ABSTRACT:The sorption of ethylene and 1-hexene and their mixture in three poly(ethylene-co-1-hexene) samples is measured gravimetrically at temperatures 70, 90, and 150°C and pressures 0 -30 bar. Gravimetric sorption measurements are supplemented with microscopic observations of swelling of polyethylene particles caused by sorption and the extent of swelling is found to be significant. Experimental data are compared with predictions of PC-SAFT (perturbed chain--statistical associating fluid theory) equation of state. Comparison of sorption data in semicrystalline polymer (measured at 70 and 90°C) and amorphous polymer (at 150°C) demonstrates the constraining effect of semicrystalline structure. Solubilities of penetrants in investigated samples are not observed to depend on the content of 1-hexene in copolymers. The solubility of the mixture of ethylene and 1-hexene is smaller than the sum of solubilities of individual components at 70 and 90°C.

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Cover: The cover image shows a 3D structure of a porous polyethylene particle reconstructed from X‐ray computed tomography images (left). Dynamic simulations of monomer degassing from reconstructed particles were carried out (upper right). Artificial particles with bidisperse granular morphology were alternatively employed in reaction and transport modeling (lower right). Further details can be found in the article by L. Seda, A. Zubov, M. Bobak, J. Kosek,* A. Kantzas on page 495.

The transport of reaction species in polyolefin particles affects both the polymerization and the degassing of the powder in the down‐stream processing. The morphology of particles – that is, the distribution of polymer and pore phases – predetermines their degassing behavior. We utilize gravimetric measurements to obtain the dynamics of degassing and to determine morphology characteristics of porous poly(propylene) particles. We found that Fick's diffusion model is not generally capable of fitting the shape of degassing curves of porous particles. Therefore we propose a particle model including two sizes of compact polymer granules and demonstrate that the degassing can be described by this model and that the model is capable of estimating fractions of large and small compact zones and the size of large compact zones.