Bio‐hybrid nanocomposite coatings from sonicated chitosan and nanoclay

Nanocomposite films and coatings with improved properties were produced from ultrasonic dispersed chitosan and hydrophilic bentonite nanoclay. Bio‐hybrid coatings were applied onto argon–plasma‐activated LDPE coated paper. The intercalation of chitosan in the silicate layers was confirmed by the decrease of diffraction angles as the chitosan/nanoclay ratio increased. Nanocomposite films and multilayer coatings had improved barrier properties against oxygen, water vapor, grease, and UV‐light transmission. Oxygen transmission was significantly reduced under all humidity conditions. In dry conditions, over 99% reduction and at 80% relative humidity almost 75% reduction in oxygen transmission rates was obtained. Hydrophilic chitosan was lacking the capability of preventing water vapor transmission, thus total barrier effect of nanoclay containing films was not more than 15% as compared with pure chitosan. Because to very thin coatings (≤1 μm), nanoclay containing chitosan did not have antimicrobial activity against test strains. All coating raw materials were “generally recognized as safe” (GRAS) and the calculated total migration was in all cases ≤6 mg/dm², thus the coatings met the requirements set by the packaging legislation. Processing of the developed bio‐hybrid nanocomposite coated materials was safe as the amounts of released particles under rubbing conditions were comparable with the particle concentrations in a normal office environment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Biobased mineral‐oil barrier‐coated food‐packaging films

Toxic mineral oils can migrate into foods from cardboard boxes made of recycled fibers. This is an emerging issue for the whole dry‐food‐packaging industry. Breakfast cereals, for example, are typically packaged in boxes with or without inner bags and consumed without further processing. Currently, fossil‐based high‐density polyethylene (HDPE) films are used as a major raw material for such inner bags. However, HDPE is a very poor barrier against mineral‐oil migration. Biobased coatings from cellulose nanofibrils (CNFs), hydroxypropylated xylan, and hydroxypropylated cellulose were applied onto biobased high‐density polyethylene (bio‐HDPE) films, and the mineral‐oil barrier properties were evaluated. All of the coated films significantly decreased the migration of n‐decane, isobutylbenzene, 1‐cyclohexylbutane, 1‐cyclohexylheptane, and 1‐cyclohexyldecane. Biobased barrier bags prepared from (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxy oxidized CNF coated bio‐HDPE film protected the content to a great extent from mineral‐oil migration compared to noncoated bio‐HDPE and other commercial breakfast cereal‐bag films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44586.     

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     

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.     

Preparation and evaluation of chitosan‐coated polyphosphazene hydrogel beads for drug controlled release

Chitosan‐coated polyphosphazene‐Ca²⁺ hydrogel beads were fabricated by dropping polyphosphazene into CaCl₂/chitosan gelling solution. Polyphosphazene used here was a water‐soluble degradable polyanion (PCPAP), which carried almost two carboxylatophenamino groups on each phosphorus atom of the polymer backbone. Two kinds of turbidimetric titration were applied in this study to reveal the interaction between PCPAP and chitosan within the pH range of 4.57≈7.14. The effect of gelling solution pH on the properties of chitosan‐coated PCPAP beads was especially emphasized. It was found that the PCPAP/chitosan complex prepared at relatively high pH (pH 6.5) dissociated most slowly in pH 7.4 phosphate‐buffered solution (PBS). The erosion of chitosan‐coated beads and the release of model drug (Coomassie brilliant blue and myoglobin) in PBS were both obviously prolonged with the increase of gelling solution pH, exhibiting perfect accordance with the behavior of complex dissociation. In addition, the coating of PCPAP/chitosan complex on the bead surface facilitated the improvement of drug loading efficiency. The higher the gelling solution pH, the more the drug loading efficiency improved. At pH 6.5 (PCPAP 5%, CaCl₂ 7%, chitosan 0.3%), the loading efficiency of myoglobin in beads reached as high as 93.2%. These results indicate that the chitosan‐coated polyphosphazene‐ Ca²⁺ bead is a potential formulation for drug controlled release. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1993–1999, 2004     

