High oxygen barrier materials from paper to regenerated cellulose films

A transparent, bendable, high oxygen barrier cellulose-based film was prepared, which has far better oxygen barrier properties than conventional polyethylene, polypropylene and cellophane materials. A series of regenerated cellulose films (RCs) were prepared from filter paper lacking oxygen barrier properties under different cellulose concentrations and gelation times. It was shown that the cellulose concentration and gel time had a greater effect on the oxygen barrier properties of RCs. When the cellulose concentration was 4 wt% and the gel time was 3 h, the RCs obtained the lowest oxygen permeability coefficient (OPC) down to 2.21 × 10⁻¹⁷ cm³ cm cm⁻² s⁻¹ Pa⁻¹. The films have a tensile strength of 109.5 MPa, an elongation at break of 27.3% and a light transmission rate of 89%. In further, molecular dynamics simulations showed that when the filter paper was converted to RCs, the increase in hydrogen bonding and the decrease in free volume between cellulose chains caused a decrease in the diffusion coefficient of oxygen. As a novel biobased high oxygen barrier material, the film has broad application prospect in packaging and chemical industry.     

Preparation and characterization of transparent cellulose films using an improved cellulose dissolution process

Effective dissolution of cellulosic macromolecules is the first predominant step to prepare functional bio‐based materials with desirable properties. In this study, we developed an improved dissolution process using a freeze‐drying pretreatment to promote the dissolution of cellulose. Rheological measurements of cellulose solutions and physicochemical characterization of regenerated cellulose films (scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis) were performed. Cellulose solution prepared from 5% microcrystalline cellulose (w:v) in the solvent exhibits a Newtonian fluid character while cellulose solutions at higher concentrations show a pseudo‐plastic fluid behavior. Results from physicochemical characterization indicate that a freeze‐drying pretreatment step of cellulose leads to a complete dissolution at 5% concentration while only part of cellulose is dissolved at 10% and 15% concentrations. The results obtained indicated that the use of a freeze‐drying pretreatment step under mild conditions lead to a complete dissolution of cellulose at 5% concentration. The cellulose films prepared from 5% concentration exhibited desirable properties such as good optical transparency, crystallinity, and thermal stability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44871.     

Regenerated cellulose aerogel: Morphology control and the application as the template for functional cellulose nanoparticles

This article focuses on controlling the morphology of regenerated cellulose aerogel (RCA) and its application as a template for the preparation of functional cellulose nanoparticles (FCNPs). RCA is prepared by lyophilizing cellulose hydrogel which is fabricated through a sol–gel method in sodium hydroxide (NaOH)/urea aqueous solution. The morphology of RCA is adjusted by varying the gelation temperature and time. With the gelation temperature and time increasing, lamellar RCA transforms into strings of cellulose nanoparticles. Subsequently, RCA with the morphology of "strings of nanoparticles" is modified through the bulk condensation of l -lactic acid and RCA. Eventually, the prepared functionalized RCA (FRCA) is dispersed in an organic solvent to obtain purified FCNPs. The results demonstrate that single FCNP can be obtained by dispersing FRCA in dimethyl sulfoxide. Moreover, the prepared FCNPs have uniform size, good thermal-stability, and increasing hydrophobicity, which are ideal candidates for polymer composites in terms of fillers.     

The fabrication of flexible and oxygen barrier cellulose nanofiber/polylactic acid nanocomposites using cosolvent system

The main disadvantages of polylactic acid (PLA) for food packaging applications are its brittleness and poor gas barrier properties. The purpose of this study is to evaluate the potential usability of triethyl citrate (TEC) and cellulose nanofiber (CNF) in PLA to obtain bio-based films with optimal properties. The incorporation of CNF as reinforcement fillers in polymer matrix has long been debated due to its difficulties to disperse uniformly in hydrophobic polymer matrix attribute to their hydrophobic nature. In order to overcome this problem, different feeding method for CNF into the mixer was studied, and CNF/PLA nanocomposites were characterized. It was found that CNF was successfully dispersed in the PLA matrix through the TEC-CNF suspension, which greatly improved tensile strength and flexibility of the CNF/PLA nanocomposites. The oxygen barrier property was enhanced up to 47.3% (16.99 cc·mm/m²·day·atm) with the increase loading of 0.25, 0.50, and 1 wt% of CNF. Moreover, the dynamic mechanical analysis showed that the low tan delta peak of CNF/PLA nanocomposites (48.25°C) was shifted to high peak (52.99°C) due to incorporation of TEC; indicates an improved of thermal stability of the composites. Overall, the t-CNF/PLA nanocomposites show a great feasibility for various eco-friendly flexible packaging applications.     

