Workhorse With the Goods

According to Dickenscheidt, this is important for two main reasons: time and application. “Cationic formulations were originally used almost exclusively because they tend to give a slower cure so that your adhesive will start very tacky and then harden after setting for a period of time. Free radical mechanisms always cure in about half a second to a given degree of tackiness. The primary advantage of free radicals is that the process has more leeway since the adhesive will stay at a certain level of tackiness after curing, allowing you to apply your label, etc., at any time,” he said. “Cationic adhesives must be applied and allowed to set at very precise dwell times. Also the cationic process is affected by humidity, so that dwell times will change as the humidity goes up or down. Cationic adhesives are still useful for applications requiring a stronger bond between substrates, however, the adhesive will dry to a very hard film instead of remaining soft like the free radical adhesives. The selection of mechanisms is based on end-product requirements, as well as ease of processing and humidity control.”