Polyethylene films, migration

Dopico-Garcia, M.S., Lopez-Vilarino, J.M. and Gonzales-Rodriguez, M.V. (2003). Determination of antioxidant migration levels from low-density polyethylene films into food simulants, J. Chromatogr. A, 1018, 53-62. 

Physical effects caused by polyethylene glycol bases include softening and liquefaction in mixtures with phenol, tannic acid, and salicylic acid. Discoloration of sulfonamides and dithranol can also occur and sorbitol may be precipitated from mixtures. Plastics, such as polyethylene, phenolformaldehyde, polyvinyl chloride, and cellulose-ester membranes (in filters) may be softened or dissolved by polyethylene glycols. Migration of polyethylene glycol can occur from tablet film coatings, leading to interaction with core components. 

Resistance to migration of plasticizer into another polymer material. Immediate contact of plasticized polymer and another material may lead to decrease in its elasticity and in its other mechanical properties. Such changes have been found when PVC films were stored in contact with polyethylene films." Dielectric and physical-mechanical properties of the polyethylene were also degraded. These changes occurred because of plasticizer migration. The plasticizer migration rate from PVC to polyethylene decreased when plasticizer polarity increased. For example, DOS is better absorbed by polyethylene than DOP or TCP. The migration rate of plasticizer increases when the interaction between polymer... 

The situation can be much more complex if the leaching agent is a poor solvent for the additive, if it is not efficiently stirred or if the additive degrades. For example, Schwope et al. (1987) studied migration of phenolic antioxidants from low-density polyethylene films into water. They concluded that diffusion in the polymer was not the only important factor if the water was... 

Slip agents are added to polyethylene films to reduce their friction coefficient. Figure 11.17 shows that friction coefficient depends on the amount of erucamide added to LLDPE film. Increased amounts of erucamide gradually become less effective as the coefficient of friction reaches the equilibrium value characteristic of the composition. The performance of erucamide depends on the amount migrating to the surface, as Figures 11.18 and 11.19 show. The more erucamide in the polymer bulk, the higher its concentration on the film surface and the lower the coefficient of friction. 

Time of storage facilitates migration to the surface and decreases the coefficient of friction. The influence of contact with liquids and solids may remove a sufficient amount of slip agent from the surface of material to increase the coefficient of friction (see Figures 5.9, 5.10, and 7.11). Slip agent present in polyethylene used in food-contact was found to leach odorous oxidation products. Optical properties of polyethylene films were affected by several antiblocking agents but not by erucamide. ... 

Section 11.17 shows many data characterizing performance of slip agents in polyethylene film. The discussion on bulk and surface concentrations, migration to surface, distribution between layers of different composition, and the effect of these essential parameters on coefficient of friction is important for selection of additives and process design of film manufacture. 

Figures 11.17, 11.18 and 11.19 show the effect of erucamide loading and its surface concentration on static coefficient of friction of polyethylene film. Figure 10.21 shows that the winding tension also affects the coefficient of friction. At high winding tensions, slip agent does not migrate to the film surface, which contributes to increased coefficient of friction.

Castle, L., Nichol, J. and Gilbert, J. Migration of polyisobutylene additive from polyethylene films into foods during microwave and donvestic oven use. Food Additives and Contaminants, 1992, 9, 315-330,... 

Figure 4.5 Migration of labelled additives (lonox 330 o-o) from high-density polyethylene film, lonox 3300 from polystyrene film. Reproduced with permission from Figge and Koch, Food and Cosmetic Technology, 1973, 11, 4, 975 [27])...

The data in Table 13.9 indicate that, after it had migrated from the polyethylene film, lauric diethanolamide extensively hydrolysed to DEA, especially in the case of the 5% sodium carbonate and 5% citric acid extractants. Also, between 60% and 100% of the original lauric diethanolamide content of the film migrated from the film into the extraction liquid during ten days exposure at 60 °C. 

Haider,N. and Karlsson, S. (1999) Migration and release profile of Chimassorb 944 from low-density polyethylene film (LDPE) in stimulated landfills Polym. Degrad. Stab. 64, 321-328. 

Cast film extrusion is used in manufacturing polypropylene films and requires greater surface pretreatment power density (possibly 2-3 times) compared to other polyolefin films. With blown film extrusion processes, polyethylene films are typically used and require pretreatment on both sides. Considerable amounts of slip additives, used to lubricate the surface of these films for processing ease, can be prevalent within the resin and migrate to the surface of the film within a few days after extrusion. Although there is potential for the additive to mask-over treatment, it is far more important to surface treat immediately after extrusion, since it will be practically impossible to do so after additive migration to improve surface properties sufficiently for ink, coating, or lamination adhesion. 

Study of polyethylene film coextruded with ionomer film suggests that emcamide tends to migrate to more polar layer because it can be hydrogen bonded with polar polymer ... 

The proposed method of electrodialysis provides for electrolysis of a comparatively dilute solution of sodium sebacate (3,7-4.5%), and this clearly prevents oxidation of the sebacate anions in spite of the fact that platinum is recommended as anode [26], The cathode compartment of the electrodialyzer is filled with 1.07 N caustic soda, solution. The diaphragm is a cation-exchange membrane made from sulfonated polystyrene and divinylbenzene, reinforced with polyethylene film. As the sodium ions migrate from the anode to the cathode compartment the free sebacic acid, being poorly soluble, precipitates in the form of a white deposit in the anode compartment and falls to the bottom of the electrolyzer, which prevents it from being oxidized at the anode. 

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