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We investigated the continuous extrusion foaming of poly­(vinyl alcohol) (PVOH)/microfibrillated cellulose (MFC) composites using supercritical carbon dioxide (scCO2) as the blowing agent. First, the as-received PVOH pellets were compounded with water to decrease their melting point. Then, they were compounded with an MFC solution to prepare the sample. Both scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) showed that the MFC dispersed well in the PVOH/MFC composites. Differential scanning calorimetry (DSC) results showed that adding MFC affected the thermal behavior. This, in turn, affected cell nucleation and cell growth phenomena during foam extrusion. Water also acted as a co-blowing agent, together with scCO2, in creating biodegradable polymer foams with a uniform cell structure and a high cell density. The effects of the MFC content, scCO2 content, and die temperature variations on the cell density and cellular morphology of the PVOH/MFC composite foams were examined systematically.

OBJECTIVE: Once penetrated into the stratum corneum, anionic surfactants bind to and denature stratum corneum proteins as well as intercalate into and extract intercellular lipids. With repeated exposures, this leads to skin dryness and irritation, compromising barrier function and skin health. The mechanisms of anionic surfactant penetration into the skin, however, are still widely debated. The objective of this study was to evaluate current theories of surfactant penetration into human skin. METHODS: A test set comprising 15 anionic surfactant systems and one non-ionic surfactant, all having either dodecyl or lauryl alkyl chains, was tested for surfactant penetration into split-thickness human cadaver skin in vitro using radiolabelled sodium dodecyl sulphate ( 14 C-SDS). Select physical properties of these formulations thought to be associated with skin penetration including critical micelle concentration, micelle diameter, filtrate concentration and zeta potential were also measured. RESULTS: 14 C-SDS penetration into human cadaver skin from surfactant systems in vitro was found to correlate well with CMC (R 2 = 0.34, P < 0.05), filtrate concentration (R 2 = 0.36, P < 0.05) and zeta potential (R 2 = 0.76, P < 0.001), but poorly with micelle diameter (R 2 = 0.12). Furthermore, the latter measure correlated inversely with penetration compared to what would be expected based on the micelle penetration theory. CONCLUSION: Neither monomer nor micelle penetration theories are sufficient to explain anionic surfactant penetration into human skin. Submicellar (or premicellar) aggregate penetration theory is difficult to defend at relevant surfactant concentrations. We propose a new hypothesis for this mechanism in which short-term penetration is based on monomer concentration and longer term penetration is based on surfactant-induced damage to the skin barrier.

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The crystal structure of the title compound has been determined (space group Pbca, a = 10.293(4), b = 22.665(8), c = 12.218(4) Â, Ζ = 8) and refined to R = 0.065. Bond lengths in the acetal group differ appreciably from those in related equatorial 2-aryloxy acetals.