In June, Fusion UV Systems Inc., Gaithersburg, Md., was granted U.S. patent 6,908,586 B1, "Free Radical Polymerization Method Having Reduced Premature Termination, Apparatus for Performing the Method, and Product Formed Thereby." The patent supports the company's Light Hammer line of high intensity UV lamps for industrial UV curing. It applies to the enhanced level of curing that results when substantially constant UV is used to cure coatings and inks.

David Harbourne, president of Fusion says, "We're anticipating this can have a significant impact on existing and new UV chemistries. Some customers are already getting improved product quality and performance using the Light Hammer UV curing system."

Substantially constant UV is what differentiates this development from traditional UV lamps that use power-line AC or high-ripple DC (rectified power-line AC) to provide electrical power to the UV-emitting bulb. UV radiation with intensity that remains constant over time, without the pulses or ‘ripple' that accompanies AC or rectified AC line-synchronized lamps, produces a significant difference in the cure behavior of UV-curable materials including a higher double bond conversion rate, and a narrower molecular weight distribution, resulting in improved cure and coating properties.

The technical breakthrough that led to this patent was made by Fusion UV scientists and engineers when they realized that UV from lamps with AC or rectified AC power supplies yielded lower double bond conversion rates than with UV lamps with ripple-free DC supplies. The effect that is patented is a real photochemical effect related to the rate of production of free radicals associated with polymerization of the chemistry, improving the final result. International patent applications have been filed. For more information, visit