ABSTRACT:The sorption and transport of water in nylon 6,6 films as functions of the relative humidity (RH) and temperature were studied. Moisture-sorption isotherms determined gravimetrically at 25, 35, and 45°C were described accurately by the GAB equation. Water-vapor transmission rates were enhanced above Ϸ 60 -70% RH, primarily due to the transition of the polymer from glassy to rubbery states. The glass transition temperatures (T g 's) of nylon 6,6 were measured at various moisture contents using differential scanning calorimetry. The results showed that the sorbed water acted as an effective plasticizer in depressing the T g of the polyamide. Fourier transform infrared spectroscopy (FTIR) was utilized to characterize the interaction of water and the nylon. Evidence from FTIR suggested that the interaction of water with nylon 6,6 took place at the amide groups. Based on the frequency shift of the peak maxima, moisture sorption appeared to reduce the average hydrogen-bond strength of the NOH groups. However, an increase was seen for the CAO groups.

Whey protein isolate (WPI)-based edible biopolymer films were prepared using a film-forming stage designed to provide heat-induced gelation. Effects of whey-protein ratios, calcium, glycerol (plasticizer), and emulsion droplet incorporation on film tensile and barrier properties were investigated. Protein ratios had less influence on tensile strength, elongation, and water vapor permeability than glycerol and calcium ion concentrations. Semitransparent films with reasonably high tensile and UV-light barrier properties and moderate water vapor barrier properties were prepared from WPI:20% glycerol:10 mM calcium solutions. Microstructure analysis revealed the influence of glycerol and calcium concentrations on gel networks, which could be related to film tensile properties.

ABSTRACT:The transport properties of oxygen and water vapor through EVOH films as functions of relative humidity (RH) and temperature were studied. The results of oxygen and water vapor permeation demonstrated that temperature and RH markedly affected barrier properties of these films. In general, the EVOH films had minimal oxygen and water vapor permeabilities at a low RH, attributed to the reduced mobility of the polymer resulting from strong interactions between small water molecules and the polymeric matrix at low RH. Beyond 75% RH, the permeabilities increased considerably. In addition, the barrier performance of the EVOH films was found to be dependent on their ethylene content and orientation. From the experimental data, semiempirical equations describing oxygen transmission rates (O 2 TR) as functions of RH and temperature were developed.

Moisture sorption kinetics of nonoriented ethylene vinyl alcohol copolymer (EVOH) film (EF‐E15) were studied at 25, 35, and 45°C. Anomalous diffusion was observed for the polymeric film at high relative humidities (RH) and higher temperatures. Diffusion and solubility coefficients of water were found to be concentration dependent. The moisture sorption isotherms of three types of EVOH films (EF‐E15, EF‐F15, and EF‐XL15) determined at 25, 35, and 45°C, were well described using the GAB equation. Glass transition temperatures (Tg) of the EVOH films, as influenced by RH, were measured using differential scanning calorimetry. Tg values decreased with increasing RH due to the plasticization effect of water, and were found to be dependent on ethylene content and orientation of the EVOH films. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 691–699, 1999

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ABSTRA ABSTRA ABSTRA ABSTRA ABSTRACT CT CT CT CT: A : A : A : A : Apple and or pple and or pple and or pple and or pple and orange juices packed in poly ange juices packed in poly ange juices packed in poly ange juices packed in poly ange juices packed in polyester bottles w ester bottles w ester bottles w ester bottles w ester bottles wer er er er ere stor e stor e stor e stor e stored in dar ed in dar ed in dar ed in dar ed in dark, intense fluor k, intense fluor k, intense fluor k, intense fluor k, intense fluorescent (1500 lux), escent (1500 lux), escent (1500 lux), escent (1500 lux), escent (1500 lux), and UV light conditions in temperature-controlled (22 °C) chambers and monitored more than 7 mo for ascorbic and UV light conditions in temperature-controlled (22 °C) chambers and monitored more than 7 mo for ascorbic and UV light conditions in temperature-controlled (22 °C) chambers and monitored more than 7 mo for ascorbic and UV light conditions in temperature-controlled (22 °C) chambers and monitored more than 7 mo for ascorbic and UV light conditions in temperature-controlled (22 °C) chambers and monitored more than 7 mo for ascorbic acid content and color changes acid content and color changes acid content and color changes acid content and color changes acid content and color changes. P . P . P . P . Poly oly oly oly olyester bev ester bev ester bev ester bev ester bever er er er erage bottles w age bottles w age bottles w age bottles w age bottles wer er er er ere made of poly e made of poly e made of poly e made of poly e made of polyethylene ter ethylene ter ethylene ter ethylene ter ethylene terephthalate (P ephthalate (P ephthalate (P ephthalate (P ephthalate (PET ET ET ET ET), or P ), or P ), or P ), or P ), or PET ET ET ET ET blended with 0.25%, 1%, and 4% polyethylene naphthalate (PEN). The cut-off wavelength ranged from 322 nm for blended with 0.25%, 1%, and 4% polyethylene naphthalate (PEN). The cut-off wavelength ranged from 322 nm for blended with 0.25%, 1%, and 4% polyethylene naphthalate (PEN). The cut-off wavelength ranged from 322 nm for blended with 0.25%, 1%, and 4% polyethylene naphthalate (PEN). The cut-off wavelength ranged from 322 nm for blended with 0.25%, 1%, and 4% polyethylene naphthalate (PEN). The cut-off wavelength ranged from 322 nm for P P P P PET to 373 nm for the 4% P ET to 373 nm for the 4% P ET to 373 nm for the 4% P ET to 373 nm for the 4% P ET to 373 nm for the 4% PEN/P EN/P EN/P EN/P EN/PET blend. S ET blend. S ET blend. S ET blend. S ET blend. Spectr pectr pectr pectr pectral irr al irr al irr al irr al irradiance adiance adiance adiance adiance, visible light intensity , visible light intensity , visible light intensity , visible light intensity , visible light intensity, and light distr , and light distr , and light distr , and light distr , and light distribution w ibution w ibution w ibution w ibution wer er er er ere e e e e evaluated in the light chambers and compared with supermarket display lighting and outdoor daylight conditions. evaluated in the light c...

: Influences of rigid (glass) and deformable (gellan) particles dispersed in gellan gels were studied to better understand the effect of structure on the rheological properties of model composite foods. Composites with inclusions at 0%, 10%, 20%, and 30% volume fractions (VF) were tested under small deformation oscillatory shear. In gels containing rigid particles, the dynamic shear storage modulus (G′) decreased initially, exhibited a minimum around 20% VF, then increased at 30% VF behavior that was attributed to physical interactions among particles. In gels containing deformable particles, the linear decrease in G′ with increasing VF may be due to particle compliance under stress or to particle separation from the matrix, thereby causing gel weakening.

Moisture sorption kinetics of nonoriented ethylene vinyl alcohol copolymer (EVOH) film (EF-E15) were studied at 25, 35, and 45°C. Anomalous diffusion was observed for the polymeric film at high relative humidities (RH) and higher temperatures. Diffusion and solubility coefficients of water were found to be concentration dependent. The moisture sorption isotherms of three types of EVOH films (EF-E15, EF-F15, and EF-XL15) determined at 25, 35, and 45°C, were well described using the GAB equation. Glass transition temperatures (T g ) of the EVOH films, as influenced by RH, were measured using differential scanning calorimetry. T g values decreased with increasing RH due to the plasticization effect of water, and were found to be dependent on ethylene content and orientation of the EVOH films.