Food Contact Rubbers 2: Products, Migration and Regulation, Volume 16, Number 2, 2006

Chapter 4: Assessing the Safety of Rubber as a Food Contact Material

4.1 Special Considerations When Using Rubber as a Food Contact Material

The unique properties of rubber that make it such a useful material in food contact situations can also be the cause of some of its problems. The rubber matrix is lightly crosslinked and above room temperature the polymer chains are very mobile. So, unlike some of the other food contact materials (e.g., metals), the migration of low molecular weight compounds in and out of the material is relatively easy. Food can therefore penetrate into rubber and leach out the (potentially) large range of low molecular weight species within. It is possible to limit this ingress for particular applications by a careful choice of the rubber-food type combination. Although this matching process applies to the type of rubber, it is also important to take into consideration the complete rubber compound as up to 50% of a compound can be comprised of additives (e.g., plasticisers and fillers) and these can also have a profound effect on suitability and, hence, performance since if a rubber becomes swollen with the food stuff that it is in contact with a number of its important physical properties (e.g., hardness, resilience, tensile strength) will be affected. Although it is possible to make some generalisations (e.g., silicone rubber performs poorly in contact with fatty foods, and high levels of ester type plasticizers are also to be avoided with these), in common with all the other food contact materials, it is the contact conditions (time, area and...