Crosslinking reactions between isocyanate compounds and acetoacetylated PVA in water and in organic solvent systems
2008
Yamada, M.(Shizuoka Univ. (Japan). Faculty of Agriculture) | Taki, K. | Shibutani, M.
The crosslinking reaction between isocyanate compounds (pMDI) and acetoacetylated PVA (AAPVA) with various degrees of acetoacetylation or partially saponified PVA were investigated in a dimethylsulfoxide (DMSO) solvent system, and compared with those in a water solvent system. The following results were obtained on the reactivity of pMDI with AAPVA and the formation of crosslinking. The crosslinking densities calculated from storage modulus (E') at the rubbery plateau regions of cured films for the DMSO solvent system were almost equal to those calculated from the temperature differences of the peak temperatures of the loss modulus (E''). However, for the water solvent system the former values were higher than the latter ones. The degree of weight swelling of cured films of pMDI and PVA for DMSO solvent systems were generally smaller than for aqueous systems. The degree of weight swelling was less for AAPVA than for pMDI and PVA. From these results, it was found that a higher crosslinking density can be attained in the DMSO solvent system rather than in the aqueous system, and that AAPVA affords higher crosslinking density than ordinary PVA.
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