An attempt to estimate service terms of tableware made of amino resins.

This study presents a first attempt to estimate the service terms of food contact articles made of melamine/formaldehyde and urea/formaldehyde plastics. This was achieved by following the continuous release of formaldehyde into food simulants throughout the use phase until the levels of formaldehyde migration exceeded the specific migration limit (SML), or samples were damaged and not suitable for further tests. Two test conditions were established to follow customary practices as much as possible: scenario 1, successive washing; and scenario 2, alternate courses of exposure and washing. Real melamine tableware showed conformity to the SML of formaldehyde over the course of 1500 successive washings; the estimated service term was 750 days, or about 2 years. Moreover, this service term agreed well with that found in real practice. When washing urea/formaldehyde tableware with sponges, the levels of formaldehyde migration remained below the SML, but samples eventually fractured. In the case of scrubbing pads, the levels of formaldehyde migration constantly increased and ultimately exceeded the SML. Scenario 2 resulted in accelerated migration of formaldehyde, and the SML was exceeded more rapidly than in scenario 1. Because surface roughening occurred during customary use and also during washing with scrubbing pads, it was necessary to adopt reduction factors to take into account the effects of handling when calculating service terms of articles. The results showed reduction factors ranging from 1 to 3, depending on test conditions (scenario 1 or 2) and anticipated use conditions (hot fill or use at ambient temperature). Thus, the estimated service terms of urea formaldehyde products were 117 and 175 days under hot fill and ambient conditions, respectively. These results corresponded with service terms observed in real practice, which were reported to be in the ranges of 3-4 and 6-7 months, respectively. Taking into account the time and expenses consumed during experiments, scenario 1 (successive washing with scrubbing pads) would be recommended as an appropriate method for following the migration of formaldehyde over repeated use phases and for estimating the service terms of amino-resin-based articles for food contact use.