Using a continuous-extrusion foaming process, this study examined the effect of the processing temperature on the melt viscosity, pressure drop rate, and cell-population density of poly(lactic acid) (PLA) foams. The study was intended to understand the nucleation mechanisms in order to generate microcellular structures in neat PLA in a continuous-extrusion process using CO 2 as the blowing agent. Not only did the temperature affect the melt viscosity but also the cell nucleation rate owing to its effect on the pressure drop rate. When processed at high temperature, the melt viscosity decreased and PLA nucleated fewer bubbles, irrespective of the PLA type (amorphous vs semicrystalline), because of the lower pressure drop rate in the system. Conversely, processing at a lower temperature significantly increased the cell nucleation rate for both PLA types owing to the fact that a high melt viscosity induced a high pressure drop rate. The addition of nanoclay allowed both homogeneous and heterogeneous nucleation to occur during the foaming process. The results showed that the processing temperature is a sensible parameter to produce microcellular PLA with cell densities on the order of 10 9 cells/cm 3 and cell sizes of around 10 µm.

The use of (L)Ni( o-tolyl)Cl precatalysts (L = PAd-DalPhos or CyPAd-DalPhos) enables the C( sp)-O cross-coupling of primary, secondary, or tertiary aliphatic alcohols with (hetero)aryl electrophiles, including unprecedented examples of such nickel-catalyzed transformations employing (hetero)aryl chlorides, sulfonates, and pivalates. In addition to offering a competitive alternative to palladium catalysis, this work establishes the feasibility of utilizing ancillary ligation as a complementary means of promoting challenging nickel-catalyzed C( sp)-O cross-couplings, without recourse to precious-metal photoredox catalytic methods.

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In microcellular foaming process of wood/plastic composites, the alterations in melt viscosity induced by the addition of wood-flour into the plastic matrix play an important role during the growth and stabilization of nucleated cells. This study examined the effects of wood-flour and low molecular weight rheology modifier addition levels on the melt flow index, shear viscosity, and extensional viscosity of PLA/wood-flour composites. From the results, an effective strategy is proposed to successfully and continuously produce microcellular foamed PLA/wood-flour composites with cellular structures similar to those achieved in neat PLA foams. It consists of matching the composites' melt index value (or melt viscosity) to that of neat PLA by using a rheology modifier. Lowering the melt index of the composites from the matching value resulted in unprocessable foaming conditions owing to the increased melt viscosity, whereas cell structures slightly deteriorated by increasing the melt index of the composite above its optimum value.

A material capable of rapid, reversible molecular oxygen uptake at room temperature is desirable for gas separation and sensing, for technologies that require oxygen storage and oxygen splitting such as fuel cells (solid-oxide fuel cells in particular) and for catalytic applications that require reduced oxygen species (such as removal of organic pollutants in water and oil-spill remediation). To date, however, the lowest reported temperature for a reversible oxygen uptake material is in the range of 200-300 °C, achieved in the transition metal oxides SrCoOx (ref. 1) and LuFe₂O(4+x) (ref. 2) via thermal cycling. Here, we report rapid and reversible oxygen scavenging by Ti(2-x) nanotubes at room temperature. The uptake and release of oxygen is accomplished by an electrochemical rather than a standard thermal approach. We measure an oxygen uptake rate as high as 14 mmol O₂ g(-1) min(-1), ∼2,400 times greater than commercial, irreversible oxygen scavengers. Such a fast oxygen uptake at a remarkably low temperature suggests a non-typical mechanistic pathway for the re-oxidation of Ti(2-x). Modelling the diffusion of oxygen, we show that a likely pathway involves 'exceptionally mobile' interstitial oxygen produced by the oxygen adsorption and decomposition dynamics, recently observed on the surface of anatase.