Photorheology of Fast UV Curing Multifunctional Acrylates

The fast photopolymerization of different multifunctionalacrylates was analyzed by means of photorheology.The materials studied included a penta/hexaacrylatemonomer and two different acrylated hyperbranchedpolymers. The sensitivity of the commercial rheometer wasimproved several-fold, by a combination of an adaptive filteralgorithm and improved data treatment, using powerfuloversampling acquisition hardware. The novel set-up wascapable of monitoring up to a five orders of magnitudeincrease in shear modulus within short experiment timescales(about 10 s). The improvement in sensitivity and acquisitionrate enabled the induction time, gelation, and vitrification ofthe multifunctional acrylates to be determined. In addition,the influence of UV intensity on stiffness build-up withinthese materials was studied. In the case of the penta/hexaacrylatesystem, gelation and vitrification were detected asdistinct events, in contrast to the second-generation hyperbranchedpolyester, for which vitrification could not beidentified. These findings are related to the difference in theglass transition temperature of the cured networks. Absolute value of the complex shear modulus as a function of time for different acrylate monomers during UV curing.