Packaging‐related properties of alkyd‐coated,wax‐coated,and buffered chitosan and whey protein films

Packaging‐related properties of coated films of chitosan–acetic acid salt and whey protein concentrate (WPC) were studied. Chitosan (84.7% degree of deacetylation) and WPC (65–67% protein) were solution cast to films. These films are potential oxygen barriers for use in packaging. Coatings of wax or alkyds were used to enhance the water‐barrier properties. The packaging‐related properties of chitosan films treated in a buffering solution, with a pH of 7.8, were also investigated. The coated films were characterized with respect to Cobb absorbency, overall migration to water, water vapor transmission rate, and oxygen permeability. The creasability and bending toughness were determined. The wax was a more efficient barrier to liquid water and 90–95% relative humidity than the alkyd. However, the alkyd‐coated material had superior packaging‐converting properties. The alkyd‐coated WPC and chitosan–salt films were readily folded through 180° without any visible cracks or delamination. The overall migration from the alkyd‐coated materials was below the safety limit, provided the coat weight was higher than 7.5 mg/cm² on WPC and 2.1 mg/cm² on chitosan–salt. The barrier properties of chitosan film under moist conditions were improved by the buffer treatment. However, the buffering also resulted in shrinkage of the film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 60–67, 2004     

Barrier properties and abrasion resistance of biopolymer‐based coatings on biodegradable poly(lactic acid) films

Coated polylactic acid (PLA) films consisting of crosslinked‐chitosan/beeswax layer were prepared to improve barrier properties and abrasion resistance of the base substrate. The effect of crosslinking the chitosan layer on durability and barrier properties of the coatings was investigated. Crosslinked samples exhibited lower degree of swelling compared to uncrosslinked samples and 50% reduction in water vapor transmission rate (WVTR) compared to neat PLA films. The beeswax coating decreased the WVTR of chitosan‐coated PLA films significantly (by 100%). However, it had a marginal effect on the oxygen transmission rate. Water vapor transmission was less affected by abrasion than oxygen transmission for both uncrosslinked and crosslinked samples. The WVTR of crosslinked samples were retained even after being subjected to abrasion, whereas WVTR of uncrosslinked samples dropped by 50%. Results obtained using the Taber test method also show that the weight loss of crosslinked coatings are about 75% less than that of uncrosslinked samples and can withstand a greater number of cycles before rupture. These translucent‐coated films retained good barrier and mechanical properties along with providing improved abrasion resistance after crosslinking. This approach provides exciting new possibilities for expanding the use of biodegradable polymers in packaging applications. POLYM. ENG. SCI., 59:1874–1881, 2019. © 2019 Society of Plastics Engineers     

Physical and mechanical properties of nanocomposite barrier film containing encapsulated nanoclay

Waterborne poly(styrene‐co‐butyl acrylate) was prepared via miniemulsion polymerization in which nanoclay (Cloisite® 30B, modified natural MMT) in different concentrations was encapsulated. Scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy confirmed the encapsulation and intercalated‐exfoliated structure of Cloisite® 30B within poly(styrene‐co‐butyl acrylate). The effect of nanoclay content on water vapor permeability, water uptake, oxygen permeability, thermal, and mechanical properties of thin films containing 1.5, 2.56, 3.5, and 5.3 wt % encapsulated Cloisite® 30B in poly(styrene‐co‐butyl acrylate) was investigated. The presence of encapsulated Cloisite® 30B within the polymer matrix improved tensile strength, Young's modulus, and toughness of the nanocomposites depending on the nanoclay content. Water vapor transmission rate, oxygen barrier properties, and thermal stability were also improved. The results indicated that the incorporation of Cloisite® 30B in the form of encapsulated platelets improved physicomechanical properties of the nanoclay‐polymer composite barrier films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and barrier properties of poly(lactic acid) films coated by nanoclay–ink composition

