Bio-nanocomposite films reinforced with cellulose nanocrystals: Rheology of film-forming solutions, transparency, water vapor barrier and tensile properties of films

Reinforcement of Refined and Semi-Refined Carrageenan Film with Nanocellulose

Carrageenans obtained from seaweeds can be processed into films for a range of applications including food packaging. The level of carrageenan refinement during extraction can influence the key properties, with semi-refined carrageenan (SRC) containing more impurities than the more refined carrageenan (RC). Further refinement steps, however, result in higher costs associated with the production of RC. In order to obtain a lower cost and more ecofriendly, bio-based material for food packaging applications, SRC was used in this investigation to produce a thin film reinforced with nanocellulose fibrils (NCF). Films derived from RC containing NCF were also investigated with water sensitivity and physico-mechanical and thermal properties among the properties tested. Levels of NCF were varied from 1% to 7% (w/w), and in general, the NCF reinforcement improved the overall properties of both the SRC and RC films, including the water sensitivity and moisture barrier. However, NCF inclusion in SRC film was less effective with regard to the mechanical and thermal properties compared with NCF inclusion in RC film. The enhancement in properties was attributed to the greater cohesiveness of the reinforced polymer structure and the crystalline regions formed in the structures of SRC and RC films by NCF incorporation.

Structure and properties of thermomechanically processed chitosan/carboxymethyl cellulose/graphene oxide polyelectrolyte complexed bionanocomposites

Bionanocomposites of chitosan and chitosan/carboxymethyl cellulose (CMC) polyelectrolyte complexed materials with graphene oxide (GO) or reduced graphene oxide (rGO) were prepared by thermomechanical processing with excellent levels of dispersion. While GO has a greater affinity with the chitosan polycation, rGO had a more pronounced effect on properties resulting in increased tensile strength, Shore D hardness, and thermal stability of both matrices. Although GO is more hydrophilic than rGO, the former increased more effectively the surface hydrophobicity of the biocomposites regardless of matrix type. GO and rGO changed the α-transition of the biocomposites in a similar manner. The electrochemical properties of the biocomposites were influenced by both nanofiller type and matrix. This research revealed that inclusion of 2D carbon nanomaterials can alter biopolymer interactions and that the phase structure of the biopolymer blend may play a more important role than nanofiller-matrix interactions in determining the overall properties of these bionanocomposites.

Comparison of cast films and hydrogels based on chitin nanofibers prepared using TEMPO/NaBr/NaClO and TEMPO/NaClO/NaClO2 systems

Neutral TEMPO/NaClO/NaClO₂ (TNN) oxidation, with NaClO₂ as the primary oxidant under aqueous conditions at pH 6.8 was applied to selectively oxidize surface C6 primary hydroxyl groups of α-chitin to carboxylate groups. When 0.1 mmol TEMPO, 1 mmol NaClO and 20 mmol NaClO₂ were added to 1 g α-chitin, the yield of water-insoluble oxidized chitin was 91.93 %, and the carboxylate content was 0.695 mmol/g. The TNN oxidized chitin (TNN-Ch) was mostly converted to individual nanofibrils by mechanical disintegration in water, with mostly widths of 20-24 nm and average lengths of 1 μm. Compared to chitin nanofibers produced by TEMPO/NaBr/NaClO system (TBN-ChNs), with average widths of 16.67 ± 7.9 nm and average lengths of 770 ± 170 nm, TNN-ChNs were wider, longer and had a higher aspect ratio; its films and hydrogels also showed better mechanical properties, which indicated the size effect on the nanofiber-based materials resulted from different oxidation process.

