Specimens for testing were made both in laboratory and industrial settings. The parameters investigated were the effect of curing temperature (50o, 80o and 100oC studied), the effect of curing duration (0, 3 and 6 hours studied) and the effect of washing with detergent solution at 60oC (0, 2 and 4 hours studied). More limited work investigated the effect of catalyst level used. Specimens were tested for residual styrene content and for styrene migration into the appropriate EU food simulants; distilled water, 3 percent acetic acid and 15 percent ethanol. Single-sided migration cells were used with test conditions of 10 days at 40oC.
Glass-fibre reinforced plastic (GRP) vats are used in the UK in the production and storage of some food or drink, including wine, vinegar, milk, grain and grape juice, and for potable water. The unsaturated polyester resins used to make the plastic vats are cross-linked with styrene. Any styrene monomer that has not reacted completely during the curing of the resin, might migrate into a foodstuff that is subsequently stored in the vat. This report describes some systematic studies of manufacturing parameters as they affect the amount of residual styrene and its subsequent migration.
Discussions with GRP repairers had suggested that field operatives often do not or cannot follow the recommended curing procedures laid down by the polyester resin suppliers. Repairs to food contact surfaces do not lend themselves to the normal approach of taking representative samples of industrial production and sending them to a test lab. A repairer (be it of GRP vats, conveyer belts, processing equipment or food preparation surfaces) cannot test each and every repair 'in-situ' nor can they remove it to a lab for analysis. Consequently, users require recommendations along good manufacturing practice (GMP) guidelines. For these reasons, the time and temperature characteristics of GRP vat repairing need to be fully evaluated as they affect the potential for styrene migration.
The purpose of the project was therefore, to fully characterise procedures used for the repair of GRP vats resulting in data that could be used to recommend GMP guidelines.
<p>Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food
Standards Agency Research webpage</a>.