In this study, poly(lactic acid) (PLA) films were coated by an ink formulation containing nanoclay dispersed with ultrasonic homogenization for 20 min. Mechanical and barrier properties of the coated films were evaluated according to clay type and concentration. PLA films coated by ink formulations containing Cloisite 30B displayed the best mechanical and barrier properties in six types of nanoclays. PLA films coated by Cloisite 30B‐containing ink varying in clay concentration were investigated. Tensile strength and elongation at break of these coated films were improved in 1% Cloisite 30B. Oxygen permeability decreased significantly upon the addition of clay levels up to 1% and slightly decreased with further increases in the amount of the clay. The value of water vapor permeability also decreased depending on the increases of clay (0%–20%). When the clay content in the sample was 2.0%, the surface of coated PLA films displayed aggregation visible using film emission scanning electron microscopy. X‐ray diffractometry and transmission electron microscopy indicated that a mixture of exfoliated and intercalated structure was formed with addition of 1% (w/w) Cloisite 30B to the ink after ultrasonication. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface and barrier properties of hybrid nanocomposites containing silica and PEO segments

Hybrid organic–inorganic nanocomposites containing PEO segments linked to a methacrylate network were prepared through a dual‐curing process, which involved photopolymerization and condensation of alkoxysilane groups. A system based on an α,ω‐dimethacrylate PEO oligomer (BEMA 1400) added with methacryloyl‐oxypropyl‐trimethoxysilane (MEMO) and tetraethoxysilane (TEOS) was used. The surface properties of the obtained films were investigated through XPS analyses and contact angle measurements. A selective enrichment of the MEMO additive towards the outermost layers of the films was evidenced either in the presence or in the absence of TEOS. SEM analyses were performed on the cross section of the films coated on PET substrates, determining the film composition at different depth by EDS analysis. The Si content was found constant, moving from the PET surface towards the air–surface of the films. The barrier properties, with respect to oxygen, of the hybrid films coated on a PET substrate were measured. A decrease of the permeability and of the oxygen transmission rate using hybrid coatings was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4107–4115, 2007     

Barrier properties of poly(lactic acid)/cloisite 30B composites and their relation between oxygen permeability and relative humidity

Poly(lactic acid) based nanocomposite films were prepared by melt compounding and subsequent flat film extrusion. After characterizing the nanocomposites with the help of transmission electron microscopy and wide angle X‐ray diffraction to estimate the nanoclay distribution in the matrix material, the oxygen and water vapor permeability of untreated and annealed nanocomposite films were analyzed. A reduction to 34% of both permeability values could be realized by the addition of 6 wt % Cloisite 30B and subsequent annealing to realize maximum crystallinity. Experimental permeability as a function of nanoclay concentration was successfully described by the Tortuous Path Model. In addition, the correlation between oxygen permeability and relative humidity was analyzed for pure PLA and PLA based nanocomposite films. For both untreated films oxygen permeability decreased almost linearly between 0% and 96% RH to approximately 70% of the respective value for the dry sample. Annealed PLA films, on the other hand, showed a similar behavior up to 70% RH but an increase in oxygen permeation for higher moisture content. This is explained by the observed reduction in crystallinity generating more free volume, bringing the system closer to the amorphous case where permeability is generally higher. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44424.     

Synthesis of flame retardant polyester‐urethanes and their applications in nanoclay composites and coatings

This paper describes the synthesis of phosphorus‐containing polyester‐urethanes and their applications in nanoclay composites and coatings. Polyester was prepared by the reaction of bis(bisphenol‐A) monophenyl phosphonate, maleic anhydride and phthalic anhydride. The polyester was reacted with various diols such as ethylene glycol, diethylene glycol and propylene glycol to obtain polyester polyols. Synthesized polyester polyols were characterized by chemical analysis and instrumental analysis and was used further to react with different isocyanates to develop polyester‐urethanes. The synthesized polyester‐urethanes were blended with organo‐modified montmorillonite nanoclay (1 wt%, 3 wt% and 5 wt%) and were cast in a mold and coated on mild steel panels. The thermal stability of neat polyester‐urethane and the nanoclay composites was determined by thermogravimetric analysis. The flame retardant properties of cast films and their composites were determined by the limiting oxygen index and UL‐94 test methods. The physical and mechanical properties of coatings such as pot life, drying properties, scratch hardness, pencil hardness, impact resistance, adhesion and flexibility were investigated. The chemical resistance properties of the coatings were also determined in different reagents. The data reveal that the polyester‐urethane nanoclay composites with 3 wt% clay hold promise for use in effective flame retardant coatings. © 2013 Society of Chemical Industry     

