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Bis-maleimides with different substituents were synthesized and the photo-curability was studied using the monitoring conversion, gel fraction and real-time DRA. The monitoring of conversion was tried using UV absorption spectra instead of IR or Raman spectroscopy and the conversion of bis-maleimides could be followed successfully. The non-substituted bis-maleimide reacted the most rapidly and di-substituted did the worst, which could be explained by not only steric factor of substituents but also the inactivation of radical polymerization for
di-substituted maleimides. Mono-substituent behaved between the others. The reactivity of the maleimide with urethane bond was more rapidly than without urethane, although the main structure and concentration of the functional group were the same. The enhanced photo-curability of maleimide with urethane bond could be caused from either acceleration by the gel effect or localization of maleimide group by neighboring urethane group participation. Polyester-based bis-maleimide gave an excellent peel adhesion like a solvent-base conventional PSA although the viscosity became higher than PPG-based. The mono-substituted maleimides brought the sufficient holding power and SAFT. The cured adhesive was odorless expectantly, since photoinitiator, monomer and solvent were not contained at all.
