Physicochemical Properties of Calcium Caseinate Films Cross-Linked by Gamma-Irradiation

Gamma-irradiation was used to produce freestanding, sterilized, cross-linked caseinate films and gels. Mechanical properties of gels and films and water vapor permeability of dried films were determined. Irradiated films were significantly ( p ≤0.05) more resistant to puncture and moisture. Also, gels were formed when protein solutions received radiation doses ≥16 kGy. The addition of CaCl 2 in the solution containing proteins, glycerol, and carboxymethylcellulose (base formulation) increased significantly the puncture strength for the films atirradiation doses ≥16 kGy. Sorbitol had the greatest plasticizing effect andsignificantly ( p ≤0.05) increased distance to puncture, while mannitoldecreased distance to puncture. Size-exclusion chromatography performed on the irradiated solutions of the base formulation showed that gamma-irradiation increased the molecular weight of calcium caseinate by 100 times; the molecular weight was ≥2×10 3 kDa. Films produced with base formulation were alsoimmersed in flasks containing 100mL of boiling water during 30 min forinsolubility measurements. Results showed that the proportion of the insolublefraction increased with the irradiationdose. Seventy percent of the irradiated films (32 kGy) remained insoluble after immersion in water at 100°C, 30 min and 20°C, 24 h. Water vapor permeability (WVP) of the base formulation films was reduced from 3.99±0.23 to 2.57±0.63 g.mm/m 2 .d.mmHg after irradiationtreatment. Microbial resistance of cross-linked films (base formulation)showed that 36% of N from calcium caseinate films was converted to soluble N after 60 d in presence of Pseudomonas aeruginosa .     

Water vapor absorption and permeability of films based on chitosan and sodium caseinate

The objective of this work was to characterize the moisture sorption and water vapor permeation behavior of edible films made from sodium caseinate and chitosan for future applications as protective layers on foods. Glycerol was used as a plasticizer, and the films were obtained by a casting/solvent‐evaporation method. The moisture sorption kinetics and water vapor permeability (WVP) were investigated. The effect of the addition of glycerol on the WVP characteristics of the films was determined at 25°C with a relative humidity (RH) gradient of 0–64.5% (internal to external). Experimental data were fitted with an exponential function with two fitting parameters. WVP increased with increasing glycerol content in both films, chitosan samples being much more permeable than caseinate ones at any glycerol content. WVPs of sodium caseinate, chitosan, and chitosan/caseinate films with 28 wt % glycerol were also determined for two RH gradients, 0 to 64.5% and 100 to 64.5%, higher WVPs being measured at higher RHs. The moisture sorption kinetics of caseinate films prepared with various glycerol contents were determined by the placement of the films in environments conditioned at 20°C and 75% RH. Peleg's equation and Fick's second law were used to predict the moisture sorption behavior over the entire time period. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of the SiO2/Al2O3 ratio on the synthesis and physicochemical characteristics of levyne-type zeolite

Levyne-type zeolites were synthesized from gels of initial compositions 4.5Na₂O-6MeQI-xAl₂O₃ 30SiO₂-500H₂O, with MeQ = methylquinuclidinium and 0.6 ≤ x ≥ 3 at 150 ≤ t ≥ 190 °C. The ²⁹Si NMR spectra show the presence of two crystallographically different sites in the structure. The ²⁷Al NMR spectra also suggest the presence of two different tetrahedral Al atoms incorporated in the structure. A rather high amount of defect groups SiOM and Si(OM)₂ with M = MeQ, Na and/or H are present in the precursor samples. The Si(OM)₂ groups are eliminated during calcination, and a certain amount of SiOM still persists after calcination. The combined ¹³C NMR and thermal analysis data allowed one to interpret the nature of the two different types of MeQ⁺ ions occluded in the levyne channels.     

