Migration, additives Antioxidants

Marcato, B., Guerra, S., Vianello, M. and Scalia, S. (2003). Migration of antioxidant additives from various polyolefinic plastics into oleaginous vehicles, Int. J. Pharm., 257, 217-225. 

Goydan, R., Schwope A. D., Reid R.C., and Cramer G., 1990, High temperature Migration of Antioxidants from Polyolefins. Food Additives and Contaminants 1,323-337. 

Rybak, K.E. Sarzynski, W. Dawidowicz, A.L. Migration of antioxidant additives from pol3qjropylene investigated by means of reversed phase high performance liquid chromatography. Chem. Anal. 1992, 37, 149-159. 

The name of the resin material, the name and address of the manufacturer, the chemical name, the complete formulation, characteristics and quantity of all ingredients and the function are required where the material is to be used in a container which will be exposed very intimately to the product, such as a large volume parenteral solution or eye drop. The identity, using IR absorption along with a reference spectrum must be provided. Additives, particularly those likely to migrate, including antioxidants, plasticisers, catalysts, initiators and materials such as phthalates, adipates and organic tin in PVC or any dyes used in the resin must also be identified. 

Antioxidants play an important role in the deceleration of lipid oxidation reactions in foodstuffs. According to FDA they are defined as substances used as preservatives, with the aim to reduce spoilage, rancidity or food discoloration, which are derived from oxidations. Addition of antioxidants in foodstuffs is either intentional (direct addition into product) or symptomatic (migration of antioxidants from packaging material into product). The right and effective use of antioxidants depends on the understanding of (a) the chemistry of oils and fats, and (b) the mechanism of oxidation and their operation as substances, which result in food oxidation (Table 13.12). ... 

An effective way to modify polymer properties is to add low molecular weight additives such as fillers, antioxidants, and plasticizers. This is also done in the polymer industry to obtain more precise properties and to broaden the application field. Every system must be optimized since there are many different additives to choose between and the chemical nature of the additives influences the film morphology, pol)mier crystallinity and desired mechanical properties, as well as the degradation processes. It is important also to remember that the additives should not be too volatile because this could cause evaporation during processing. In addition, it is crucial that migration is limited and controlled since the migrating additives, such as plasticizers, can cause contamination of materials in contact with the plasticized PLA. 

Additives such as antioxidants and photostabilizers of low-molecular weight face two major problems (1) they may evaporate during high temperature moulding and extrusion process or (2) they may migrate to the surface of the plastic and get extracted. There are, in general, three ways of overcoming these problems. 

Compounds for use as antioxidants have to fulfil a number of requirements in addition to their effectiveness in stabilising the polymer. For example, they must have low toxicity and be inexpensive. They must also be fully compatible with the polymer of choice since otherwise they tend to migrate to the surface where they impart an unacceptable appearance. Any such migration also depletes the concentration in the bulk which leads to a loss of protection for the polymer. 

The solubility of wax in vulcanised rubbers is low (of the order of 0.5% for NR) but enough wax has to be added to a rubber compound to ensure that once the compound has been vulcanised and the rubber cools, the rate of migrational movement of the wax from the rubber mass to the surface of the rubber is rapid. Dependant upon the application, the addition level of wax can be up to about 10 phr. Migration of the wax to the rubber surface will also carry other ingredients such as antioxidants, antiozonants and other materials (e.g., vulcanisation residuals), to enhance the surface protection. 

---