End-life prediction of commercial PLA used for food packaging through short term TGA experiments: Real chance or low reliability?

A long-term (about nine months) isothermal degradation experiment of two different commercial polylactide (PLA) samples used for food packaging was carried out at a relatively low temperature (423 K). Thermooxidative degradations of the same polymers were carried out in a thermogravimetric (TG) analyser, at higher temperatures (453 K ≤ T ≤ 523 K), under isothermal heating conditions. The obtained set of experimental TG data was used to determine the apparent activation energy (Ea) of degradation through two isothermal kinetic methods. The results from long-term experiment evidenced considerable mass loss for both PLA samples in the investigated period, but the experimental data were not in agreement with those from the short-term degradations at higher temperatures, thus suggesting a different degradation kinetics, and, then a low reliability of the lifetime predictions for polymers in service or degradation forecasts for the end of their life based on experiments at higher temperatures

Geopolymers—Design, Preparation, and Applications

Concrete is the most commonly used construction material worldwide, and many efforts have been carried out in recent years to improve its functional properties while also trying to increase its sustainability [...

Antibacterial Activity and Iron Release of Organic-Inorganic Hybrid Biomaterials Synthesized via the Sol-Gel Route

The aim of this work was the synthesis of hybrid materials of iron (II)-based therapeutic systems via the sol-gel method. Increasing amounts of polyethylene glycol (PEG 6, 12, 24, 50 wt%) were added to SiO2/Fe20 wt% to modulate the release kinetics of the drug from the systems. Fourier-transform infrared (FTIR) spectroscopy was used to study the interactions between different components in the hybrid materials. The release kinetics in a simulated body fluid (SBF) were investigated, and the amount of Fe2+ released was detected via ultraviolet-visible spectroscopy (UV-Vis) after reaction with ortho-phenanthroline. Furthermore, biological characterization was carried out. The bioactivity of the synthesized hybrid materials was evaluated via the formation of a layer of hydroxyapatite on the surface of samples soaked in SBF using spectroscopy. Finally, the potential antibacterial properties of seven different materials against two different bacteria—E. coli and S. aureus—were investigated

Thermo‑oxidative investigation on SiO2 and SiO2–ZrO2 composites prepared by sol–gel route

SiO2, ZrO2 and SiO2–ZrO2 composites at diferent percentages of zirconia were synthesized by the sol–gel method and spectroscopically characterized by Fourier transform infrared (FTIR) spectroscopy. Diferent series of composites were prepared and analyzed, as it is and with a post-preparation conditioning at 600 and 1000 °C, respectively. The calcination were carried out to verify the changing in composite structure and whether these treatments will afect the subsequently characterization. In fact, silica, zirconia and their composites were than subjected to oxidative degradation up to 800 °C by the means of thermogravimetric analysis (TGA). Residues, obtained at 800 °C by the thermogravimetric (TG) scans, were analyzed by FTIR to evaluate the diferences with the spectra of the composites obtained before TGA. TG curves were discussed to describe the thermal behavior of the prepared composites and to highlight the infuence of zirconia amount on the composites degradation behavior

FT-IR Study, Thermal Analysis, and Evaluation of the Antibacterial Activity of a MK-Geopolymer Mortar Using Glass Waste as Fine Aggregate

: Food containers made from glass are separately collected from urban solid waste at 76% in most parts of Europe. The cullet glass finds its way to re-melting, while the debris is often disposed of. With this contribution, we suggest an upcycling process where glass debris is simply ground without any washing operation and added to an alkali-activated paste. Metakaolin-based geopolymer mortar added with coarsely ground glass waste as fine aggregate has been prepared via alkali activation with NaOH and Na-silicate. After 7, 14 and 28 days of room temperature curing time, the 3D geopolymer network was investigated by Fourier-transform infrared spectroscopy (FTIR). Vibrational spectra revealed the geopolymerization occurrences, results which have been supported by both FT-IR deconvoluted spectra and thermogravimetric analysis (TGA). Finally, the antibacterial properties were investigated against both gram-negative (E. coli) and gram-positive (E. faecalis) bacterial strains. The results suggest the ability of the 28 days cured geopolymers to inhibit the growth of the gram-negative bacterium assayed

Antibacterial and Chemical Characterization of Silica-Quercetin-PEG Hybrid Materials Synthesized by Sol–Gel Route

This paper aims to synthesize, via the sol–gel method, a biomaterial usable in the medical field. Here, the silica-PEG-quercetin system was evaluated in relation to the different concentrations of PEG (0, 6, 12, 24, 50 wt%) and quercetin (0, 5, 10, 15 wt%), respectively. In addition, Fourier Transform-Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and Kirby–Bauer analyses were performed. FT-IR was used to evaluate the hybrid formation and the influence of both PEG and Quercetin in the hybrid synthesized materials, SEM was used to evaluate the morphological properties, while the Kirby–Bauer test was used to understand the ability of the materials to inhibit the growth of the assayed bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus)

Bioactivity of chlorogenic acid/SiO2/PEG composite synthesized via sol-gel

Sol-gel chemistry is an attractive approach in the design of new antioxidant biomaterials. Its versatility was exploited to obtain organic-inorganic hybrid materials in which a natural antioxidant compound, namely chlorogenic acid (CGA), was entrapped, in different percentage, in matrices variously constituted in silica and PEG400. The synthetized hybrids were chemically characterized by means of FTIR and UV–Vis spectroscopy and UHPLC-HRMS techniques. The hydroxyapatite nucleation on the surfaces of all samples was detected by FT-IR analysis and confirmed by XRD analysis. The scavenging capacity towards DPPH and ABTS+ radicals appeared strongly dependent on the CGA/ PEG ratio, suggesting that CGA structural features, commonly recognized to be responsible for its antioxidant capacity, may be masked or evidenced by chemical interactions in the established network. Furthermore, in vitro cytotoxicity tests by MTT highlighted a certain selectivity against tumour cells. In fact, no cytotoxic effects were observed on NIH-3T3 fibroblast cell line up to the highest exposure dose; as a matter of fact, a marked cell viability increase was observed when hybrids with low PEG amount (6%) and high CGA (15%) were directly exposed to fibroblasts. On the contrary, viability and morphology of SHSY5Y neuroblastoma cell line resulted markedly compromised. This evidence could be due to pro-oxidant effects exerted by the synthetized materials that let us to hypothesize a selective interference vs. tumour cells’ growth

Caratterizzazione e bioattività di materiali ibridi TiO2/PEI sintetizzato attraverso il metodo sol-gel

Sintetizzare nuovi materiali ibridi organo-inorganici è da sempre l’interesse di molti ricercatori in quanto possiedono particolari proprietà che li rendono utili per diverse applicazioni (sensori ottici e chimici, componenti bioattivi nelle protesi, materiali isolanti nei circuiti microelettronici). L’utilizzo del metodo sol-gel rappresenta una tecnica promettente per la produzione di tali materiali. Attraverso questa metodologia, sono stati sintetizzati materiali ibridi utilizzando TiO2 e polieterimmide (PEI) al 6 e 12% in peso. L’interazione tra la fase organica ed inorganica è stata studiata attraverso la Spettroscopia Infrarossa con Trasformata di Fourier (FTIR), mentre la microstruttura è stata osservata con l’uso del microscopio a scansione elettronica (SEM), il microscopio a forza atomica (AFM) e diffrazione ai raggi X (XRD). Al fine di valutare la bioattività, è stata determinata la capacità di formare idrossiapatite attraverso il saggio di Kokubo[1] ed osservata con il SEM e la spettroscopia a dispersione energetica (EDS)