Additive diffusion from LDPE slabs into contacting solvents as a function of solvent absorption

Abstract

This article describes the simultaneous diffusion of a migrant and a solvent in low density polyethylene (LDPE). The migrant (Irganox 1076) moves out of the slab, while the solvent (isooctane, n-heptane or cyclohexane) moves inwards. Solvent absorption was measured separately by following the increase of the mass of the slab in time. It can be described by the Fick diffusion equation with a diffusivity depending on the solvent concentration, and an interface concentration depending on time. The final absorptions were 12% for isooctane, 14% for n-heptane, and 29%for cyclohexane. Additive concentrations in the slab were determined at different positions by microtoming. Experiments were done for several contacting times. The concentration profiles were strongly affected by the solvent. A larger local solvent concentration increases the diffusivity of the migrant. The Fick equation with a migrant diffusivity depending on the solvent concentration gives a good description for the results with isooctane and n-heptane. The description is less good for the measurements with cyclohexane (when the polymer swells strongly).

Stabiliser diffusion in long-term pressure tested polypropylene pipes analysed by IR microscopy

“…This allows the calculation and fitting of spatial concentration profiles leading to more precise diffusion coefficients [26]. A time saving alternative is the analytical calculation of constant diffusion coefficients: The lateral concentration of Irganox 1010 is averaged over the pipe wall and these values are plotted against the testing time.…”

Influence of polymer swelling and dissolution into food simulants on the release of graphene nanoplates and carbon nanotubes from poly(lactic) acid and polypropylene composite films

“…()] arise. The diffusion of compounds dissolved at the interface between the polymer and the solvent is often described by an empirical equation relating the diffusion coefficient with the solvent concentation: where D P (cm 2 /s) is the diffusion coefficient of migrant in the polymer at zero solvent concentration, (mg/cm 3 ) is the concentration of food simulant solvent, and is an adjustable parameter.…”

Determination of mass transport properties in food/packaging systems by local measurement with Raman microspectroscopy

“…Because KPL data is scarce and because of the time required to reach equilibrium for high‐barrier polymers, the determination of D in the latter is made difficult. As consequence, most published D values have been collected for polymers that are rubbery at room temperature . Rare D values exist for the two high‐barrier polymers most used in the packaging industry [polystyrene (PS) and poly(ethylene terephthalate)], and they are often for low‐ to medium‐molecular‐weight and presumably highly volatile molecules.…”

“…As consequence, most published D values have been collected for polymers that are rubbery at room temperature. [4][5][6][7][8][9][10][11] Rare D values exist for the two high-barrier polymers most used in the packaging industry [polystyrene (PS) and poly(ethylene terephthalate)], and they are often for low-to medium-molecular-weight and presumably highly volatile molecules. In the case of amorphous PS, reported D values concern cyclohexane (86.2 g/mol); 12 linear alkanes (from 114.3 to 226.4 g/mol); 13 carboxylic acids (from 60.1 to 256.4 g/mol); 14 alcohols (from 32 to 242.4 g/mol); 15 toluene (92.4 g/mol), chlorobenzene (112.6 g/mol), and phenyl cyclohexane (160.26 g/mol); 16 homologous series of fluorescent tracers (from 230 to 1120 g/mol); 17 and Rubrene (532.7 g/mol), 18 with the majority of values being determined in the rubbery state.…”