Mono and Multifunctional Maleimides as Photoinitiators in UV Curing Formulations

Maleimides as photoinitiators of acrylate polymensation are considered. The optimisation of cure conditions reveal that H bulbs, nitrogen inerting and use of tertiary amine synergists dramatically improve the photoinitiating efficiency of maleimides.
Optimisation of the chemical structure reveals that aliphatic maleimides with a methylene group attached to the imidic nitrogen exhibit the greatest photoinitiating efficiency.
A new synthetic route for preparation of mono and multifinctional maleimides via a maleimide acid chloride synthon is described. Mono and multifunctional maleimides prepared via this new route were evaluated. The studies reveal that maleimides are less yellowing and give less photoinitiator based extractables when compared with conventional Type I and Type II photoinitiators. Use of aliphatic maleimides under the optimum cure conditions (i.e with amine synergist and nitrogen inerting) can give rise to maleimide photoinitiated polymensation /cure that is comparable or faster than conventional Type II arvi carbonyl .