Aqueous Solution‐Processable,Flexible Thin‐Film Transistors Based on Crosslinked Chitosan Dielectric Thin Films

The hydrophilic character of chitosan (CS) limits its use as a gate dielectric material in thin‐film transistors (TFTs) based on aqueous solution‐processable semiconductor materials. In this study, this drawback is overcome through controlled crosslinking of CS and report, for the first time, its application to aqueous solution‐processable TFTs. In comparison to natural CS thin films, crosslinked chitosan (Cr‐CS) thin films are hydrophobic. The dielectric properties of Cr‐CS thin films are explored through fabrication of metal–insulator–metal devices on a flexible substrate. Compared to natural CS, the Cr‐CS dielectric thin films show enhanced environmental and water stabilities, with a high breakdown voltage (10 V) and low leakage current (0.02 nA). The compatibility of Cr‐CS dielectric thin films with aqueous solution‐processable semiconductors is demonstrated by growing ZnO nanorods via a hydrothermal method to fabricate flexible TFT devices. The ZnO nanorod‐based TFTs show a high field‐effect mobility (linear regime) of 10.48 cm² V^?1 s^?1. Low temperature processing conditions (below 100 °C) and water as the solvent are utilized to ensure the process is environmental friendly to address the e‐waste problem.     

Preparation and properties of poly(urethane acrylate) (PUA) and tetrapod ZnO whisker (TZnO‐W) composite films

Tetrapod zinc oxide whiskers (TZnO‐Ws) were successfully synthesized via a thermal oxidation method and confirmed using Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy. A series of poly(urethane acrylate) (PUA)/TZnO‐W composite films with various TZnO‐W contents were prepared via a UV curing method and their physical properties were investigated to understand their possible use as packaging materials. The morphological, thermal, mechanical, antibacterial and barrier properties of the PUA/TZnO‐W composite films were interpreted as a function of TZnO‐W content. The thermal stability, barrier properties and antibacterial properties of the composite films, which were strongly dependent upon their chemical and morphological structure, were enhanced as the TZnO‐W content increased. The oxygen transmission rate and water vapor transmission rate decreased from 614 to 161 cm³ m^?2 per day and 28.70 to 28.16 g m^?2 per day, respectively. However, the mechanical strength of the films decreased due to the low interfacial interaction and poor dispersion with high TZnO‐W loading. The enhanced barrier properties and good antibacterial properties of the PUA/TZnO‐W composite films indicate that these materials are potentially suitable for many packaging applications. However, further studies are needed to increase the compatibility of polymer matrix and filler. © 2012 Society of Chemical Industry     

Preparation and characterization of soy protein isolate–carboxymethylated konjac glucomannan blend films

To improve the mechanical and water vapor barrier properties of soy protein films, the transparent films were prepared by blending 5 wt % soy protein isolate (SPI) alkaline water solution with 2 wt % carboxymethylated konjac glucomannan (CMKGM) aqueous solution and drying at 30 °C. The structure and properties of the blend films were studied by infrared spectroscopy, wide‐angle X‐ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and measurements of mechanical properties and water vapor transmission. The results demonstrated a strong interaction and good miscibility between SPI and CMKGM due to intermolecular hydrogen bonding. The thermostability and mechanical and water vapor barrier properties of blend films were greatly enhanced due to the strong intermolecular hydrogen bonding between SPI and CMKGM. The tensile strength and breaking elongation of blend films increased with the increase of CMKGM content: the maximum values achieved were 54.6 MPa and 37%, respectively, when the CMKGM content was 70 wt %. The water vapor transmission of blend films decreased with the increase of CMKGM content: the lowest value achieved was 74.8 mg · cm^?2 · d^?1 when the CMKGM content was 70 wt %. The SPI–CMKGM blend films provide promising applications to fresh food packaging. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1095–1099, 2003     

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     

Preparation and characterization of antimicrobial PVA hybrid films with N‐halamine modified chitosan nanospheres

