Nanocomposites and a composite based on poly(butylene adipate-co-terephthalate) (PBAT) were synthesized using commercial copper nanoparticles (Cu-NPs), copper/cuprous oxide nanoparticles (Cu|Cu 2 O-NPs), and copper sulfate (CuSO 4 ), respectively. The Cu|Cu 2 O-NPs were synthesized using chemical reduction and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The synthesis of Cu|Cu 2 O-NPs yielded a mixture of Cu and Cu 2 O, with metal Cu having a spherical morphology of approximately 40 nm in diameter and Cu 2 O with a diameter of 150 nm. To prepare the nanocomposites (NCs) and the composite material (MC), the NPs and the CuSO 4 salt were incorporated into the PBAT matrix in concentrations of 1, 3, and 5% p/p via an ex situ method. Fourier transform infrared spectroscopy (FTIR), a tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and agar diffusion assays were used for structural, thermomechanical, and antimicrobial characterization. Results showed that the reinforcements did not modify the chemical structure of the PBAT and only slightly increased the percentage of crystallization. The mechanical and thermal properties of the PBAT did not change much with the addition of fillers, except for a slight increase in tensile strength and thermal stability, respectively. The agar diffusion antimicrobial assays showed that the NCs and MCs had good inhibitory responses against the nonresistant strains Enterococcus faecalis , Streptococcus mutans , and Staphylococcus aureus . The MCs based on CuSO 4 had the highest biocidal effect, even against the resistant bacteria Acinetobacter baumannii . Electronic supplementary material The online version of this article (10.1186/s11671-019-2987-x) contains supplementary material, which is available to authorized users.

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Poly(butylene adipate‐co‐terephthalate) (PBAT) was mixed with copper nanoparticles (Cu‐NPs) in concentrations of 1%, 3%, and 5% with particle size between 100 nm and 200 nm by the melting method. A morphological, thermal, and structural characterization of the nanocomposites (NCs‐PBAT/Cu) was performed to analyze the effect of the Cu‐NPs on the polymer chains, as well as to explain the influence on their crystallinity, and its influence on the thermomechanical and antibacterial properties. The percentage of crystallinity (Xc) increased 6.7% to 9.5% with the amount of Cu‐NPs in the matrix. E‐modulus was slightly improved from 84.04 to 87.7 MPa, in the same way the degradation temperature (Td) of the PBTA was improved from 420.7°C to 427.2°C for 5% loading of Cu‐NPs. In contrast, ΔHm decreased from 12.50 to 6.96 J/g, indicating that there was no significant modification of the PBAT chain, mainly by heterogeneous nucleation in the presence of Cu‐NPs, which act as a heat barrier. No blue or red shifts we observed in the nanocomposites Fourier transform infrared (FTIR) spectra, indicating there is no effective interaction between PBAT and Cu‐NPs. The nanocomposites showed excellent antibacterial properties inhibiting 100% of the strains Enterococcus faecalis, Streptococcus mutans, and Staphylococcus aureus, at 2 hours of treatment. For more resistant strains such as Acinetobacter baumannii, the NCs‐PBAT/Cu did not show antibacterial activity at any time of treatment. POLYM. COMPOS., 40:1870–1882, 2019. © 2018 Society of Plastics Engineers

The Chilean workforce has over 200,000 people that are intermittently exposed to altitudes over 4,000 m. In 2012, the Ministry of Health provided a technical guide for high-altitude workers that included a series of actions to mitigate the effects of hypoxia. Previous studies have shown the positive effect of oxygen enrichment at high altitudes. The Atacama Large Millimeter/submillimeter Array (ALMA) radiotelescope operates at 5,050 m [Array Operations Site (AOS)] and is the only place in the world where pressure swing adsorption (PSA) and liquid oxygen technologies have been installed at a large scale. These technologies reduce the equivalent altitude by increasing oxygen availability. This study aims to perform a retrospective comparison between the use of both technologies during operation in ALMA at 5,050 m. In each condition, variables such as oxygen (O2), temperature, and humidity were continuously recorded in each AOS rooms, and cardiorespiratory variables were registered. In addition, we compared portable O2 by using continuous or demand flow during outdoor activities at very high altitudes. The outcomes showed no differences between production procedures (PSA or liquid oxygen) in regulating oxygen availability at AOS facilities. As a result, big-scale installations have difficulties reaching the appropriate O2 concentration due to leaks in high mobility areas. In addition, the PSA plant requires adequacy and maintenance to operate at a very high altitude. A continuous flow of 2–3 l/min of portable O2 is recommended at 5,050 m.