Application of electron paramagnetic resonance (EPR) spectroscopy for control of irradiated food

Four groups of foodstuffs were irradiated in a ⁶⁰Co source with doses from 0.3 to 10kGy and subsequently measured by EPR spectrometry at room temperature in air: (1) poultry bones and fins, scales and bones of carp. (2) seeds of selected fruits, (3) dehydrated mushrooms, and (4) a selected set of spices and herbs. Qualitative and, in some cases, quantitative data related to the absorbed dose of radiation were collected. In the irradiated bones from poultry and carp an asymmetric singlet (g_I = 2.0030, g_II =1.9973; ΔH_pp = 0.85 mT) was detected which was stable at room temperature and was similar to that previously found in irradiated mammalian bones. Another stable EPR signal (g₀ = 2.0024, ΔH_pp = 0.56 mT) was found in the fins and scales of carp which was about five times more intense in fins than in scales. In pips of pears irradiated with a dose of 3 kGy. a signal which was about twice as intense as the endogenous signal was recorded. A multicomponent EPR signal derived from the stones of dates differed from the endogenous signal even when a low dose (0-5 kGy) was applied. A multicomponent EPR signal is also observed in dried mushrooms irradiated with a dose of 3 kGy. In white mustard, paprika and chilli no native EPR signal exists and a radiation-induced stable EPR signal can still be observed after a period of 3 months. The radiation-induced EPR signal in black pepper was highly sensitive to moisture and disappeared, yet the native signal survived. The pilot experiments performed with irradiated stones of cherries, plums, lemons, apple pips, raspberries, cranberries, red currants, blackcurrants, gooseberries and tomatoes showed the induction of short-lived EPR signals of no practical use for the control of food irradiation.     

A Basic Theoretical Model for Friction Process at Microasperity Level

This article presents a theoretical model for dry, low-velocity, and wear-less friction based on a single asperity interaction with arbitrary assumed adhesion forces and elastic deformations of the microasperities. Simulations of friction behavior according to the single asperity interaction, as well as the interaction of multiplied single models, are presented. The multiplied model assumes a regular distribution of the single asperities, arbitrarily chosen geometrical properties (based on harmonic function), and elastomechanical properties of the cooperating materials. In the proposed model, the adhesion as a function of asperity deformation is introduced. This enables the simulation of an expedient local coefficient of friction. The model assumes no breaking of the contact between single asperities; however, the proposed model enables detection of such a situation. The results obtained by simulation of the model show both qualitative and quantitative agreement with the known types of friction force dynamic behavior, in particular, nonlinearity of the friction coefficient. At this level of investigation, the model assumes the most important relations connected with its properties, which need further refinement and elaboration, especially according to assumed asperity properties.     

The hildebrand solubility parameters of ionic liquids-part 2

The Hildebrand solubility parameters have been calculated for eight ionic liquids. Retention data from the inverse gas chromatography measurements of the activity coefficients at infinite dilution were used for the calculation. From the solubility parameters, the enthalpies of vaporization of ionic liquids were estimated. Results are compared with solubility parameters estimated by different methods.     

Silane–parylene coating for improving corrosion resistance of stainless steel 316L implant material

The corrosion resistance of a two-layer polymer (silane + parylene) coating, on implant stainless steel was investigated by microscopic observations and electrochemical measurements. Long term exposure tests in Hanks solution revealed that the coating of 2 μm can be successfully used for corrosion protection. However, the addition of H₂O₂, simulating the inflammatory response of human body environment causes a dramatic destruction of the protective coating. Analysis of the experimental data in terms of circuit models enables proposing a deterioration mechanism. OH radicals formed at the metal surface attack the polymer, thus the deterioration starts from the metal/polymer interface and progress towards the outward surface.     

New Non Phyto‐ and Eco‐Toxic Alumina‐Stabilized Silver and Praseodymium Nanoparticles

In the present study, we examined how the active aluminum nano‐oxide in the gamma form used as a neutral carrier for the nanoparticles of various metals (as Ag, Pr) affected their toxic behavior. Our experiments have shown that exposure to metal nanoparticles can be reduced by binding the nanoparticles to alumina nanoparticles and the aluminum nano‐oxide is suitable to function as the nano‐stabilizer for the Ag and Pr nanoparticles. We have managed to manufacture new alumina‐stabilized silver and praseodymium nanoparticles using dry sol‐gel method that are not phyto‐ and eco‐toxic.     

