Emmanouil Chatzigiannakis

TL;DR: In this paper, the authors discuss the challenges of conducting drainage measurements at high and varied capillary numbers and how these could be overcome by the combined use of experiments and simulations, as well as how these can be combined using simulations and experiments.

TL;DR: A modified thin film balance is employed to vary the ratio of hydrodynamic to capillary stresses and its role on the dynamics of thin liquid films of polymer solutions with adequate viscosities, and it is shown how the criteria for rupture depend on the hydrod dynamic conditions, changing from stochastic to deterministic as theHydrodynamic forces inside the film damp the fluctuations.

TL;DR: This study provides new insight into the behaviour of films during bubble break-up, allows the determination of the optimum conditions for the occurrence of coalescence, and facilitates the improvement of population balance models.

Abstract: Two polyethylene types with ultra-high (UHMW-PE) and high molecular weight (HMW-PE) used as neutron radiation shielding materials in casks for radioactive waste were irradiated with doses up to 600 kGy using a 60Co gamma source. Subsequently, thermal aging at 125°C was applied for up to one year. Degradation effects in the materials were characterized using colorimetry, UV-Vis spectroscopy, IR spectroscopy, and DSC. Both materials exhibited a yellowing upon irradiation. The discoloration of UHMW-PE disappeared again after thermal aging. Therefore, the yellowing is assumed to originate from annealable color centers in the form of free radicals that are trapped in the crystalline regions of the polymer and recombine at elevated temperatures. For the antioxidant-containing HMW-PE, yellowing was observed after both irradiation and thermal aging. The color change was correlated mainly to decomposition products of the antioxidant in addition to trapped radicals as in UHMW-PE. Additionally, black spots appeared after thermal aging of HMW-PE.

TL;DR: In this article, the slip model developed by Ebrahimi et al. was used in order to relate the slip velocity, V s, to the molecular weight distribution of the polymers.