Film formation and surface properties of enzymatically crosslinked casein films

The use of renewable materials as barrier material is currently intensively investigated. Biopolymers such as polysaccharides, lipids, and proteins have been studied as barrier materials. Protein‐based films often possess good gas barrier properties, but because of their hydrophilic nature the gas barrier properties are sensitive to humidity. The improvement of the properties of sodium caseinate barrier films in potential packaging applications was studied by investigating the effects of enzymatic treatment and plasticizer on the film properties. Oxidoreductases Trametes hirsuta laccase (ThL) and Trichoderma reesei tyrosinase (TrTyr) were compared with transglutaminase for crosslinking of the sodium caseinate molecules in the films and coatings. All of the studied enzymes were able to crosslink sodium caseinate. Film solubility tests, protein electrophoresis, contact angle measurements, and atomic force microscopy studies showed that TrTyr treatment results in sodium caseinate films and coatings with better overall properties compared to treatment with ThL. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrophobicity and Water Vapor Permeability of Ethylene-plasma-coated Whey,Chitosan and Starch Films

Abstract

Water vapor transmission rate was measured on uncoated and ethyfeae-plasma-coated whey (65-93.5% whey protein), on chitosan and starch films and on aluminum-coated chitosan. Surface hydrophobicity was assessed by contact angle measurements, and X-ray photoelectron spectroscopy was used to characterize the coatings. The water vapor transmission rate through the uncoated polymer films was highest for starch and lowest for chitosan. Whey showed intermediate water permeability, with the sample containing 65% whey-protein having the lowest water vapor transmission rate. An improvement in water vapor barrier properties was observed only for the aluminum-coated sample and not for any of the polyethylene-coated samples. It is observed that the penetrating water caused the substrate to swell and the polyethylene coating layer to crack. According to profilometry, the thickness of the polyethylene coating layer was 0.1-1 μm after 15 min exposure time. The coating was hydrophobic and contained almost exclusively carbons typical of linear or crosslinked hydrocarbons. It is suggested that the observed decrease in hydrophobicity with time during the contact angle measurements is due to the reorientation at the surface of carbonyls present in small amounts in the coating.     

Oxygen barrier coating deposited by novel plasma‐enhanced chemical vapor deposition

We report the use of a novel plasma‐enhanced chemical vapor deposition chamber with coaxial electrode geometry for the SiO_x deposition. This novel plasma setup exploits the diffusion of electrons through the inner most electrode to the interior samples space as the major energy source. This configuration enables a gentle treatment of sensitive materials like low‐density polyethylene foils and biodegradable materials. SiO_x coatings deposited in the novel setup were compared with other state of the art plasma coatings and were found to possess equally good or better barrier properties. The barrier effect of single‐layer coatings deposited under different reaction conditions was studied. The coating thickness and the carbon content in the coatings were found to be the critical parameters for the barrier property. The novel barrier coating was applied on different polymeric materials, and it increased the barrier property of the modified low‐density polyethylene, polyethylene terephthalate, and polylactide by 96.48%, 99.69%, and 99.25%, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Permeation of oxygen and water vapor through EVOH films as influenced by relative humidity

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 (O₂TR) as functions of RH and temperature were developed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1866–1872, 2001     

Studies on effect of nanoclay on the properties of thermally sprayable EVA and EVAI coatings