Mechanical and barrier properties of carbon nanotube reinforced PCL‐based composite films: Effect of gamma radiation

Carbon nanotube (CNT) reinforced (0.05–0.5% by wt) polycaprolactone (PCL)‐based composites were prepared by compression molding. Addition of 0.2% CNT caused a 131% improvement of tensile strength (TS) of PCL films. The tensile modulus (TM) and elongation at break (Eb) of PCL were also significantly improved with the addition of CNT. The water vapor permeability of PCL was 1.51 g·mm/m²·day but 0.2% CNT containing PCL films showed 1.08 g·mm/m²·day. Similarly, the oxygen transmission rate (OTR) of PCL films was found to decrease with the addition of CNT. But, carbon dioxide transmission rate (CO₂TR) of PCL film was improved due to incorporation of CNT. Effect of gamma radiation on PCL films and CNT reinforced PCL‐based composites were also studied. The TS of the irradiated (10 kGy) PCL films gained to 75% higher than control sample. The TS of the 0.2% CNT reinforced composite film was reached to 41 MPa at 15 kGy dose. The barrier properties of non‐irradiated and irradiated (10 kGy) PCL films and composites (0.2% CNT reinforced) were also measured. Both PCL films and composites showed lower values of WVP upon irradiation and indicated better water vapor barrier. The OTR and CO₂TR of the irradiated (10 kGy) PCL films and composites were decreased compared to their counterparts. Surface and interface morphologies of the composites were studied by scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Field dependent temperature shift of dielectric losses peak in TGS

Dielectric constant and loss factor measurements have been performed in triglycine sulfate single crystals at the vicinity of the Curie temperature (T_c≈48.5°C) as a function of ac driving field (20≤v≤10⁶ Hz) in a wide range of field amplitude (50≥E_o≥0.15V/cm). Well defined shifts of loss factor peak (D_max), increasing monotonously with the field, not previously reported as far as we know, were observed and analyzed in terms of the energy dissipated within the vanishing hysteresis loops at T≈T_c corresponding to E_o≈E_c(T), coercive field.     

Effects of Candelilla and Carnauba Wax Incorporation on the Functional Properties of Edible Sodium Caseinate Films

The aim of this study was to evaluate the effects of candelilla (CAN) or carnauba wax (CAR) incorporation on functional properties of edible sodium caseinate (CAS) films. Glycerol and Tween-80 were used as the plasticizer and the emulsifier, respectively. The results showed that the incorporation of waxes increased film opacity, total color differences (∆E), and mechanical resistance and reduced film lightness, water vapor permeability (WVP), and elongation at break. Scanning electron microscopy showed heterogeneous structure of emulsion films with regular distribution of lipid particles. A different internal arrangement was observed as a function of the film composition with both layered and incorporated film structure. Films containing candelilla wax exhibited more regular lipid reorganization, which resulted in better water vapor barrier efficacy and mechanical resistance in comparison to control films. The presence of Tween-80 resulted in better dispersion of lipid particles in film-forming solutions and lower water solubility, lightness, film opacity, and water vapor permeability, whereas the total color differences (∆E) were significantly larger and the improvement in mechanical properties was also achieved.     

Surface analysis and printability studies on electron beam-irradiated thermoplastic elastomeric films from LDPE and EVA blends

The electron beam-initiated surface modification of films prepared from various blends of low-density polyethylene (LDPE), ethylene vinyl acetate (EVA), and ditrimethylol propane tetraacrylate (DTMPTA) was carried out over a range of radiation doses (20-500 kGy) and concentrations of DTMPTA. The films were characterized by Fourier transform infrared-attenuated total reflectance (FT-ATR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle measurements, and peel adhesion. The printability of the films was also measured. FT-ATR and XPS revealed that the surface polarity of the films made from a 50 : 50 blend of LDPE and EVA increased up to a radiation dose of 100 kGy, compared with the unirradiated sample. The polarity decreased after 100 kGy radiation. Surface pitting and roughness were observed in the SEM photomicrographs of the same films, irradiated at higher radiation doses. Higher values of the surface energy were obtained at 100 kGy for the samples without DTMPTA and for the samples containing 3 wt% DTMPTA. Excellent printability was observed for all the films irradiated above an irradiation dose of 20 kGy. The data on the printability and peel adhesion of the irradiated films could be explained by surface energy, XPS, and SEM results.     

EFFECTS OF ASYMMETRIC TEMPERATURE PROFILES ON THERMAL CONVECTION DURING PHYSICAL VAPOR TRANSPORT OF Hg2Cl2

Asymmetric horizontal thermal profiles can change the flow field structure in the physical vapor transport (PVT)of Hg₂Cl₂. It is found that for the ratios of horizontal to vertical thermal Rayleigh numbers Ra_H/Ra ≥ 1·5, the convetive flow structure changes from multicellular to unicellular for the base parametric state of Ra = 2·79 × 10⁴, Pr = 0·91, Le=l·01. Pe = 4·60, Ar= 0·2 and C_r = 1·01. The unicellular flow structure obtained by increasing ∇*_H(Ra_H) is not likely to support the conjecture of the presence of unicellular convective mode in the laser Doppler velocimetry (LDV) experiments for PVT process of Hg₂Cl₂ (Kim el al., 1996). When the six parameters of Ra, Pr, Le, Pe, Ar and C_r are fixed, the dimensional maximum magnitude of the velocity vector |U|_max is proportional to √∇T*_H.     

