Effectual dispersion of carbon nanofibers in polyetherimide composites and their mechanical and tribological properties

The use of proliferation of nanotechnology in commercial applications is driving requirements for minimal chemical processing and simple processes in industry. Carbon nanofiber (CNF) products possess very high purity levels without the need of purification processing before use and are in growing demand for this quality. Polyetherimide (PEI) has excellent mechanical and thermal performance, but its high viscosity makes its nanocomposites processing very challenging. In this study, a facile melt‐mixing method was used to fabricate PEI nanocomposites with as received and physically treated CNFs. The dispersion of CNFs was characterized by scanning electron microscopy, transmitted optical microscopy, and electrometer with large‐area electrodes. The results showed that the facile and powerful melt‐mixing method is effective in homogeneously dispersing CNFs in the PEI matrix. The flexural and tribological characteristics were investigated and the formation of spatial networks of CNFs and weak interfacial bonding were considered as competitive factors to enhanced flexural properties. The composites with 1.0 wt% CNFs showed flexural strength and toughness increased by more than 50 and 550%, respectively, but showed very high wear rate comparable with that of pure PEI. The length of the CNFs also exerted great influences on both mechanical and tribological behaviors. POLYM. ENG. SCI., 50:1914–1922, 2010. © 2010 Society of Plastics Engineers     

Hydrogen production through anaerobic co-digestion of food waste and crude glycerol at mesophilic conditions

Hydrogen production from mesophilic anaerobic co-digestion of food waste (FW) and crude glycerol (GLC) was investigated in this study. Batch experiments were carried out at 35 °C for 36 h to assess the effect of supplementation of different glycerol concentrations (1%, 3% and 5% (v/v)) on dark fermentation of FW. The maximum hydrogen yield (180 mLH₂/gVS) was obtained at 5% GLC while the maximum specific production rate (around 13 mLH₂/(gVS.h)) was similar for all experiments with glycerol addition. Besides contributing to increase H₂ productivity, the presence of glycerol reduced the microorganisms acclimation time (Lag phase) in comparison to the control tests conducted without this co-substrate. In addition, the increment of glycerol concentration also enhanced volatile fatty acids generation and favoured the production of 1,3-propanediol (1,3-PDO). In the experimental conditions studied (i.e., 1–5% (v/v) of GLC), the results revealed that co-digestion of FW and GLC is promising and can be potentially used to maximize energy production while contributing to the management and treatment of these wastes.     

Flavour compounds of Lavandula angustifolia L. to use in food manufacturing: Comparison of three different extraction methods

Sixty compounds of Lavandula angustifolia L. cultivated in Friuli Venezia Giulia (North-East Italy) were identified and quantified by GC-MS and GC-FID from essential oils obtained by means of hydrodistillation, and from extracts obtained by supercritical CO₂ extraction (SFE) and ultrasound-assisted extraction (US). Using absolute calibration, a true quantification of 1-8 cineol, camphor, linalool, linalyl acetate and β-caryophyllene was carried out. The best extracts, in terms of amount of isolated compounds, flavour quality and stability were those obtained with SFE. Sonication performed at low amplitude for 5 min offered respect to high amplitude a promising alternative to hydrodistillation as a source of lavender flavouring ready to use for alcoholic beverages or/and confectionery products.     

Evaluation of Alternative Preservation Treatments (Water Heat Treatment,Ultrasounds, Thermosonication and UV-C Radiation) to Improve Safety and Quality of Whole Tomato

Previously optimised postharvest treatments were compared to conventional chlorinated water treatment in terms of their effects on the overall quality of tomato (‘Zinac’) during storage at 10 °C. The treatments in question were water heat treatment (WHT?=?40 °C, 30 min), ultrasounds (US?=?45 kHz, 80 %, 30 min), thermosonication (TS?=?40 °C, 30 min, 45 kHz, 80 %) and ultraviolet irradiation (UV-C: 0.97 kJ m^?2). The quality factors evaluated were colour, texture, sensorial analysis, mass loss, antioxidant capacity, total phenolic content, peroxidase and pectin methylesterase enzymatic activities, and microbial load reduction. The results demonstrate that all treatments tested preserve tomato quality to some extent during storage at 10 °C. WHT, TS and UV-C proved to be more efficient on minimising colour and texture changes with the additional advantage of microbial load reduction, leading to a shelf life extension when compared to control trials. However, at the end of storage, with exception of WHT samples, the antioxidant activity and phenolic content of treated samples was lower than for control samples. Moreover, sensorial results were well correlated with instrumental colour experimental data. This study presents alternative postharvest technologies that improve tomato (Zinac) quality during shelf life period and minimise the negative impact of conventional chlorinated water on human safety, health and environment.     

Surface properties of phenolic compounds and their influence on the dispersion degree and oxidative stability of olive oil O/W emulsions

The surface and interfacial properties of gallic acid, catechin and quercetin, and their effect on the dispersion degree and the oxidative stability of olive oil oil-in-water (O/W) emulsions prepared using β-lactoglobulin and Tween 20 were studied.Gallic acid showed no effect on the surface properties while catechin was proven to be able to accumulate at the air/water interface, decreasing the surface tension values with increasing its concentration. All the phenolic antioxidants caused a decrease in the interfacial tension at the oil/water interface, even though only catechin and quercetin showed a concentration dependent behaviour.In emulsions, gallic acid did not affect the droplet size of the systems, catechin caused the formation of oil droplets bigger than those of the control, whilst quercetin improved the dispersion state of the emulsions with the increasing of its concentration. Gallic acid, despite its partitioning in the water phase due to its polarity, delayed the formation of both the hydroperoxides and TBARs and limited their accumulation. Catechin did not affect the formation of oxidation products whilst quercetin, among the tested antioxidants, caused the lowest formation of both hydroperoxides and TBARs through 33 days of storage.     

Hydrogen production from methane steam reforming: parametric and gradient based optimization of a Pd-based membrane reactor

In this work three mathematical models for methane steam reforming in membrane reactors were developed. The first one is a steady state, non isothermal, non isobaric and one dimensional model derived from material and energy balances and validated using experimental data from the literature. It is referred as full model. The influence of two different intrinsic kinetics available, as well as, the influence of five important parameters on methane conversion (X_CH4_{\mathrm{CH}_{4}}) and hydrogen recovery (Y_H2_{\mathrm{H}_{2}}) were parametrically evaluated through simulations. The second model, referred as meta-model, was obtained though the response surface technique. This meta-model was included into a constrained optimization problem solved using NPSOL. The third model, referred as a simplified model, takes into account only mass balances from the full model. Using this model, a gradient based method (DIRCOL) was used to perform the optimization of the sum of methane conversion and hydrogen recovery. High methane conversions and hydrogen recoveries were reached through these methodologies.