Browsing by Subject "Friction"

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  • An, Junxue; Liu, Xiaoyan; Dedinaite, Andra; Korchagina, Evgeniya; Winnik, Francoise M.; Claesson, Per M. (2017)
    Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force microscope colloidal probe technique. The surface forces are purely repulsive at temperatures
  • Kluger, Nicolas; Guillem, Philippe; Kivivuori, Minttu; Isoherranen, Kirsi (2020)
    Hidradenitis suppurativa (HS) is a chronic and recurrent inflammatory skin disorder affecting mainly the areas rich in apocrine sweat glands, such as the axillae, groins and buttocks. The role of mechanical pressure and friction due to clothing in the pathogenesis of HS lesions has been previously stressed. Here, we report 2 middle-aged men who presented with HS lesions/HS-like lesions on their amputation stump and review 2 additional cases from the literature. Management was challenging as 2 patients needed tumor necrosis ainhibitor while deroofing/surgery was the option for the 2 others. These cases highlight that mechanical pressure and friction are environmental factors that can play a role in the pathogenesis of HS lesions. (c) 2019 S. Karger AG, Basel
  • Lucenius, Jessica; Valle-Delgado, Juan José; Parikka, Kirsti; Österberg, Monika (2019)
    Plant-based polysaccharides (cellulose and hemicellulose) are a very interesting option for the preparation of sustainable composite materials to replace fossil plastics, but the optimum bonding mechanism between the hard and soft components is still not well known. In this work, composite films made of cellulose nanofibrils (CNF) and various modified and unmodified polysaccharides (galactoglucomannan, GGM; hydrolyzed and oxidized guar gum, GGhydHox; and guar gum grafted with polyethylene glycol, GG-g-PEG) were characterized from the nano- to macroscopic level to better understand how the interactions between the composite components at nano/microscale affect macroscopic mechanical properties, like toughness and strength. All the polysaccharides studied adsorbed well on CNF, although with different adsorption rates, as measured by quartz crystal microbalance with dissipation monitoring (QCM-D). Direct surface and friction force experiments using the colloidal probe technique revealed that the adsorbed polysaccharides provided repulsive forces–well described by a polyelectrolyte brush model – and a moderate reduction in friction between cellulose surfaces, which may prevent CNF aggregates during composite formation and, consequently, enhance the strength of dry films. High affinity for cellulose and moderate hydration were found to be important requirements for polysaccharides to improve the mechanical properties of CNF-based composites in wet conditions. The results of this work provide fundamental information on hemicellulose-cellulose interactions and can support the development of polysaccharide-based materials for different packaging and medical applications.