Chitosan is a promising candidate as an antimicrobial agent in food packaging materials and biomaterials due to its biocompatibility, biodegradability, non‐toxicity and biocidal activity. In this study, chitosan derivatives, α‐(5,5‐dimethyl hydantoin amino)‐chitosan (CS‐HDH), were synthesized. The CS‐HDH nanospheres were prepared by ionic gelation method and characterized by SEM, FT‐IR, XRD, and TGA‐DTG. The prepared novel chitosan nanospheres in the range of 200–300 nm had good dispersibility. The CS‐HDH nanospheres were used to prepare antibacterial PVA hybrid films by solvent evaporation technique. The surface morphology and thermal property of hybrid films were measured by SEM, AFM, and TGA‐DTG. The results of antibacterial test showed that the hybrid film with 1.24 × 10¹⁸ atoms/cm² of active chlorine exhibited excellent antibacterial properties against Staphylococcus aureus and Escherichia coli O157:H7, and all of bacteria could be inactivated within 5 min. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44204.     

Composite membranes of chitosan and titania‐coated carbon nanotubes as promising materials for new proton‐exchange membranes

Titania‐coated carbon nanotubes (TCNTs) were obtained by a simple sol–gel method. Then chitosan/TCNT (CS/TCNT) composite membranes were prepared by stirring chitosan/acetic acid and a TCNT/ethanol suspension. The morphology, thermal and oxidative stabilities, water uptake and proton conductivity, and mechanical properties of CS/TCNT composite membranes were investigated. The CNTs coated with an insulated and hydrophilic titania layer eliminated the risk of electronic short‐circuiting. Moreover, the titania layer enhanced the interaction between TCNTs and chitosan to ensure the homogenous dispersion of TCNTs in the chitosan matrix. The water uptake of CS/TCNT composite membranes was reduced owing to the decrease of the effective number of the ? NH₂ functional groups of chitosan. However, the CS/TCNT composite membranes exhibited better performance than a pure CS membrane in thermal and oxidative stability, proton conductivity, and mechanical properties. These results suggest that CS/TCNT composite membranes are promising materials for new proton‐exchange membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43365.     

Improving the physical and chemical functionality of starch‐derived films with biopolymers

The physical and chemical properties of composite starch‐based films containing cellulosic fiber, chitosan, and gelatin were investigated. Films containing both cellulosic fibers and chitosan demonstrated tremendous enhancements in film strength and gas permeation. The water absorbency of composite films could be greatly reduced in film composites containing cellulosic fibers and gelatin, but the inclusion of chitosan into these films provided a higher hydrophilicity, increasing water absorbency. Film transparency was not noticeably affected in the composite films that were made. These films may have wide application in the food packaging, agricultural mulching, and the medical industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2542–2548, 2006     

Bone cell attachment and growth on well‐characterized chitosan films

Chitosan has been widely researched for bone tissue and implant applications. While initial results are promising, there are inconsistent reports regarding the biological responses. This may be due to inadequate evaluation of chitosan material properties. This study evaluated normal human osteoblast precursor cell attachment and proliferation on a series of well‐characterized chitosan films. The chitosan films exhibited a range of properties: 76–96% degree of de‐acetylation (DDA), 2400–8200 kDa viscosity‐average molecular weight, 62–90° contact angle, 0.24–2.46% residual ash, 5.3–287 µg cm^?2 residual protein and 23–40% crystallinity. There was no trend or correlation between DDA, crystallinity, contact angle, molecular weight, residual ash or protein content and the attachment or growth of bone cells on chitosan films. All films supported higher levels of bone cell proliferation than tissue culture plastic, which supports the general hypothesis that chitosans are osteocompatible. The 78 and 92% DDA chitosan films supported the most cell proliferation, approximately 16 times that of tissue culture plastic controls, but no chitosan physiochemical property correlated with the increased cell growth. The lack of correlation is hindered since more than one physiochemical property changed for each chitosan material. Data do indicate that there may be much variability in chitosan materials, and this variability may make understanding and comparing biological performance of chitosan materials difficult. These results highlight the need for systematic characterizations of chitosan materials for predictable biomedical applications. Copyright © 2006 Society of Chemical Industry     

Structure and properties of regenerated cellulose films coated with polyurethane–nitrolignin graft‐IPNs coating