Nanocomposites of ethylene vinyl alcohol copolymer with thermally resistant cellulose nanowhiskers by melt compounding (II): Water barrier and mechanical properties

In the present work, the crystallinity and crystalline morphology, thermal stability, water barrier, and mechanical properties of ethylene vinyl alcohol copolymer (EVOH) nanocomposites prepared by melt compounding and incorporating both plant (CNW) and bacterial cellulose nanowhiskers (BCNW) are reported. An improvement in the water barrier performance was observed, that is, 67% permeability drop, only for the microcomposite sample incorporating 2 wt % of bacterial cellulose fibrils. No significant differences in the water‐barrier properties of the nanocomposites generated through the two studied preincorporation methods were observed despite the fact that an excellent dispersion was observed in the previous study. On the other hand, direct melt‐mixing of the freeze‐dried nanofiller with EVOH resulted in increased water permeation. The aggregation of the filler in the latter nanocomposite was also ascribed to the detrimental effect on the mechanical properties. Interestingly, by using the precipitation method, an increase in the elastic modulus and tensile strength of ～36 and 22%, respectively, was observed for a 3 wt % BCNW loading, which was thought to coincide with the percolation threshold. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyhydroxyalkanoate coatings restrict moisture uptake and associated loss of barrier properties of thermoplastic starch films

This work investigates the use of polyhydroxyalkanoate (PHA) films as moisture barriers for thermoplastic starch (TPS) films, to produce biodegradable, multi‐layer materials with high gas barrier properties. This is a necessary extension to the limited work available on this topic and confirms that PHAs are suitable coating materials for TPS films intended for use in food packaging. Under storage conditions of up to 75% relative humidity (RH) for 2 weeks, a PHA coating maintained the moisture content (MC) of the TPS below the point at which its barrier properties were detrimentally affected. Furthermore, for PHBV coating thicknesses of 91–115 μm, the MC of the TPS remains significantly lower than uncoated TPS for the duration of the experiment (>25 days). The flux of water into the coated TPS fit to a model based on Fick's law. However, when the multi‐layered films were stored at 95% RH delamination occurred within 24 h. Preliminary investigation into possible material design improvements showed that the addition of a small amount of PHA to the TPS layer prolonged the time to delamination. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46379.     

Comparison of bacterial cellulose production by Gluconacetobacter xylinus on bagasse acid and enzymatic hydrolysates

To fulfill the comprehensive utilization of cellulose and hemicellulose components in bagasse for bacterial cellulose (BC) production, both bagasse acid and enzymatic hydrolysates were used for BC production by Gluconacetobacter xylinus. Although the BC accumulation rate was slower during the early period of fermentation in the bagasse acid hydrolysate than in the enzymatic hydrolysate, the highest BC yield (1.09 vs. 0.42 g/L) was higher in the bagasse acid hydrolysate. The substrate utilization was evaluated in both bagasse acid and enzymatic hydrolysates, and glucose, xylose, and acetic acid were better carbon sources than arabinose and cellobiose for G. xylinus. The structure of the BC samples obtained from bagasse acid and enzymatic hydrolysates, including the microscopic morphology, functional groups, and crystals, was similar especially in the later phase of fermentation, which was analyzed by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. Thus, both bagasse acid and enzymatic hydrolysates could be promising substrates for BC production. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45066.     

Morphology,mechanical, and physical properties of wet-spun cellulose acetate fiber in different solvent-coagulant systems and in-situ crosslinked environment

Wet spinning is a popular fiber manufacturing process where the effects of solvent and coagulant on the wet-spun fiber are significant. In this study, we have explored the effect of solvent-coagulant interaction and in-situ crosslinking on the wet-spun cellulose acetate (CA) fiber. Investigation on 12 different solvent-coagulant systems revealed that variation in the systems resulted in significant variance in morphology and mechanical property of the fiber. Remarkable increase in mechanical property was observed after in-situ crosslinking with citric acid and polyethylene glycol (PEG). Inclusion of sodium hypophosphite (NaH₂PO₂) as catalyst further increased tensile modulus (~407%) and crystallinity index (~46%) compared to CA fiber crosslinked with only citric acid. It was established that fiber from CA-DMSO solution crosslinked with 10% citric acid and 10% PEG extruded in ethanol showed the highest tensile modulus (~30 MPa). This in-depth study found an appropriate combination of solvent-coagulant for forming stable CA fiber, with the addition of crosslinkers and catalyst further increasing the strength and usability of the fiber.     

Starch nanocomposite films incorporating grape pomace extract and cellulose nanocrystal

The objectives of this study were to prepare starch nanocomposite films incorporating grape pomace extract (GPE) and cellulose nanocrystal (CNC) using a solvent‐casting method, and to characterize the mechanical properties, color, water vapor transmission rate (WVTR), crystalline structure, morphology, thermal stability, phenolic compound release profile and antibacterial activity of the films. Incorporating CNC and GPE significantly (P < 0.05) increased the films’ thickness, mechanical properties, and opacity. Brightness and color were mainly influenced by GPE level, while CNC had a great impact on the reduction of WVTR values of the film. Three characteristic cellulose I crystalline peaks were observed using X‐ray diffraction in CNC‐containing nanocomposite films. However, the effect of CNC levels on thermal stability was not significant. Phenolic compound releases were time and film dependent, and the nanocomposite films incorporating with GPE and CNC exhibited stronger inhibitory effect against Staphylococcus aureus ATCC 29213 compared to Listeria monocytogenes ATCC 7644. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44438.     

Mechanical recycling of nanocellulose containing multilayer packaging films

The aim of this study was to demonstrate mechanical recycling of low density polyethylene (LDPE) films coated with a thin layer of cellulose nanofibrils (CNFs). CNF acts as an effective barrier against oxygen and mineral oil residues. Two different CNF grades were tested, and both were applied onto plasma activated LDPE film using a pilot coating line. The coated films were shredded with the help of liquid nitrogen, compacted and compounded with virgin LDPE and compatibilizer, and processed into cast films and injection molded test specimens. The CNF coatings were completely blent as microscale agglomerates in the LDPE matrix. The effect of these agglomerates on the barrier and heat sealing properties was statistically insignificant compared to recycled uncoated LDPE. The mechanical properties were only moderately changed. CNF‐coated LDPE films can therefore be recycled back into films without sacrificing the characteristic properties of the base polymer. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46237.     

Water-repellent films from corn protein and tomato cutin

Flexible and hydrophobic biobased films were obtained using zein esterified with methanol and para-toluene (p-toluene) sulfonic acid, cutin from tomato peels and ethanol. Esterification was confirmed by proton nuclear magnetic resonance and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR). Non-modified zein films were brittle and hydrophilic. ATR-FTIR demonstrated that zein esterification increased zein hydrophobicity. Without cutin, esterified zein films were hydrophobic but brittle. Addition of cutin yielded films that were flexible and hydrophobic, as demonstrated by contact angle measurements. Principal component analysis (PCA) of ATR-FTIR data showed that intensities at 3195 cm⁻¹ and 3490 cm⁻¹ were correlated to the relative hydrophobicity of zein films. PCA also showed that films of esterified zein and cutin were more hydrophobic than their counterparts (non-modified zein without cutin). Optical and scanning electron microscopy demonstrated that esterified zein was compatible with cutin and yielded cohesive films, which did not fracture upon bending.     

