Migration From polymer

An IR spectroscopy technique was developed to study the plasticiser migration from polymer compositions to the air environment. The applicability of the method was demonstrated for filled PVC compositions plasticised with di-n-butyl phthalate. Values for the effective diffusion coefficient(D) of the plasticiser were calculated from the spectroscopic data. An increase in the chalk content in a PVC composition led to a monotonic increase in D, whereas kaolin-filled compositions exhibited a more complex behaviour. The observed pattern of changes in D with varying filler content was correlated with the competing interaction of components in the system. 20 refs. (Full translation of Vys.Soed.B, 44, No.2, 2002, p.363-8)... 

Eberhardt and McCort-Tipton [23] have also applied HPLC-MS to the determination of species such as monomers, oligomers, additives and modifiers which have migrated from polymers into packaged foods. 

In the course of prolonged service life, UV absorbers are losing their absorption behavior, for example, by reaction of their phenolic function with peroxy radicals. Besides chemical reactions, simple depletion of such compounds can be another reason for the loss of their efficiency. For example, benzophenone-type UV absorbers are described to deplete from polyethylene-vinylacetate copolymer (EVA)-based encapsulants used in solar cells.In order to avoid such deficits, attempts have been made to develop UV absorbers incorporated in polymer stmctures. Manifold experimental results indicate that the loss of UV absorbers is initiated by light-induced decomposition reactions rather by migration from polymer substrates. 

Sihcone polymer plasticizers have historically been used in many formulations. These plasticizers (qv) are of the same Si—O backbone as the functional polymers but generally are terrninated with trimethyl groups which are unreactive to the cure system. This nonreactivity means that, if improperly used, the plasticizer can migrate from the sealant and stain certain substrates. Staining has been a widely pubHcized flaw of sihcone sealants, but the potential of a formulation to stain a substrate can be minimized or eliminated with proper formulation work. In general, this is accompHshed by not using plasticizers for formulations developed for stain-sensitive substrates. 

Most slabstock foams are open-celled, that is, the walls around each cell are incomplete. Towards the end of the foaming process, the polymer migrates from the membranes between cells to the cell struts, which results in a porous structure. In some cases, cells near the surface of the foam collapse to form a continuous skin, which may be trimmed off later. 

The movement of these electrons along the backbone of the polymer can be facilitated or hindered depending on the ease with which the electron can migrate from orbital to orbital. When the pz orbitals are aligned or in-plane and directly overlapping (Fig. 2, top), electron movement is facilitated. However, when the... 

Varner, S.L., Breder, C.V. and Fazio, T. (1983). Determination of styrene migration from food-contact polymers into margarine, using azeotropic distillation and headspace gas chromatography, J. Assoc. Ojf. Anal. Chem., 66, 5, 1067-1073. 

Figure 8-11 shows the proposed mechanism for isoselective propagation. Monomer coordinates at the vacant site of titanium, resulting in a four-center transition state and subsequent insertion of monomer into the polymer-transition metal bond. The insertion is referred to as migratory insertion since the polymer chain migrates from its original site to that occupied... 

Migration of PBDEs from consumer products may be a significant diffuse source of PBDEs to the atmosphere. Although no studies were found that determined the migration rate of PBDEs from polymers into the air, estimates have been calculated. Estimated migration rates for deca-, octa- and pentaBDE technical mixtures are 0.038, 0.054, and 0.39% per year, respectively (Danish EPA 1999). 

Studies of the migration of styrene monomer from HIPS and likewise from PS foams via the gas phase has been determined in a sealed system. The results show that the amount of styrene migrating from the polymers is proportional to the square root of the time of exposure (34-36). 

Ultramarines are insoluble in water and organic solvents, so the color does not bleed or migrate from paints or polymers. 

Stainless steel sieves, which can be fitted into a range of stainless steel sorbent tubes, are usually easier to handle than glass/quartz wool. It is, however, their disadvantage that some very labile compounds may degrade in contact with the metal under thermal desorption conditions. In addition, the sieves will often not completely retain the fines fraction of the used sorbents this is particularly problematic for the carbon-based sorbents, which are more brittle than the polymers and can therefore be crushed to fine particles by the thermal stress during use of a tube. The presence of a dark residue on the filters inside the thermal desorption unit is an indication of carbon-based sorbent migration from the tubes. 

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