A regenerated cellulose film (RC) was coated with a graft‐IPNs coating, which was composed of castor oil‐based polyurethane and 2.8 wt % nitrolignin (NL), to obtain water‐resistant films. The effects of NCO/OH molar ratio and different polyols, such as 1,4‐butanediol (BDO) and trimethanol propane (TMP), on the structure and properties of the coated RC films were investigated. With an increase of the NCO/OH molar ratio, the tensile strength of the coated films increased, but the water resistivity and size contraction hardly changed. The coated films with TMP exhibited the higher breaking elongation at 1.5 of the NCO/OH molar ratio, while those with BDO have more excellent tensile strength, water resistivity, and dimensional stability. The coated films with the graft‐IPNs coating exhibited superior water resistivity and dimensional stability. The light transmittance of the coated films was more excellent than that of the RC film. Moreover, the results from the IR and electron probe microanalysis (EPMA) showed that the chemical bonding occurred between cellulose and coating, and the introduction of NL plays an important role in the enhancement of the interface adhesion of the coated films. Atomic force microscopy (AFM) depicted the flat and dense surface of the coated films, which restricted the water vapor penetration and the size contraction, resulting in the enhancement of water resistivity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1799–1806, 2002     

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     

Barrier properties of paper–chitosan and paper–chitosan–carnauba wax films

A gas barrier and biodegradable multilayer material was processed with a paper substrate, chitosan, and carnauba wax. The first step consisted of the study of the chitosan coating to obtain a dense polymer layer at the paper surface. The influence of the molecular weight and the concentration of the chitosan solution were studied, and a chitosan coating of 7 g/m² was achieved, which led to interesting gas barrier properties in the anhydrous state. Nevertheless, the hydrophilic character of both cellulose and chitosan did not allow us to preserve these properties in the hydrated state. A layer of carnauba wax was then deposited on the chitosan face of the bilayer. Because of the hydrophobic character of this external layer, the water sorption in the multilayer decreased greatly, and CO₂ and O₂ permeability coefficients lower than 0.5 barrer were obtained in the hydrated state. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 704–710, 2005     

Properties and interfacial bonding of regenerated cellulose films coated with polyurethane–chitosan IPN coating

Water-resistant films were prepared by coating a castor oil-based polyurethane–chitosan (PU–CH), in which grafted interpenetrating polymer networks (IPNs) were produced, on a regenerated cellulose (RC) film. The tensile strengths of the coated films cured at 90°C for 5 min reached 853 kg cm⁻² (dry state) and 503 kg cm⁻² (wet state) and were obviously higher than those of the films of uncoated and coated with PU coating. Moreover, the coated films have excellent water resistivity, low vapor permeability, and good size stability, and their optical transmittance is even better than that of the RC film in the range of 400–800 nm. The interfacial structure of the coated films was investigated by using spectroscopy infrared, ultraviolet spectroscopy, transmission electron microscopy, and electron probe microanalysis. It was shown that the strong interfacial bonding with chemical and hydrogen bonds between the RC film and the coating exists. The PU prepolymer in the IPN coating penetrated through the interface into the RC film and partly crosslinked with the cellulose, forming a semi-IPNs. The chitosan in the PU–CH coating plays an important role not only in accelerating the cure of the coating but also in improving the mechanical properties and biodegradability of the coated film. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1313–1319, 1998     

Mechanical behavior at nanoscale of chitosan‐coated PE surface

Chitosan coating of polyethylene (PE) was proposed as a new procedure to improve its biocompatibility and surface properties. The functionalization of the PE film surface by covalent bonding of chitosan coating and its effect on the surface mechanical properties, as surface elasticity, stiffness, and adhesion (that are important in different biological processes) were investigated by nano‐indentation, scratch, and atomic force microscopy. It has been established that chitosan grafting onto corona functionalized PE surface using various coupling agents significantly improves the surface hardness and elastic modulus although they decrease in depth of the layer. Compared to the neat PE substrate, the chitosan coated samples show significant improved friction properties and tear resistance. The surface roughness features correlate with the micro‐mechanical parameters. Therefore, the covalent immobilization of the chitosan onto PE leads to a stable coating with better mechanical performance being recommended as a promising material for medical applications and food packaging. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42344.     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry