Characterization of chitosan/caseinate films

Films made from sodium caseinate and/or chitosan, using glycerol as plasticizer, were prepared by casting from aqueous solutions. Films cryo‐fractured surfaces were examined by SEM. FTIR spectra of the chitosan/caseinate films showed an increase in the intensity of the amide band, corresponding to the strong interactions developed by the polyelectrolytic complexation of both components. Addition of 28 wt% of glycerol to caseinate films, conditioned at 50% relative humidity (RH), reduced the modulus from 2908 to 250.9 MPa, while the ultimate elongation increased from 4 to 63.2%. Increment to 80% RH further reduced the modulus down to 52.8 MPa. Similar results were found for the glycerol plasticization of chitosan films. The complex films showed a moderate improvement of the tensile strength (19.6 MPa) and an increase of the impact strength (35.6 GPa) with respect to those corresponding of chitosan films (17 MPa and 26.6 GPa, respectively). These properties were markedly improved with respect to those of caseinate (6.2 MPa and 13.4 GPa, respectively). The interactions developed between the cationic polymer chitosan, and the Na‐caseinate carboxyl groups, lead to polyelectrolyte complexation in forming the film, which is proposed as the reason for improvement with respect to caseinate or chitosan films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Water vapor barrier and mechanical properties of konjac glucomannan–chitosan–soy protein isolate edible films

The effects of polymer composition, glycerol concentration and pH of film-forming solution on water vapor permeability (WVP), tensile strength (TS) and percentage elongation at break (%E) of composite edible film based on konjac glucomannan (KGM), chitosan and soy protein isolate (SPI) were investigated. Of the plasticizers tested, glycerol was found to be a suitable plasticizer regarding mechanical properties and WVP. The WVPs of the films were determined to be (3.29–9.63) × 10^?11 g m^?1 s^?1 Pa^?1, TS between 16.77 and 51.07 MPa, and %E between 1.29% and 10.73%, depending on film composition. Incorporation of SPI to the polymer matrix decreased both WVP and mechanical properties. Increase in both glycerol concentration and the pH of film-forming solution decreased WVP and TS but increased %E. The results suggest that film composition and the pH of film-forming solution are the major factors influencing the film properties.     

Properties of chitosan‐based biopolymer films with various degrees of deacetylation and molecular weights

An increase in the depolymerization of chitosan was found with an increased concentration of sodium perborate. Acetic anhydride was added to reacetylated chitosan in a molar ratio per gulcosamine unit, and the amide I band of IR spectra changed with the addition of acetic anhydride. Sixteen chitosans with various molecular weights (MWs) and degrees of deacetylation (DODs) were prepared. X‐ray diffraction patterns indicated their amorphous and partially crystalline states. Increases in the chitosan MW and DOD increased the tensile strength (TS). TS of the chitosan films ranged from 22 to 61 MPa. However, the elongation (E) of chitosan films did not show any difference with MW. TS of chitosan films decreased with the reacetylation process. However, E of chitosan films was not dependent on DOD. The water vapor permeabilities (WVPs) of the chitosan films without a plasticizer were between 0.155 and 0.214 ng m/m² s Pa. As the chitosan MW increased, the chitosan film WVP increased, but the values were not significantly different. Moreover, the WVP values were not different from low DOD to high DOD. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3476–3484, 2003     

Effects of the incorporation of saturated fatty acids on the mechanical and barrier properties of biodegradable films

The effects of saturated fatty acids at a concentration of 1.5% on the mechanical and barrier properties of starch‐based films were evaluated in films prepared with two concentrations of glycerol, 20 and 25%. The water vapor permeability (WVP) was determined at three ranges of relative humidity, RH, (0–33, 33–64 and 64–97%). In all cases, an increase in WVP values was observed with increasing RH. SEM images showed a more homogeneous and compact structure in the films with caproic and lauric acids. The films with fatty acids showed higher elongation and maximum stress, and they had Young's modulus values close to those of the control; thus, the addition of fatty acids did not impair the mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical properties and water vapor permeability of thin film from corn hull arabinoxylan