Improvement of Physicochemical Properties of Rubber Blends Between Nonirradiated and Irradiated Rubber Latexes by Radiation Vulcanization

Abstract

Nonirradiated natural rubber latex (NRL) and irradiated (12 kGy) rubber latex were blended in ratios of 100:0, 85:15, 65:35, 50:50, 35:65, 15:85, and 0:100 (v/v) to improve properties of the rubber latex. The blends were irradiated using different irradiation doses (0–20 kGy) in the presence of a radiation vulcanization accelerator (RVA), normal butyl acrylate (n-BA). The physicochemical properties of the nonirradiated latex, irradiated latex, and blend films were determined after leaching with distilled water. It was observed that the tensile strengths of the blend films increases with an increase in the content of the irradiated proportion and radiation doses. The composition of the blends and the doses of radiation were optimized. The maximum tensile strength (31.41 MPa) was found for the 50:50 composition of the blend with a 5 kGy radiation dose. The 100:0 blends, when irradiated, give the highest tensile strength (27.69 MPa) with 12 kGy but a 15:85 nonirradiated blend gives the tensile strength of 26.18 MPa.     

Antioxidant and physicochemical properties of blended films based on gelatin‐sodium caseinate activated with natural extracts

Blend films of pigskin gelatin (GEL) and sodium caseinate (SCas) with boldo (B), guarana (G), cinnamon (C), or rosemary (R) extracts added were studied. SCas and extracts addition in blend films significantly increased the gloss and better UV barrier of GEL100 films. Extracts incorporation significantly decreased the rigidity and elongation of GEL100 films, which were significantly improved in GEL75:SCas25 blend films with extracts (EM = 295.69 ± 21.75 MPa and EB = 11.60 ± 3.43%). SCas addition not affected the TS parameter. The water vapor permeability of GEL100 films was reduced in blended films with extracts, showing the lowest value for GEL75:SCas25 + R (0.99 ± 0.07 × 10¹⁰ g s^?1 m^?1 Pa^?1). FTIR and microstructure analyses showed good compatibility for all components. The antioxidant activity of GEL100 was significantly increased with SCas and extracts addition (GEL50:SCas50 + R = 4.31 ± 0.11 mM ), suggesting the application of these films as an active food packaging material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44467.     

WATER MIST FLOW IN A SUPERCONDUCTING MAGNET INCLINED AT VARIOUS ANGLES

Water mist (diamagnetic) flow in a superconducting magnet of 10 T at various angles is studied experimentally and numerically. Water mist is produced by ultrasonic atomizers and fed into a cylindrical Plexiglas pipe (inner diameter, 90 mm) placed in a bore space of an inclined superconducting magnet. The water mist is found to stop at some locations in the magnet at inclined angles ψ ≤ π/6. At ψ ≥ π/4, the amount of mist flowing out of the other opening of the pipe increases with an increase in inclined angle. In the computation of this phenomenon, water mist is simulated with 1000 water droplets of 3 μm diameter. Brownian motion is considered and the Langevin equation is solved. The numerical results show that at ψ ≤ π/6, most of the water droplets accumulate above the magnetic coil. However, at ψ ≥ π/4, with an increase in inclined angle, the number of water droplets passing through the magnetic coil increases.     

A STUDY ON VOID FRACTION IN VERTICAL CO-CURRENT UPWARD AND DOWNWARD TWO-PHASE GAS-LIQUID FLOW—I: EXPERIMENTAL RESULTS

An experimental study on void fraction in a small diameter tube (9·525 mm) for vertical upward and downward, gas-liquid, two-phase flow was carried out. Void fraction measurements in water-air were taken for both upward and downward flow using a single beam gamma densitometer. The gamma densitometer was calibrated against the reading from a quick-closing valve system. The experimental results indicate that for V_SL.≥ 1·7 m/s, the void fraction in both upward and downward flow is almost independent of the liquid flow rate. For downward flow and V_SL ≤ 0·1 m/s, the void fraction is independent of the gas flow rate. This corresponds to the flow in the falling film region. In general the void fractions in downward flow were slightly higher than those with upward flow. The experimental data were compared with some correlations and data in the literature. Fairly good agreements (overall relative R.M.S. deviation of 18%) were obtained.     

