Migration Polymer additives

Uvitex OB 5 0.05 Optical density at 378 nm due to Uvitex OB is less than 3% of the optical density due to interference at 378 nm by all the other migrated polymer additives present. Uvitex cannot be determined under these conditions. 

The methods of analysis of polymer additives and chemicals, such as hydrocarbons, alcohols, etc., are not only restricted to the field of polymer chemistry but can also be applied for the analysis of such materials in the field of food chemistry. In addition, the analysis of polyaromatic hydrocarbons in edible oils has been of extreme importance. Polymeric packaging materials that are intended for food-contact use may contain certain additives that can migrate into the food products which are actually packaged in such products. The amounts of the additives that are permitted to migrate into food samples are controlled by government agencies in order to show... 

Applications Applications of UV/VIS spectrophotometry can be found in the areas of extraction monitoring and control, migration and blooming, polymer impregnation, in-polymer analysis, polymer melts, polymer-bound additives, purity determinations, colour body analysis and microscopy. Most samples measured with UV/VIS spectroscopy are in solution. However, in comparison to IR spectroscopy additive analysis in the UV/VIS range plays only a minor role as only a limited class of compounds exhibits specific absorption bands in the UV range with an intensity proportional to the additive concentration. Characteristic UV absorption bands of various common polymer additives are given in Scheirs [24],... 

The process of migration of additives or contaminants from polymeric food packaging to food may be separated into three stages diffusion within the polymer, solvation at the polymer food interface, and dispersion into bulk food. 

Now, in the case of Xj Xj then the polymer additive i will be overrun by the simulant before it can migrate out of the polymer. Depending on the solubility of the simulant in the polymer (KPj value), the migration behaviour of i will then be influenced in an accelerated way. In the case, however, that Xi Xj then the migration of i from the plastic is not influenced by the migration of the simulant. 

O Brien A., Cooper I., (2002), Practical experience in the use of additive models to predict migration of additives from food contact polymers. Food Additives and Contaminants, 19, pp 56-62. 

The control of EOF is critical to the migration time precision of the separation. Among the factors affecting the EOF are buffer pH, buffer concentration, buffer viscosity, temperature, organic modifiers, cationic surfactants or protonated amines, polymer additives, field strength, and the nature of the capillary surface. 

Berg, B.E. Hegna, D.R. Orlien, N. Greibrokk, T. Determination of low levels of polymer additives migrating from polypropylene to food simulated liquids by capillary SFC and solvent venting injection. Chromatographia 1993, 37, 271-276. 

Diffusion and migration of additives from the polymer matrix into a surface may have both accelerating or stabilizing effects. 

Long-term properties of polymers are severely affected and the service-life is reduced due to the migration of additives. There is also the possibility that some of the additives accumulate in the environment and affect our health and the environment. SPME has been applied for the extraction of several common polymer additives. Since additives often have rather low volatility, a significant advantage with SPME and HS-SPME compared to HS-GC-MS is the ability to extract even semi-volatile compounds [9,13]. 

Further on, a wide variety of esters were detected containing specific molecular moieties characterizing man made chemicals. E.g. the 2-ethylhexyl group represents a molecular substructure frequently used in the technosphere dominantly as the corresponding alcohol or acid, but the natural occurrence of this molecular moiety is very scarce. Thus, the detected 2-hydroxypropylester of 2-ethylhexanoic acid represents a specific anthropogenic contaminant. The fro-propyl and butyl esters identified also reflect mainly the emission of technical contaminants chiefly derived from migration processes of polymer additives. 

Additives are incorporated by the resin manufacturer and/or by the packaging processor. The presence of additives in packaging applications raises the question of additive migration. Most additives diffuse within the polymer and often tend to migrate to the surface of the material. When a packaged product is in direct contact with a compounded polymer, there may be a transfer of the additive to the product. (Of course, it is also possible for components of the product to be transferred to the polymer.) The extent of transfer depends on a series of conditions, and is discussed in Chapter 13. We will briefly examine compounding, and then discuss some common additives used in packaging. 

Identification of polymers is a complex process. Additives change the physical properties of polymers and their presence may confuse the results of tests to examine flexibility, hardness and density. Degradation of polymers changes their physical and chemical properties compared with new materials. Degraded polymers are often stiffer and darker than new materials, which is likely to confuse identification based on appearance. Their surfaces may become tacky due to migration of additives or disrupted by the formation of cracks. 

On the other hand, there are also studies showing the effects of UV irradiation on the change of migration characteristics of the matrix polymer, (i.e., effect on the migration of phthalate ester plasticisers from clear PET water bottles [87]), and some data are provided on the effects of ionising irradiation on polymer additives, monomers and polymers themselves in general [88]. 

The first test results after 28 days of storage under water already show a reduction of chloride migration coefficients for the mortars with polymer additives (Fig. 4). When compared to the reference mortar composition, a reduction in the chloride-migration-coefficient from 1.55x10-12 mVs to 0.80x10-12 mVs was achieved, by using styrene-acrylate of 20 % concentration. 

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