Isolated corn hull arabinoxylan was dissolved in water and provided a clear solution. Plasticizer (glycerol, propylene glycol, or sorbitol) was added to the arabinoxylan solution at 0–20 wt % (film dry weight), which was cast into stable films. Film thickness ranged from 22 to 32 μm. Mechanical properties, moisture content, and water vapor permeability (WVP) were studied for the arabinoxylan‐based films as a function of plasticizer concentration. Measured data for the corn hull arabinoxylan–based films were 13–18 wt % moisture content, 10–61 MPa tensile strength, 365–1320 MPa modulus, 6–12% elongation, and 0.23–0.43 × 10^?10 g m^?1 Pa^?1 s^?1 water vapor permeability. Plasticized arabinoxylan films produced in this study had lower WVPs than those of unplasticized films, which is likely attributable to the phenomenon known as antiplasticization. Scanning electron micrographs showed a homogeneous structure on film surfaces. Films containing sorbitol had the best moisture barrier properties. When grapes were coated with arabinoxylan and arabinoxylan/sorbitol films, weight loss rates of the fruit decreased by 18 and 41%, respectively, after 7 days. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2896–2902, 2004     

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 .     

Films from oat spelt arabinoxylan plasticized with glycerol and sorbitol

The development of packaging films based on renewable materials is an important and active area of research today. This is the first extensive study focusing on film‐forming properties of an agrobiomass byproduct, namely, oat spelt arabinoxylan. A plasticizer was needed for cohesive film formation, and glycerol and sorbitol were compared. The tensile properties of the films varied with the type and amount of the polyol. With a 10% (w/w) plasticizer content, the films containing glycerol had higher tensile strength than the films containing sorbitol, but with a 40% plasticizer content, the result was the opposite. Sorbitol‐plasticized films retained their tensile properties better than films with glycerol during 5 months of storage. The films were semicrystalline with similar crystallinity indices of 0.20–0.26. The largest crystallites (9.5 nm) were observed in the film with 40% glycerol. The softening of films with 40% (w/w) glycerol started at a significantly lower relative humidity (RH) than that of the corresponding sorbitol‐containing films. The films with sorbitol also had lower water vapor permeability (WVP) than the films with glycerol. The films plasticized with 10% (w/w) sorbitol had a WVP value of 1.1 g mm/(m²·d·kPa) at the RH gradient of 0/54%. The oxygen permeability of films containing 10% (w/w) glycerol or sorbitol was similar: 3 cm³·μm/(m²·d·kPa) at 50–75% RH. A higher plasticizer content resulted in more permeable films. Permeation of sunflower oil through the films was not detected. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Gas barrier and wetting properties of whey protein isolate‐based emulsion films

The aim of this research was to investigate the effect of rapeseed oil concentration (1–3% w/w) on the water vapor, oxygen and carbon dioxide permeability, water vapor sorption and surface properties of whey protein isolate emulsion‐based films. The water contact angle as affected by oil content, film side and time was analyzed. The effect of temperature (5 and 25°C) on the water vapor permeability (WVP), water vapor sorption kinetics and diffusion coefficient was also studied. The results showed that the incorporation of a lipid phase to whey protein film‐forming solutions was able to decrease the WVP, water hydrophilicity (increasing water contact angle) and water transfer of whey protein films. However, the films containing oil were more permeable to oxygen and carbon dioxide. Significantly higher values of WVP and diffusion coefficient were obtained at 5°C than at 25°C, indicating that storage temperature should be taken into account when designing the composition of edible films and coatings for food applications. POLYM. ENG. SCI., 59:E375–E383, 2019. © 2018 Society of Plastics Engineers     

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 .     

Effect of Drying Conditions on the Mechanical and Barrier Properties of Films Based on Chitosan

Films plasticized with glycerine were prepared using chitosan with two different molecular weights (Mw), 780 and 430 kDa. Films were obtained by drying at 80 and 40°C at 20 and 40% relative humidity (RH) in a climatic chamber. Drying kinetics were established by the measurement of the evolution of the actual temperatures of the film forming solutions. Chitosan Mw did not show any significant influence on drying kinetics. Drying temperature affected drying kinetics in a more intense way than drying RH. Maximum tensile strength (86 MPa) and elongation at break (56.5%) were obtained with slow drying cycles (lower drying T) and when higher Mw chitosan was employed. Minimum water vapor permeability (0.59 g · mm/kPa · h · m) was achieved for films dried at faster drying cycles (higher drying T). Chitosan Mw was not a significant factor affecting water vapor permeability.     