Dispersion of nanoclay (NC) in polymer blend system is governed by the sequence of addition of different ingredients. In the present work nanoclay was added in different sequences to blend composition such as ethylene vinyl acetate (EVA)/low density polyethylene (LDPE) and ethylene vinyl alcohol (EVAl)/LDPE in internal mixer to get nanocomposite. It was found that sequential addition of individual polymers and nanoclay influenced mechanical properties of resulting composites. Blending sequence of PE/NC/EVA and PE/NC/EVAl gave best mechanical properties. After optimization of addition sequence, concentration of nanoclay was varied from 1 to 8% by weight in the polymer blend. The resulting composites were evaluated in terms of their mechanical properties, dispersion characteristics (XRD), water vapor transmission rate (WVTR) and water absorption (Wa). Nanocomposite containing EVA/LDPE blend with 4% nanoclay showed optimum properties. The optimized composition was applied on grit blasted mild steel specimens by flame spray technique. The coated specimens were evaluated for adhesion strength, abrasion resistance and resistance to corrosion properties.     

Impact of the coating process on the molecular structure of starch‐based barrier coatings

Molecular analysis of starch structure can be used to explain and predict changes in physical properties, such as water vapor and oxygen barrier properties in packaging materials. Solution casting is a widely used technique to create films from starch formulations. This study compared the molecular properties of these standard films with those of experimental coatings applied to paper in laboratory‐scale and pilot‐scale trials, with all three techniques using the same starch formulation. The results revealed large differences in molecular structure, i.e., cross‐linking and hydrolysis, between films and coatings. The main differences were due to the shorter drying time allowed to laboratory‐scale coatings and the accelerated drying process in pilot trials owing to the high energy output of infrared dryers. Furthermore, surface morphology was highly affected by the coating technique used, with a rougher surface and many pinholes occurring in pilot‐scale coatings, giving lower water vapor permeability than laboratory‐scale coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41190.     

Novel clay‐based nanobiocomposites of biopolyesters with synergistic barrier to UV light,gas, and vapour

This article presents novel solvent cast biocomposites of poly(lactic acid) (PLA), polyhydroxybutyrate‐co‐valerate (PHBV), and polycaprolactone (PCL) with enhanced barrier properties to UV light, oxygen, water, and limonene by means of incorporating an organomodified mica‐based clay grade. The TEM results suggested a good clay dispersion but with no exfoliation in the three biopolyesters. In agreement with the crystallinity data, which was found to generally increase with increasing filler content, oxygen but specially water and d ‐limonene permeability coefficients were seen to decrease to a significant extent in the biocomposites and an optimum property balance was found for 5 wt % of clay loading in the three biopolymers. With increasing clay content, the light transmission of these biodegradable biocomposites decreased by up to 90% in the UV wavelength region due to the specific UV blocking nature of the clay used. As a result, these new biocomposites can have significant potential to develop packaging films, coatings and membranes with enhanced gas and vapor barrier properties and UV blocking performance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and barrier properties of polyvinyl chloride plasticized with dioctyl phthalate,epoxidized soybean oil,and epoxidized cardanol

Plasticized polyvinyl chloride (PVC) films were prepared by melt compounding and compression molding using epoxidized cardanol (EC), a biobased plasticizer and its plasticization effect was compared with epoxidized soybean oil (ESBO) and dioctyl phthalate (DOP). The mechanical, migration, thermal, and barrier properties of the plasticized films were compared. The effect of replacing DOP with EC on the properties of PVC films was also investigated. The tensile strength, elongation at break, tensile modulus and impact strength values of PVC/EC films were higher in comparison to PVC/DOP and PVC/ESBO films at a fixed plasticizer loading of 40 wt.%. Also, the films prepared with a mixture of DOP + EC showed higher tensile strength and elongation at break compared to that of films prepared with only DOP. The PVC/EC films showed good thermal stability and reduced oxygen transmission rate (OTR) compared to PVC/DOP films. The addition of graphene and nanoclay in the PVC/plasticizer system exhibited an increase in oxygen transmission. However, the oxygen barrier property of nano filler incorporated PVC/EC films was better than PVC/DOP films. All the films showed negligible water vapor transmission rate (WVTR).     