Novel route of synthesis of Mn---Mg---ferrites using stabilised MnO

Stoichiometric polycrystalline samples of Mn_xMg_1−xFe₂O₄ (0·5 ≤ x ≤ 0·66) have been synthesized by following a novel route using stabilized MnO and Fe₂O₃ at high temperatures. This route precludes the formation of large amounts of Mn³⁺ and Fe²⁺ and precipitation of MgO and -Fe₂O₃ which are generally observed during the usual route of preparation by conventional ceramic techniques. These samples have been characterized for their structural and magnetic properties using X-ray diffraction, Fe⁵⁷ Mössbauer spectroscopy and bulk magnetic properties such as initial permeability, loss factor, ferromagnetic transition temperature, remanance and coercivity. For X = 0·62, these ferrites exhibit the highest remanance ratio 0·96, suitable for square loop applications.     

Influence of Edible Films upon the Moisture Loss and Microstructure of Dietetic Sucrose-Free Sponge Cakes during Storage

The kinetics of changes in the bound water content in dietetic sucrose-free sponge cakes (DC) during storage was investigated. The effect of edible films of polymyxan, pectin, xanthan, and carboxymethylcellulose upon this kinetics was also investigated. The quantitative changes in both states of water (slightly bound water and strongly bound water) were registered by combined dynamic analysis (thermogravimetry analysis, TGA, and differential thermal analysis, DTA). The moisture changes in DC crumb were analyzed by drying out to constant mass. The rate constants were determined according the equation q = q_oe^-kt. The values of rate constants 'k', in day^-1, concerning the different edible films were as follows: for crumb moisture is (8.00 ≤ k ≤ 12.47) × 10^-3, for bound water is (3.07 ≤ k_w ≤ 6.26) × 10^-2, for slightly bound water is (4.22 ≤ k₁ ≤ 8.49) × 10^-2 and for strongly bound water is (2.02 ≤ k₂ ≤ 5.62) × 10^-2 as compared to 18.53 × 10^-3, 7.16 × 10^-2, 9.04 × 10^-2, and 5.36 × 10^-2 in the uncovered DC, respectively. The best water-retaining effect in respect to crumb moisture during storage was ascertained in the use of polymyxan and xanthan films. The lowest rate constant values for bound water and its two states were measured for DC covered with pectin. The relation between the kinetics of both bound water states during storage and ageing of the crumb of DC covered with different edible films and the crumb microstructure was represented. By means of scanning electron microscope was read the smallest change in crumb microstructure of pectin-covered DC on the sixth day of storage.     

Ice formation in hardened cement paste, Part II — drying and resaturation on room temperature cured pastes

Ice formation in partly dried and resaturated room temperature cured mature Portland cement paste has been measured. The measurements were carried out continuously in the temperature range from +20° C to −60° C.

The results demonstrate that the drying-resaturation treatment increases the volume of large pores and the continuity of the pore system. The increase in the volume of large pores occurs at the expense of small pores and necks in the pore system.

As the relative water vapor pressure at which drying takes place is decreased to 0.58, the number of continuous large pores is increased. Drying at lower relative water vapor pressures does not further increase the effect.

The present findings point out the importance of the moisture history of concrete before testing such properties as water permeability and frost resistance.     

ADHESION ENHANCEMENT THROUGH CONTROL OF ACID-BASE INTERACTIONS

Adhesive bond strengths have been determined for lap-shear joints of PS/LLDPE and PS/CPE, a chlorinated version of polyethylene. Joints were formed at temperatures in the range of 180-280°C. In PS/LLDPE, bond strength at lower joining temperatures is compromised by the inability of LLDPE to act as electron acceptor to the donor properties of PS. However, at T ≥ 260°C, PS becomes a fluid capable of interacting through dispersion forces only, leading to enhanced diffusion across the PS/LLDPE interface and much stronger adhesive bonds. An acid-base pairing is in effect in joints of PS/CPE, resulting in strong joints made at T ≤ 240°C. The probable loss of acid-base interaction between the polymers at higher T, coupled with a failure of diffusion across the interface, leads to a lowering of the joint bond strength. Control over interfacial interactions is demonstrated to be a vital factor in the development of adhesive bonds.     

