Silvia Goyanes

Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent.

Biodegradable and non-retrogradable starch-glycerol based films were obtained using citric acid (CA) as crosslinking agent at 75°C. This material allowed decreasing water vapor permeability (WVP) more than 35%, remained amorphous for at least 45 days as a result of the network formed by the CA that avoided starch retrogradation and maintained the degradability in compost, occurring only six days after the films without citric acid. A simulation of the gelatinization process of starch-glycerol with and without CA, using a differential thermal analysis device, showed that the system with CA completed the gelatinization 5°C before than the other and, CA first reacted with glycerol and then starch-glycerol-CA reaction occurred. The temperature at which the gelatinization process was carried out was critical to obtain the best results. An increase of gelatinization process temperature at 85°C in system with CA, led to a worsening on WVP and its integrity after a swelling process with dimethylsulphoxide (DMSO), compared to the films processed at 75°C.

Application of multi-walled carbon nanotubes as substrate for the on-line preconcentration, speciation and determination of vanadium by ETAAS

This paper presents the development of a pre-concentration and speciation method for inorganic vanadium species by flow injection solid phase extraction-electrothermal atomic absorption spectrometry (FI-SPE-ETAAS). This was carried out by employing a conical mini-column filled with multi-walled carbon nanotubes mounted in the arm of the autosampler of the ETAAS. This system was applied to the on-line pre-concentration and speciation of vanadium in natural waters in conjunction with ETAAS determination. The time required for the pre-concentration of 1.0 ml of sample (1.0 ml min−1), elution/injection (0.2 ml min−1), reading/data acquiring and conditioning was about 2.9 min, resulting in a sample throughput of 20 samples per hour. A 20-fold total enrichment factor for a sample volume of 1.0 ml was obtained with respect to the vanadium determination by ETAAS without pre-concentration. The relative standard deviation for six replicates containing 200 ng l−1 was 3.3%. A limit of detection (3s) of 19 ng l−1 was achieved and the limit of quantification was estimated (10s), obtaining a characteristic concentration of 63 ng l−1. The calibration curve was linear from the quantification limit up to 1500 ng l−1, with a correlation coefficient of 0.9996. This method permitted us to determine the total inorganic vanadium in natural waters. For speciation purposes, V(IV) was masked with 1,2 cyclohexanediaminetetraacetic acid (CDTA) in order to determine the V(V) concentration selectively.

Improving the physical properties of starch using a new kind of water dispersible nano-hybrid reinforcement

Plasticized cassava starch matrix composites reinforced by a multi-wall carbon nanotube (MWCNT)-hercynite (FeAl2O4) nanomaterial were developed. The hybrid nanomaterial consists of FeAl2O4 nanoparticles anchored strongly to the surface of the MWCNT. This nano-hybrid filler shows an irregular geometry, which provides a strong mechanical interlocking with the matrix, and excellent stability in water, ensuring a good dispersion in the starch matrix. The composite containing 0.04wt.% of the nano-hybrid filler displays increments of 370% in the Youngs modulus, 138% in tensile strength and 350% in tensile toughness and a 70% decrease in water vapor permeability relative to the matrix material. All of these significant improvements are explained in terms of the nano-hybrid filler homogenous dispersion and its high affinity with both plasticizers, glycerol and water, which induces crystallization without deterioration of the tensile toughness.

Biodegradable Starch Nanocomposites

Biodegradable thermoplastic materials offer great potential to be used in food packaging or biomedical industry. In this chapter we will present a review of the research done on starch and starch nanocomposites. In the case of nanocomposites based on starch, special attention will be given to the influence of starch nanoparticles, cellulose whiskers, zinc oxide nanorods, antioxidants, and antimicrobial inclusion on the physicochemical properties of the materials. The discussion will be focused on structural, mechanical, and barrel properties as well as on degradation, antibacterial and antioxidant activities. Finally, we will discuss our perspectives on how future research should be oriented to contribute in the substitution of synthetic materials with new econanocomposites.

A simple green route to obtain poly(vinyl alcohol) electrospun mats with improved water stability for use as potential carriers of drugs.

Poly(vinyl alcohol) (PVA) is a hydrophilic, biocompatible and nontoxic polymer. However, because of its low water-resistance, some applications for PVA-based materials are limited (e.g., drug delivery systems and wound dressings). In the current work, PVA mats containing tetracycline hydrochloride (TC) were successfully developed by electrospinning. In order to improve the water stability of the systems, the cross-linking of the PVA matrix was induced by citric acid (CA) addition together with heating treatments (150°C or 190°C for 3min). TC presence led to a strong increase in the electrical conductivity of the blends and as a result, fibers with about 44% lower diameter (270nm) than that of the corresponding unloaded mats (485nm) were obtained. Laser scanning confocal microscopy images indicated that TC was well distributed along the PVA nanofibers. The mats were evaluated by FTIR, which revealed chemical interactions between PVA hydroxyl groups and CA carboxylic ones. The treatment at 150°C for 3min proved to be the more suitable for the preparation of TC-containing mats with improved water resistance, maintaining the TC antimicrobial activity against both Escherichia coli and Staphylococcus aureus almost unaltered. These mats showed a burst release of TC, giving around 95% of the drug within the first hour of immersion in water.

