Sorption and diffusion of n‐alkanes into bromobutyl rubber membranes

Abstract

Sorption and diffusion of n-alkanes into bromobutyl rubber membranes were investigated in the temperature interval 25-60°C by a sorption gravimetric method. The Fickian diffusion equation was used to calculate the diffusion coefficients, which were dependent on the size of the alkanes, their interactions with the chain segments of the polymer and temperature. The diffusion coefficients varied from 0.34 x 10-'cm2/s (n-hexadecane) to 9.94 x 10-'cm2/s (n-hexane). The activation energy for diffusion varied from 14 kJ/mol (n-hexane) to 27 kJ/mol (n-hexadecane). Heat of sorption ranged from -1.4 kJ/mol for nheptane to 2.0 kJ/mol for n-hexadecane. The sorption/swelling results are discussed in terms of first and second order kinetic equations. The molar mass between chain-entanglement-crosslinks was estimated from swelling data. The experimental and calculated results showed a systematic dependence on the increasing size of the alkanes. None of the solvents showed any degradative effects on the polymer.

Polystyrene freeze-dried from dilute solution: Tg depression and residual solvent effects

“…The fact that Q N decreases with decreasing temperature indicates that the residual solvent concentration increases with decreasing annealing temperature. Assuming that the diffusivity follows an Arrhenius temperature dependence, an apparent activation energy (E a ) of 33G8 kJ/mol is obtained for the non-compacted samples, comparable to values for diffusion of small molecules in polymers [28][29][30] and also in reasonable agreement with values for diffusion of benzene in other polymers: 6-12 kJ/mol in carbon black-filled epoxidized natural rubber [31], 25-57 kJ/ mol in non-crosslinked natural rubber [32], and 95 kJ/mol in poly(ethyl acrylate) at zero solvent concentration with E a decreasing with increasing solvent concentration [33]. The activation energy is similar to the value obtained (52 kJ/mol) for recovery of the depressed T g in freeze-dried cyclic polystyrene in our previous work [5].…”

Sorption/desorption studies on polypropylene geomembrane in the presence of hazardous organic liquids

“…The values of K show a systematic increase with increasing temperature. The values of n for the present systems range between 0.50 and 0.55, suggesting the Fickian transport 11–17…”

Sorption/desorption studies on polypropylene geomembrane in the presence of hazardous organic liquids

“…The values of K represent the extent of interactions between the penetrants and the geomembrane. [11][12][13][14][15][16][17] The dimensional response of the network PP geomembrane has been studied from a calculation of the change in volume of the geomembrane due to swelling. The values of K show a systematic increase with increasing temperature.…”