used as blocking agents of isocyanate groups which show the reversible reaction, i.e. deblocking, at elevated temperature. Reversible linkages in polyurethane (PU) elastomers prepared from 4,4-methylene diphenyl diisocyanate (MDI) and poly(phenylene oxide) (PPO) diol having phenolic hydroxyl groups at both ends were investigated in this study. It was observed that the microphase separation of the PU was depressed in the PU based on PPO diol. In FT-IR spectra, we found that the isocyanate groups were generated from the PU above 140℃ by the reversible linkages formed from MDI and PPO diol. Reversibility of the linkages which generate isocyanates from the PU resulted in the decrease of melt viscosity above 140℃. It is postulated that the PU elastomers having reversible linkages show advantages of low melt viscosity for hot melt adhesives, maintaining the usual characteristics of PU elastomers. |