High-Energy Dissipation Performance in Epoxy Coatings by the Synergistic Effect of Carbon Nanotube/Block Copolymer Conjugates

Hierarchical assembly of hard/soft nanoparticles holds great potential as reinforcements for polymer nanocomposites with tailored properties. Here, we present a facile strategy to integrate polystyrene-grafted carbon nanotubes (PSgCNT) (0.05-0.3 wt %) and poly(styrene-b-[isoprene-ran-epoxyisoprene]-b-styrene) block copolymer (10 wt %) into epoxy coatings using an ultrasound-assisted noncovalent functionalization process. The method leads to cured nanocomposites with core-shell block copolymer (BCP) nanodomains which are associated with carbon nanotubes (CNT) giving rise to CNT-BCP hybrid structures. Nanocomposite energy dissipation and reduced Youngs Modulus (E*) is determined from force-distance curves by atomic force microscopy operating in the PeakForce QNM imaging mode and compared to thermosets modified with BCP and purified carbon nanotubes (pCNT). Remarkably, nanocomposites bearing PSgCNT-BCP conjugates display an increase in energy dissipation of up to 7.1-fold with respect to neat epoxy and 53% more than materials prepared with pCNT and BCP at the same CNT load (0.3 wt %), while reduced Youngs Modulus shows no significant change with CNT type and increases up to 25% compared to neat epoxy E* at a CNT load of 0.3 wt %. The energy dissipation performance of nanocomposites is also reflected by the lower wear coefficients of materials with PSgCNT and BCP compared to those with pCNT and BCP, as determined by abrasion tests. Furthermore, scanning electron microscopy (SEM) images taken on wear surfaces show that materials incorporating PSgCNT and BCP exhibit much more surface deformation under shear forces in agreement with their higher ability to dissipate more energy before particle release. We propose that the synergistic effect observed in energy dissipation arises from hierarchical assembly of PSgCNT and BCP within the epoxy matrix and provides clues that the CNT-BCP interface has a significant role in the mechanisms of energy dissipation of epoxy coating modified by CNT-BCP conjugates. These findings provide a means to design epoxy-based coatings with high-energy dissipation performance.

Effect of O2+, H2++ O2+, and N2++ O2+ ion-beam irradiation on the field emission properties of carbon nanotubes

The effect of O2+, H2++ O2+, and N2++ O2+ ion-beam irradiation of carbon nanotubes (CNTs) films on the chemical and electronic properties of the material is reported. The CNTs were grown by the chemical vapor deposition technique (CVD) on silicon TiN coated substrates previously decorated with Ni particles. The Ni decoration and TiN coating were successively deposited by ion-beam assisted deposition (IBAD) and afterwards the nanotubes were grown. The whole deposition procedure was performed in situ as well as the study of the effect of ion-beam irradiation on the CNTs by x-ray photoelectron spectroscopy (XPS). Raman scattering, field-effect emission gun scanning electron microscopy (FEG-SEM), and field emission (FE) measurements were performed ex situ. The experimental data show that: (a) the presence of either H2+ or N2+ ions in the irradiation beam determines the oxygen concentration remaining in the samples as well as the studied structural characteristics; (b) due to the experimental conditions used i...

Improving bone cement toughness and contrast agent confinement by using acrylic branched polymers

A new biomedical material to be used as part of acrylic bone cement formulations is described. This new material is tough, its Youngs Modulus is similar to the one of poly (methylmethacrylate) and the contrast agent, usually employed in acrylic bone cements, is homogeneously distributed among the polymeric matrix. Additionally, its wear coefficient is 66% lower than the one measured in poly(methyl methacrylate). The developed material is a branched polymer with polyisoprene backbone and poly(methyl methacrylate) side chains, which are capable of retaining barium sulphate nanoparticles thus avoiding their aggregation. The grafting reaction was carried out in presence of the nanoparticles, using methyl methacrylate as solvent. From the (1)H-NMR spectra it was possible to determine the average number of MMA units per unit of isoprene (3.75:1). The ability to retain nanoparticles (about 8wt.%), attributed to their interaction with the polymer branches, was determined by thermogravimetric analysis and confirmed by FTIR and microscopy techniques. By SEM microscopy it was also possible to determine the homogeneous spatial distribution of the barium sulphate nanoparticles along the polymer matrix.

Data of thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid as crosslinking agent.

Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: “Biodegradable and non-retrogradable eco-films based on starch–glycerol with citric acid as crosslinking agent” González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature.

Synthesis and Characterization of ZnO Nanorod Films on PET for Photocatalytic Disinfection of Water

Abstract ZnO nanorods (ZnO NRs) were grown on ZnO seeded polyethylene tert-phtalate (PET) substrates obtained from recycled soda bottles at low temperatures (90 °C) from Zn2+ precursors in alkaline aqueous solution. The ZnO seeds were deposited on the PET substrates by spray gel (SG) or dip coating (DC) from a ZnO methanol sol. In the case of SG, the PET substrate was heated at 90 °C during the spray process. By the other hand the ZnO seed layers obtained by dip coating were heated at 90 °C or 130 °C for 10 minutes among coatings. Before seeding two procedures were made on PET surface for improving seed adhesion: 1) PET surface was mechanically roughened with sand paper 1200. 2) PET surface was chemically treated with a solution of NaOH in ethanol. The relationship between the microstructure of the ZnO NRs films as function of the PET surface treatment and the photocatalytic antibacterial activity for E. Coli disinfection, was determined through a detailed characterization of the material. The highest photocatalytic antibacterial activity was performed by ZnO NRs films grown on seeds deposited by dip coating with 10 layers, 5 minutes of chemical treatment of PET surface and a thermal treatment at 130° C among coatings. With these films the population of viable E. Coli dropped more than seven orders, from 3×108 to 101 CFU.