Dynamic mechanical thermal analysis of biocomposites based on PLA and PHBV—A comparative study to PP counterparts

The primary objective of this study was the investigation of thermo‐mechanical behavior of cellulosic fiber reinforced polylactid (PLA) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) biopolymers. Both PLA and PHBV were processed with 30 wt % of cellulosic fibers; moreover, to improve the processability and mechanical performance, PHBV was previously blended with 30% by weight poly(butylene adipate‐co‐butylene terephthalate) (PBAT). Secondary target was the comparison of the obtained results to natural fiber reinforced polypropylene (PP) composites reinforced with exact the same fibers and processed by using identical techniques. For validation the thermo‐mechanical properties, a dynamic mechanical thermal analysis (DMTA) was applied. Storage modulus (E′), loss modulus (E″), and loss factor (tan δ) were determined. The DMTA results indicate decreased polymer chain motion with resulting improvement of stiffness expressed by the storage modulus. Finally, the effectiveness of fiber on the moduli was investigated. The C coefficient differs in dependence on fiber type, use of coupling agent, and the reference temperature in glassy state. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3175–3183, 2013     

Modification of epoxy–anhydride thermosets with a hyperbranched poly(ester amide). II. Thermal,dynamic mechanical,and dielectric properties and thermal reworkability

An epoxy–anhydride formulation used for the coating electrical devices was modified with a commercially available hyperbranched poly(ester amide), Hybrane S2200, to improve the thermal degradability of the resulting thermoset and, thus, facilitate the recovery of substrate materials after the service life of the component. The thermomechanical, mechanical, and dielectric properties and thermal degradability were studied and interpreted in terms of the composition and network structure of the cured thermosets. Although the crosslinking density was significantly reduced with the incorporation of S2200, the glass transition temperature of the fully cured material (T_g∞) of the modified thermoset was hardly affected because of the enhancement of H‐bonding interactions in the presence of S2200. Despite the different network structures, the combined dielectric and dynamic mechanical analysis revealed that the relaxation dynamics of both networks were very similar. In terms of application, improvements in the dielectric and mechanical properties were observed. The incorporation of S2200 accelerated the thermal decomposition of the material and, thus, facilitated the recovery of the valuable parts from the substrate at the end of the service life of the apparatus. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Stresses Generated During Convective and Microwave Drying

Abstract

An outline of the mechanistic model of convective and microwave drying of saturated capillary-porous materials is presented. The model was derived in the framework of irreversible thermodynamics. Particular attention is devoted to construction of the term describing the power of microwave radiation absorbed per unit volume, which is converted into internal heat source. The qualitative difference in distribution of temperature, moisture content, and the drying-induced stresses in materials under convective and microwave drying is illustrated in the examples of cylindrical kaolin samples. The diagrams of acoustic emission are taken off on-line from these samples in order to illustrate the development of material destruction caused by the stresses induced during both convective and microwave drying.     

Modeling of Ozone Reaction with Benzaldehyde Incorporating Ozone Decomposition in Aqueous Solutions

Ozonation of benzaldehyde in its aqueous solutions based on mechanistic approach and incorporating ozone decomposition model is presented in this work. As the basis the modified and extended HSB model of ozone decomposition with phosphates and carbonates reactions included has been applied. It was then tuned with the literature data and the results of our own measurements on ozone decay in aqueous solutions. The model was extended to model benzaldehyde oxidation reactions in the aqueous solutions. Model predictions compare favorably against experimental data obtained in the range of pH 2.3 to 8 with or without radical scavenger (t-butanol).     

Interlaminar fracture toughness behavior of electron‐beam cured carbon‐fiber reinforced epoxy–resin composites

The work describes the preparation and physical‐mechanical characterization of unidirectional CFRP panels manufactured by an electron beam curing technique. Delamination fracture toughness in Mode I and II is investigated in order to evaluate the influence of fiber–matrix adhesion strength, matrix toughness and matrix crosslinking density as determined by the radiation curing process. A matrix system comprising a DGEBA epoxy monomer and an initiator of cationic polymerization have been used, with one batch of resin mixed with a PES monomer in order to enhance matrix toughness. Curing was achieved with a pulsed 10 MeV Electron Beam accelerator. Thermally cured composite systems have also been manufactured and tested for comparison. Results from double cantilever beam and end notched flexure delamination tests have been analyzed and correlated with results from short beam shear, dynamic mechanical thermal analysis tests and SEM micrographs of delaminated surfaces. POLYM. COMPOS., 35:1529–1542, 2014. © 2013 Society of Plastics Engineers