Water vapor permeability properties of edible whey protein-lipid emulsion films

The water vapor permeability (WVP) of whey protein emulsion films was investigated. The exponential effect of relative humidity on the WVP of whey protein films was reduced through lipid incorporation. Film orientation had a significant effect on WVP due to emulsion separation during film formation. Heat denaturation of whey proteins lowered emulsion film WVP. Increasing fatty acid and fatty alcohol chainlengths significantly reduced WVP, as did increasing lipid concentration. The WVPs of fatty acids, fatty alcohols and beeswax were compared in whey protein-lipid emulsion films. Scanning and transmission electron microscopy revealed the crystalline microstructure of lipid particles in emulsion films.     

Moisture sorption/desorption behavior of various manmade cellulosic fibers

The kinetics of dynamic water vapor sorption and desorption on viscose, modal, cotton, wool, down, and polyester fibers and lyocell knit fabrics were investigated according to the parallel exponential kinetics (PEK) model. The total equilibrium moisture regain (M_inf(total)) in all the materials decreased with increasing temperature. However, the partial equilibrium fast sorption, determined by PEK simulation at 60% relative humidity (RH) and 36°C, was larger than that at 20°C, whereas the partial equilibrium slow sorption was smaller. The characteristic times in fast sorption (τ₁) and in slow sorption (τ₂) for lyocell were reduced when the conditions were changed from 60% RH and 20°C to 36°C, whereas those for the other fibers increased. Lyocell exhibited the highest M_inf(total) value and the lowest τ₁ and τ₂ values, and this suggested high equilibrium moisture content and fast moisture uptake/release, that is, high moisture accessibility for lyocell. The relationships between the moisture regain, hysteresis, water retention capacity, and Brunauer–Emmett–Teller surface volume in the materials were also examined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1621–1625, 2005     

Edible starch sodium octenyl succinate film formation and its physical properties

Edible starch sodium octenyl succinate (SSOS) films, with or without glycerol as plasticizer, were prepared by solution‐casting method. The effect of SSOS concentration, degree of substitution (DS) of octenyl group, as well as glycerol content, on the properties of SSOS films was studied including tensile strength, water vapor permeability (WVP), and oil permeability (OP). The results indicated that the tensile strength of SSOS film was up to 39.4 ± 1.9 MPa when the concentration of SSOS was 0.05 g/mL and DS was 0.05. The increase of glycerol content resulted in a decrease of film tensile strength. WVP of SSOS films was relatively low. Meanwhile, study in OP showed that SSOS films were oilproof. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Heterogeneous method of chitosan film preparation: Effect of multifunctional acid on film properties

The heterogeneous crosslinking method was applied to chitosan films with citric acid to observe and understand the effect of a multifunctional acid at a low concentration on film properties. Neat and neutralized chitosan films and films containing 15% (w/w) citric acid (denoted as CA films) were characterized by mechanical, water vapor permeability (WVP), and thermogravimetric analysis tests. The CA films displayed a higher tensile strength by 10%, lower WVP by 30%, and higher thermal stability, compared to neutralized films. The crystalline structure converted back from tendon to Type II after the addition of citric acid, as determined by X-ray diffraction. Neat films displayed a lower water contact angle (72°) compared to neutralized and CA films (78°–79°). The heterogeneous method was also applied to incorporate a plasticizer into a neutralized film to potentially observe the glass transition using dynamic mechanical analysis. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48648.     

Irradiated sodium–alginate/poly(ethylene oxide) blend films improved by methyl acrylate monomer

Sodium alginate (SA)‐based poly(ethylene oxide) (PEO) blend films were improved by methyl acrylate (MA) monomer and γ irradiation toward practical application. The films were prepared by a casting method and modified by glycerol (Gol) and mustard oil (MO). The SA‐based films were successfully produced with γ irradiation (12 kGy) with 10% PEO, 15% Gol, 20% MO, and 7% MA on a mass basis as optimized. The tensile strength (TS), tear strength (TT), elongation at break (EB), Young's modulus, moisture content, water vapor permeability (WVP), and structural properties of the blended films were determined. The thermal properties of the films were characterized by thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry, and the structural features were examined with Fourier transform infrared spectroscopy. The ultimate results of this study show a rather remarkable enhancement in the tensile properties (30% TS and 67% TT) and reduction in EB (40%) of the SA‐based films with MA addition and γ irradiation. The as‐prepared SA‐based films demonstrated considerable reductions in the moisture content and WVP and also conferred a desired stability of the films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43562.     

