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Presents research on switchable tackiness and wettability of liquid crystalline polymer. Effects of temperature changes on the spreading velocity of liquids on the surface of a liquid crystalline polymer; Change from a rigid to a soft behavior, with consequent effects on the tack properties on the liquid crystalline polymer and on the dewetting dynamics of a liquid on its surface.

Biodegradable plastics appear as one promising means to help solving the increasing issue of environmental pollution by plastics. The present study aims at comparing the biodegradation mechanisms of two promising biodegradable plastics, PHBV Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and PBSA Poly(butylene succinate-co-adipate) with the objective to provide a better understanding of the mechanisms involved and identify the most relevant indicators to follow biodegradation. For this purpose, the progress of the biodegradation process was monitored under controlled composting conditions at the laboratory scale at 58 °C using several methodological approaches for evaluating polymer degradation. Indicators of the extent of material disappearance based on respirometry and mass loss measurements were combined to other indicators evidencing the morphological, structural and chemical modifications induced at the surface or in the bulk of the material as surface erosion by SEM, decrease of molecular weight by GPC, crystallinity changes by DSC and chemical changes by ATR-FTIR. As expected, both polymers were rapidly biodegraded in less than 80 days. However, in spite of its higher molecular weight and degree of crystallinity, PHBV degraded faster than PBSA, which led to suggest that different biodegradation mechanisms would be involved. At this regard, a two-phase scenario was proposed for each polymer on the strength of all the degradation-induced changes observed at the polymer surface and in its bulk. Based on these two scenarios, the discrepancy in biodegradation rate between PHBV and PBSA would be essentially attributed to significant differences in crystals morphology and spatial organization of both polymers. Regarding the relevance of the different indicators studied, mass loss stood out as the most relevant and accurate indicator to assess the disappearance of material especially when combined with respirometry and mineralization kinetics assessment. Besides, indicators focusing on the surface changes as SEM, AFM and POM were emphasized since seen as powerful tools to evidence morphological changes at different scales. At last, changes in thermal properties as crystallinity rate and melting temperature, even if complex to interpret due to the wide range of interdependent mechanisms they bring into play appeared as inescapable tools for improving the understanding of the underlying mechanisms involved in polymer biodegradation. • Biodegradation mechanisms of PHBV and PBSA compared in lab-scale composting conditions. • Complementary methodological approaches used for evaluating PHBV and PBSA degradation. • Degradation-induced changes monitored at the polymer surface and in its bulk. • PHBV and PBSA displayed significant differences in crystals morphology and spatial organization. • A two-phase scenarios was proposed for explaining differences in PHBV and PBSA degradation. [ABSTRACT FROM AUTHOR]

• - Biodegradable plastics are relevant for selected applications. • - Better certification and clearer instructions are needed to improve waste management. • - Methodological limits hamper the evaluation of plastic biodegradability and toxicity. • - Considering the environment as a waste treatment system is not acceptable. This opinion paper offers a scientific view on the current debate of the place of biodegradable plastics as part of the solution to deal with the growing plastic pollution in the world's soil, aquatic, and marine compartments. Based on the current scientific literature, we focus on the current limits to prove plastic biodegradability and to assess the toxicity of commercially used biobased and biodegradable plastics in natural environments. We also discuss the relevance of biodegradable plastics for selected applications with respect to their use and end of life. In particular, we underlined that there is no universal biodegradability of plastics in any ecosystem, that considering the environment as a waste treatment system is not acceptable, and that the use of compostable plastics requires adaptation of existing organic waste collection and treatment channels. [ABSTRACT FROM AUTHOR]

We perform probe-tack experiments on highly viscous silicone oils. Direct observation during the experiment shows the existence of several mechanisms for releasing the stress. Beyond bubble nucleation and instantaneous growth (reported in a previous work), delayed bubble growth is observed at higher traction velocities. At even higher velocities, cracks at the interface between the plate and the liquid appear before the bubbles have grown to their full size. Bubbles and cracks are thus observed concomitantly. At much higher velocities, cracks develop fully before the bubbles can be seen. We present a theoretical model that describes these regimes, using a Maxwell fluid as a model for the actual fluid. The predictions for the force peak are in qualitative agreement with the data. We discuss to what extent a Maxwell model is adapted to this situation. In particular, we discuss the threshold value for cavitation or cracking in the case of a purely elastic material and obtain a complementary, tentative interpretation of Dahlquist's criterion for stickiness. [ABSTRACT FROM AUTHOR]

In 2012, a seroprevalence survey concerning 10 zoonoses, which were bacterial (Lyme borreliosis and Q fever), parasitic (alveolar echinococcosis [AE] and cystic echinococcosis [CE], cysticercosis, toxoplasmosis, toxocariasis, and trichinellosis), or arboviral (tick-borne encephalitis and West Nile virus infection), was conducted among 77 adult volunteers inhabiting Suordakh and Tomtor Arctic villages in the Verkhoyansk area (Yakutia). Following serological testing by enzyme-linked immunosorbent assay and/or western blot, no positive result was found for cysticercosis, CE, toxocariasis, trichinellosis, and both arboviral zoonoses. Four subjects (5.2%) had anti- Toxoplasma IgG, without the presence of specific IgM. More importantly, eight subjects (10.4%) tested positive for Lyme borreliosis, two (2.6%) for recently acquired Q fever, and one (1.3%) for AE. Lyme infection and Q fever, whose presence had not been reported so far in Arctic Yakutia, appeared therefore to be a major health threat for people dwelling, sporting, or working in the Arctic area of the Sakha Republic. [ABSTRACT FROM AUTHOR]