Mushroom polysaccharides‐incorporated cellulose nanofiber films with improved mechanical,moisture barrier,and antioxidant properties

Mushroom polysaccharides (MP), including white MP, brown MP, and enoki MP, were incorporated into cellulose nanofiber (CNF). Studies on thermal property, structure, crystallinity, and morphology of CNF‐MP films revealed that MP was well interacted with and adsorbed onto CNF. Incorporation of MP significantly (P < 0.05) increased tensile strength and reduced water vapor permeability of CNF film. CNF‐MP films possessed higher antioxidant activity than CNF only or CNF‐chitosan film, and the antioxidant activity of released components from CNF‐MP films immersed in water was higher than that released from films immersed in methanol. Radical scavenging activity and reducing ability were major antioxidant mechanisms of CNF‐MP films. These trends were consistent with the results of total phenolics content released from films and the antioxidant activity of MP themselves. This study demonstrated CNF‐MP films may be used as packaging material for preventing oxidation and/or dehydration of food during storage. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46166.     

Production of recycled cellulose fibers from waste paper via ultrasonic wave processing

Recycling waste paper can be considered as a means to displace the use of natural cellulose fibers applied in building materials, because it is composed mostly of cellulose. The water absorption and special surface area of cellulose fibers are the key properties for their use in building materials. The objective of this article was to study the production of recycled cellulose fibers from waste paper using ultrasonic wave processing. The physical and chemical properties of recycled cellulose fibers, such as water absorption, specific surface area and pore characteristics, etc., were investigated with various testing methods. The results indicated that the ultrasonic cavitation effect was feasible for the preparation of the secondary fibers. When the ultrasonic treatment time lasted for 10 min, the water absorptions of both newsprint fibers and kraft fibers increased significantly and reached the highest values of 12.5 g/g and 11.2 g/g, respectively, which were nearly two times than that of fibers without ultrasonic treatment. With a pretreatment of 20 min, the average length and fineness of recycled cellulose fibers decreased by 4% and 25%, respectively, and the length‐diameter ratio of the recycled cellulose fibers was 1.28 times than that of the untreated fibers, which greatly increased the special surface area of the recycled cellulose fibers. This work also determined that NaOH was useful to improve the physical properties of the recycled cellulose fibers. Because the recycled cellulose fibers after processing, fulfilled several technical indexes, they can be considered as a filling material for used in cement‐based materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41962.     

Cassava starch‐based nanocomposites reinforced with cellulose nanofibers extracted from sisal

Cellulose nanofibers were extracted from sisal and incorporated at different concentrations (0–5%) into cassava starch to produce nanocomposites. Films' morphology, thickness, transparency, swelling degree in water, water vapor permeability (WVP) as well as thermal and mechanical properties were studied. Cellulose nanofiber addition affected neither thickness (56.637 ± 2.939 µm) nor transparency (2.97 ± 1.07 mm^?1). WVP was reduced until a cellulose nanofiber content of 3.44%. Tensile force was increased up to a nanocellulose concentration of 3.25%. Elongation was decreased linearly upon cellulose nanofiber addition. Among all films, the greatest Young's modulus was 2.2 GPa. Cellulose nanofibers were found to reduce the onset temperature of thermal degradation, although melting temperature and enthalpy were higher for the nanocomposites. Because cellulose nanofibers were able to improve key properties of the films, the results obtained here can pave the route for the development and large‐scale production of novel biodegradable packaging materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44637.     

Encapsulation of cinnamaldehyde into nanostructured chitosan films

Recently, bioactive chitosan films featuring naturally derived essential oils have attracted much attention due to their intrinsic antimicrobial properties and applicability to a broad range of applications. Previously, the ability to form thick (t > 100 µm), chitosan‐essential oil films via solution casting has been demonstrated. However, the fabrication of well characterized ultrathin films (t < 200 nm) that contain essential oils remain unreported. Here, we systematically investigate increasing the incorporation of an essential oil, cinnamaldehyde (CIN) into ultrathin chitosan films. Films with and without the surfactant Span^®80 were spin‐coated. Qualitatively, films exhibited well‐defined structural color, which quantitatively ranged from 145 to 345 nm thick. Release studies confirmed that a 6× higher release of CIN was enabled by Span^®80 versus the chitosan control films, 30 µg versus 5 µg, respectively. These results suggest that nanostructured chitosan‐CIN coatings hold potential to delay bacterial colonization on a range of surfaces, from indwelling medical device to food processing surfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41739.     