Breakthrough analysis for CO2 removal by activated hydrotalcite and soda ash

Carbon dioxide sorption rate parameters and sorption capacities on two different regenerable sorbents, namely hydrotalcite and activated trona, were investigated in a fixed bed flow adsorber, in the temperature range of 400–527 °C and 80–152 °C, respectively. Hydrotalcite, which was activated at 550 °C, was shown to give total and breakthrough CO₂ sorption capacities as high as 1.16 and 0.70 mmol/g, respectively, at 452 °C, in the absence of water vapor. In the presence of excess water vapor, the total CO₂ sorption capacity was not affected much, however a decrease in the breakthrough capacity and on the sorption rate constant was observed, especially at lower temperatures. In the presence of water vapor, activated trona was shown to give comparable total and breakthrough CO₂ sorption capacities, at much lower temperatures (T < 100 °C). The deactivation model gave good predictions of the CO₂ breakthrough curves and it was successfully used for the evaluation of the adsorption and the deactivation rate constants.     

Influence of preparation conditions on the physical properties of zein films

Zein is a hydrophobic protein produced from maize. Biodegradable zein films without additional reagents were prepared using various controlled drying conditions. The zein films were transparent. Mechanical properties (tensile strength and puncture strength), gas permeability, and water vapor permeability (WVP) of the zein films were measured. The tensile strengths of the zein films were between 7 and 30 MPa and the puncture strengths between 37 and 191 MPa. The zein films had higher oxygen permeability than carbon dioxide permeability. The lowest WVP of the zein film was 0.012×10⁻⁹ g·m/m²·s·Pa. We found differences in the WVP between the sides of the zein films; i.e., the air side of the zein film had a higher WVP than the basal side of the zein film when the films were exposed to high humidity during testing. This indicates a relationship between the WVP of the zein film and the contact angle of the zein film. The mechanical properties of the zein film depended on the drying conditions during preparation. Zein films with various useful physical mechanical properties were produced.     

Effect of crosslinking on the properties of sodium caseinate films

Protein films are used as effective lipid, oxygen, and aroma barriers at moderate relative humidity conditions. However, they perform poorly as moisture barriers. The introduction of crosslinks within or between protein chains by enzymatic or chemical modification has been proposed as an alternative means to achieving a stronger polymeric matrix structure, which would result in better functional film properties. In this article, we report the preparation and characterization of sodium caseinate (SC) films crosslinked by glutaraldehyde (GTA) or heat. The crosslinking density increased with GTA content. The thermal stability and tensile modulus and strength increased with GTA content, although films with a low crosslinking density exhibited lower properties than the uncrosslinked sample. Unexpectedly, water vapor permeability and absorption also increased with crosslinking density. The crosslinking of SC was also induced by simple heating. The resulting films showed enhanced thermal, mechanical, and barrier properties compared to the unmodified SC films and even the GTA‐crosslinked samples. GTA crosslinking was unable to reduce the high hydrophilicity of the SC films. Thermally induced crosslinking was revealed to be a valid alternative for improving the properties of SC films, without the inherent complications associated with the use of a chemical crosslinking agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microstructure and properties of porous nanocomposite films: effects of composition and process parameters

Porous nanocomposite films based on polypropylene (PP) and titanium dioxide (TiO₂) nanoparticles were prepared by melt extrusion followed by uniaxial stretching. The effects of drawing temperature, extension rate, stretching ratio and composition of the base films on the final properties and microstructure of the stretched films were studied. Water vapor permeability (WVP) results showed a significant decrease in permeability of the films stretched at temperatures higher than 60 °C. Porosity, pore size and water vapor transmission rate in the porous nanocomposite films had a direct relation with nanoparticle content, extension rate and stretching ratio. Study of the morphology of the stretched films, using SEM, revealed that the pores form due to PP/TiO₂ interfacial debonding at low stretching ratios. Higher stretching ratios cause an enlargement of the pores and the formation of a PP fibril structure parallel to the stretching direction. Quantification of dye adsorption revealed that the quantity of adsorbed dye increased with porosity and surface area of the pores. © 2014 Society of Chemical Industry