| Low-voltage electron beam (EB) curing is fast, efficient, solvent-free, and consequently environmentally friendly. The goal of this research is to lay the foundation for continued exploration of EB curing in general and pulsed electron beam (PEB) curing in particular.;PEB curing considerably expands the capabilities of continuous EB curing. It is significantly more versatile and speedy; yet, it requires less energy and, through appropriately timed pulses, polymerizes and crosslinks neat acrylic monomers in a single-step process. PEB exploits the inherently heterogeneous nature of energy deposition along electron tracks to spatially separate free radical initiation sites, thereby suppressing second-order termination reactions in favor of first-order propagation. This is, in effect, heterogeneous polymerization in a single phase, which is beyond the capabilities of conventional EB. Theoretical computations of conversion kinetics that include the fall of species mobility with rising conversion, which can lead to radical trapping, quantify this view of the process.;To test this model experimentally, a new PEB apparatus was constructed. It is unique in its ability to uniformly irradiate an inerted, temperature-controlled 200 cm2 sample chamber at atmospheric pressure with 80-160 kV electrons in pulses of 10-20 μsec duration at frequencies of up to 2 kHz. The flexibility of this design allows for wide-ranging investigations of PEB curing, and to ensure reliable experimental results, performance testing of the apparatus before and during experimentation established attainable voltages, pulse characteristics, and dose uniformity.;Conversion kinetics in mono- and multifunctional acrylate systems have been used to benchmark PEB curing against continuous EB and UV curing. The acrylates were converted quickly and more completely by PEB, without the need for added crosslinking agents. Observed changes in conversion with changes in operating conditions, including pulse frequency, pulse duration, dose per pulse, and temperature, were explored and are consistent with predictions from the kinetic model. These experimental results and the kinetic modeling can be applied directly to industrial web widths, and equipment design can be readily extended to large facilities.;This work also offers some alternative approaches to investigating EB curing that could prove useful. But for its versatility and low energy demand, PEB curing should be considered the future radiation curing method of choice. |