Nanoparticle effects on the morphology and mechanical properties of polypropylene spunbond webs

We report morphology and mechanical properties of natural nanoclay incorporated spunbond polypropylene composite webs. Nanocomposite spunbond webs were produced with up to 5 wt % natural nanoclay additives on Reicofil®‐2 spunbond line. Influence of nanoclay on the resin rheological properties, processibility, and mechanical properties of webs were studied. Wide angle X‐ray diffraction and transmission electron microscopy analysis were used to investigate the nanocomposite morphology. Intercalated and flocculated morphology was observed for all the concentrates and for all the spunbond fiber webs. The microstructure and polymer morphology in the presence of additives was characterized using a polarized optical microscope. At higher percentage, excess clay platelets were excluded out of the spherulite boundaries. About 20–30% increase in tear strength was observed for webs with up to 2 wt % nanoclay additives. Compared with the control polypropylene spunbond web, nanoclay reinforced samples showed better dimensional stability. Different failure mode was observed for spunbond webs with additives. Spunbond webs with even as low as 1 wt % clay retain their morphology and integrity in bond point after thermal bonding. Nanoclay incorporated spunbond webs showed significant improvements in the stiffness. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chitosan‐coated paper: Effects of nisin and different acids on the antimicrobial activity

Chitosan coatings prominently improved both the gloss and oxygen barrier properties of paper. The gloss value in the machine direction was increased as a function of added chitosan. An oxygen‐permeability value of 1.1 cm³/m² d was obtained when 6.9 g/m² chitosan was applied to 80 g/m² copy paper. In addition, the effects on the mechanical properties were positive, but not significant. The water‐vapor permeability of the paper increased as a result of the chitosan coating. Chitosan dissolved in 1.6, 3.2, and 6.4% lactic acid showed antimicrobial activity against Bacillus subtilis, whereas acetic and propionic acids (1.6, 3.2, and 6.4%) did not produce any notable activity. Nisin (0.08 g/L) did not enhance the antimicrobial activity of coatings prepared from chitosan dissolved in different acids. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 986–993, 2004     

Morphology,order, light transmittance,and water vapor permeability of aluminum‐coated polypropylene zeolite composite films

In this study, the polypropylene–zeolite composite films having 2–6 wt % natural zeolite were coated with a thin film of aluminum (Al) by magnetron sputtering, and the contribution of the Al coating on film properties was investigated. The samples were characterized by EDX, X‐ray diffraction, SEM, AFM, UV–visible spectroscopy, and water vapor permeation analyses. The surface of the films coated with a smooth Al film having 98–131 nm thickness. EDX revealed that Al percentage on the surface appeared to be as 8–10 wt % indicating contribution of polymer surface under Al film to analysis. XRD analysis showed that the grain size of Al at the surface was 22–29 nm. The surface roughness increased after Al‐coating process. The transmission of coated films was very low for both UV and visible regions of the light spectrum. Permeation analysis indicated that water vapor permeation was lower for Al‐coated material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Active packaging material based on buriti oil – Mauritia flexuosa L.f. (Arecaceae) incorporated into chitosan films

Active and biodegradable materials have great potential in food packaging applications, improving the safety and quality of products. The objective of this study was to develop a new material based on buriti oil incorporated into a chitosan film. Different concentrations of buriti oil in dried films (2.1 g/m², 10.4 g/m², 20.8 g/m², and 31.3 g/m²) were added into a chitosan matrix (41.7 g/m²). The chitosan/buriti oil films were characterized by water‐vapor barrier properties, total water‐soluble matter (TSM), tensile properties, thermogravimetric analysis, microstructure, microbial permeation properties, and biodegradation estimation. The higher oil concentration improved the water‐vapor barrier and the buriti oil acted largely as a plasticizer and increased the elongation at break, and decreased the tensile strength (TS) of chitosan films. The total water‐soluble matter of chitosan films decreased in function of the buriti oil concentration, but the biodegradation and thermal stability increased. The chitosan films presented a microbial barrier against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43210.