The water vapor sorption behavior of a galactomannan cellulose nanocomposite film analyzed using parallel exponential kinetics and the Kelvin–Voigt viscoelastic model

Nanocomposite films have been developed where a galactomannan (guar) matrix was reinforced with cellulose nanowhiskers and plasticized using sorbitol. The properties of these films were compared with films made from guar only. The films were examined using scanning electron microscopy and dynamic vapor sorption. The sorption kinetics properties were analyzed using parallel exponential kinetics (PEK) and this data interpreted using the Kelvin‐Voigt (K‐V) viscoelastic model. Substantial differences in sorption behavior were noted between the guar and cellulose reinforced guar films. Addition of cellulose nanowhiskers (CNWs) to the guar resulted in a change in the shape of the isotherm, as well as a reduced equilibrium moisture content throughout the hygroscopic range. With the guar film, hysteresis between the adsorption and desorption branches of the isotherm occurred up to 75% RH, where it collapsed. Dynamic mechanical analysis showed that the collapse of the hysteresis loop occurred at the glass transition temperature of the guar film. However, addition of CNWs to the guar produced a film where sorption hysteresis was found to occur throughout the hygroscopic range. The applicability of the K‐V interpretation of the sorption kinetics is discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Comparative Evaluation of Physical Properties of Edible Chitosan Films Prepared by Different Drying Methods

Edible films are alternative packaging, which have recently received much attention due mainly to environmental reasons. Edible films may be formed from edible biomaterials such as polysaccharides, proteins, or lipids. Among these biopolymers, chitosan is of interest because it has a good film-forming property and is biodegradable, biocompatible, and nontoxic. Several techniques have been used to prepare edible chitosan films with various degrees of success. However, it is always interesting to find an alternative technique to produce films of superior quality at shorter processing (drying) time. In this study, the influences of different drying methods and conditions on the drying kinetics and various properties of chitosan films were investigated. Drying at control conditions (ambient air drying and hot air drying at 40°C) as well as vacuum drying and low-pressure superheated steam drying (LPSSD) at an absolute pressure of 10 kPa were carried out at different drying temperatures (70, 80, and 90°C). The properties of chitosan films, in terms of color, tensile strength, percent elongation, water vapor permeability (WVP), glass transition temperature (T _g ), and crystallinity, were also determined. Based on the results of both the drying behavior and film properties, LPSSD at 70°C was proposed as the most favorable conditions for drying chitosan films.     

Sorption and transport of water vapor in nylon 6,6 film

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 ≈ 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 N H groups. However, an increase was seen for the CO groups. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 197–206, 1999     

Water-swelling behavior of an ethylene–vinyl alcohol copolymer in the presence of sorbed sodium chloride

The swelling behavior of water in a poly(ethylene–vinyl alcohol) copolymer (70 mol % vinyl alcohol) has been characterized at 25°C by vapor and liquid sorption experiments over a range of water activities. The activity of the vapor phase has been varied by incrementing the pressure of the water vapor in the sorption cell. Alternatively, for the liquid phase experiments, aqueous sodium chloride solutions of different concentrations have been used to vary systematically the activity of the water in the salt solution and to introduce various concentrations of salt into the copolymer films. Relaxation-controlled sorption and Fickian diffusion have been observed as limiting cases of the water sorption behavior at high and low water activities, respectively. The effects of sorbed sodium chloride on water vapor sorption kinetics and equilibria were determined independently. A second salt phase forms within the previously homogeneous and seemingly single phase polymeric system, upon contacting the salt-loaded film with a water vapor activity above a threshold value corresponding to the activity of water in the salt solution used to introduce the salt into the films. The water and salt solubilities in the ethylene–vinyl alcohol copolymer have been measured systematically to describe the complex sorption equilibria associated with this three-component, multiphase system.     

Aging properties and hydrophilicity of maize starch plasticized by hyperbranched poly(citrate glyceride)

Hyperbranched poly(citrate glyceride)s (HBPETs) as plasticizers were mixed with maize starch (S) via cooking and film formation. The structure, aging properties, and hydrophilicity of the plasticized starches were studied by means of Fourier transform infrared spectroscopy, X-ray diffraction, tension testing, contact angle testing, solubility measurements, moisture absorption, and water vapor permeability (WVP). Compared with a glycerol–S plasticized film, the HBPET–S composite films had better mechanical properties in terms of both strength and elongation at break, better aging resistance, less moisture absorption, less WVP, and more hydrophobicity on the film surface. The mechanisms behind the performances resulted from stronger and more stable H bonds between the abundant active end groups of HBPET and hydroxyls of starch and the high branching degree of the HBPETs; this was helpful for effectively inhibiting the recrystallization of starch. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46899.