Effect of five saturated fatty acids on the properties of sweet‐potato‐starch‐based films

To fully explore the influences of saturated fatty acids (SFAs) on the properties of sweet‐potato‐starch (SPS)‐based films, five SFAs were chosen to add to SPS. The SPS‐based films were prepared by casting. The microstructure, mechanical, optical, water vapor barrier, and thermal properties of the films were investigated. The 2.0% (w/w, on the basis of starch) SFA significantly changed the SPS pasting characteristics in the peak viscosity, breakdown, and other feature point viscosity values as determined by a Rapid Visco Analyser. The amylose molecular weights decreased as measured by high‐performance size exclusion chromatography. A thermal study with differential scanning calorimetry suggested that the addition of SFA increased the onset temperature and peak temperature. Scanning electronic microscope (SEM) images showed a continuous and uniform structure in the films with SFA. The SPS–SFA composite films showed lower light transmission and elongation at break than the control. Compared with the control films, the addition of SFA increased the tensile strength and decreased the water vapor permeability of the films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41380.     

Polylactide films produced with bixin and acetyl tributyl citrate: Functional properties for active packaging

Packaging materials are decisive to preserve the quality and nutritional value of food. Polylactide (PLA) is a biodegradable polymer with adequate mechanical properties for packaging applications, but its moderate oxygen barrier properties and high UV light transmission hamper its performance as packaging for oxygen- and light-sensitive products. Bixin, a carotenoid with coloring and antioxidant character, was used to improve the light barrier of PLA films plasticized or not with acetyl tri-butyl citrate (ATBC). The films were subjected to thermal treatment mimicking polymer processing temperatures. Despite more than 74 wt% of bixin degraded during heat treatment, films were still blocking up to 95% of UVA and 90% of UVB transmission. Plasticizing PLA with ATBC accelerated up to six times the bixin release into a food simulant, which allowed to reach relevant concentrations for food preservation. In conclusion, bixin is a promising natural antioxidant and UV-shielding additive of biodegradable packaging.     

Understanding external plasticization of melt extruded PHBV–wheat straw fibers biodegradable composites for food packaging

The objective of this work is to get further knowledge on the external plasticization mechanisms of melt extruded polyhydroxyl‐3‐butyrate‐co?3‐valerate (PHBV) when combined with wheat straw fibers (WSF). Different types of biodegradable substances, all authorized for food contact according to the European regulation, i.e., acetyltributyl citrate (ATBC), glycerol triacetate (GTA) and (PEG) at different molecular weights, were tested at different percentages (5, 10 and 20 wt %). Thermal and mechanical characterization of PHBV/plasticizer blends showed that a significant plasticizing effect was obtained using hydrophobic substances such as ATBC and GTA, with an increase of the elongation at break from 1.8% up to about 6% for an additive content of 10 wt %. However, the incorporation of WSF in plasticized PHBV led to a dramatic decrease in the elongation at break of composites, neutralizing the increase of this parameter by the addition of the plasticizers. The stress at break of plasticized films was also significantly decreased by the introduction of fibers. Such a loss of ductility was mainly explained by the occurrence of microscopic defects in the materials induced by the presence of fibers and to a poor adhesion at the fiber/matrix interface. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41611.     

Construction of porous cellulose tubes and the evaluations of mechanical properties and cytocompatibility

In this work, regenerated cellulose (RC) tubes with the porous structure were successfully fabricated for constructing the non-invasive detection platform of vascular microenvironment. Polyethylene oxide (PEO) as a porogen was applied to induce porous structure of cellulose tubes. Tensile and burst pressure tests were carried out to evaluate the effects of PEO molecular weight and amount on the mechanical properties of cellulose tubes. The results showed that tensile strength of RC tubes was increased with increasing PEO molecular weight. The compliance of cellulose tubes decreased with increasing the PEO content. When 120 kDa PEO was applied, the average tensile strength of RC tubes could reach 1.27 MPa. The maximum burst pressure and compliance of RC tubes could reach 488.25 ± 35 mmHg and 7.50 ± 3.7%/100 mmHg, respectively. Human umbilical vein endothelia cells (HUVECs) exhibited obvious proliferation on cellulose tubes, and the collagen coating further improve the biocompatibility. The incorporated collagen further improved adhesion of the cells and growth on cellulose tubes. This work provided a kind of cellulose-based tube material with potential application for the construction of the vitro vascular microenvironment.     

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.