Carboxymethyl cellulose-based antioxidant and antimicrobial active packaging film incorporated with curcumin and zinc oxide

Carboxymethyl cellulose (CMC)-based functional films were prepared by incorporating curcumin (0.5 and 1.0 wt% based on CMC), ZnO (1 wt% based on CMC). The FE-SEM showed that the ZnO and curcumin were uniformly dispersed in the CMC film. The CMC/curcumin/ZnO composite films showed significantly increased UV-barrier without much sacrifice of transparency, and they also showed increased water vapor barrier properties. The mechanical properties of the composite film were slightly reduced by the addition of 1 wt% curcumin, while unchanged by the addition of 1 wt% ZnO, but improved by the combined addition of curcumin (0.5 wt%) and ZnO (1 wt%). CMC films incorporated with curcumin showed strong antioxidant activity, while films incorporated with ZnO showed strong antimicrobial activity against foodborne pathogenic bacteria. The CMC film with the addition of ZnO (1 wt%) and curcumin (1 wt%) (CMC/Cur^1.0/ZnO^1.0) was optimal for producing functional films with antioxidant and antibacterial properties.

Stable and Highly Ion-Selective Membrane Made from Cellulose Nanocrystals for Aqueous Redox Flow Batteries

The design of chemically stable ion-exchange membranes with high selectivity for applications in an aqueous redox flow battery (RFB) at high acid concentrations remains a significant challenge. Herein, this study designed a stable and highly ion-selective membrane by utilizing proton conductive cellulose nanocrystals (CNCs) incorporated in a semicrystalline hydrophobic poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix. The high hydrophobicity of the PVDF-HFP matrix mitigates crossover of the electrolytes, whereas the abundant and low-cost CNCs derived from wood provide high proton conductivity. The fundamental contributors for CNCs' excellent proton conductivity are the hydroxyl (-OH) functional groups, highly acidic sulfonate (-SO₃H) functional groups, and the extensive intramolecular hydrogen bonding network. In addition, CNCs exhibit a mechanically and chemically stable structure in the harsh acidic electrolyte attributed to the high crystallinity (crystalline index of ∼86%). Therefore, because of the high proton conductivity, excellent ion selectivity, high chemical stability, and structural robustness, the vanadium redox flow battery (VRFB) assembled with the homogeneous CNCs and PVDF-HFP (CNC/PVDF-HFP) membrane achieved a Coulombic efficiency (CE) of 98.2%, energy efficiency (EE) of 88.2%, and a stable cycling performance for more than 650 cycles at a current density of 100 mA cm^-2. The obtained membrane possesses excellent flexibility, high mechanical tensile strength, and superior selectivity. Meanwhile, the applied casting method is scalable for large-scale manufacturing.

Mechanical and Thermal Behavior of Canola Protein Isolate Films As Improved by Cellulose Nanocrystals

The effects of cellulose nanocrystals (CNCs) (12, 24, and 36% w/w) on the microstructure and mechanical and thermal properties of canola protein isolate films were evaluated. The incorporation of cellulose nanocrystals led to homogeneous films, and new Fourier transform infrared peaks appeared at 1055 cm^-1, indicating the presence and the interaction of CNCs with proteins and glycerol. The addition of CNCs also improved the thermal stability of the films, since higher temperatures were required for their thermal decomposition. In addition, CNC addition resulted in an increase in tensile strength and a decrease in elongation at break values due to strong interactions between the OH groups in proteins, glycerol, and CNCs.

Cross-linked starch-based edible coating reinforced by starch nanocrystals and its preservation effect on graded Huangguan pears

Starch-based nanocomposite film/coating made from cross-linked cassava starch reinforced by starch nanocrystals (SNCs) was successfully prepared. The effects of SNCs contents on the color, transparency, roughness, mechanical properties, water vapor permeability, and FTIR spectroscopy of the films were explored. The results showed that the film with 6% SNCs had the best comprehensive performance. Subsequently, graded Huangguan pears were coated with the formulation-optimized coating and stored at 20 °C for 4 weeks. From the physicochemical parameters of pears, it can be found that the grading treatment was detrimental to the preservation of pears, while the coating treatment was significantly effective for extending shelf life. Besides, the pattern of grading before coating was more advantageous for pear preservation. In general, this study firstly applied cross-linked starch-based nanocomposite coating on the preservation of pear, which had practical significance for expanding the use of nanocomposite coating reinforced by SNCs and pear preservation methods.

SPME-GC-MS & metal oxide E-Nose 18 sensors to validate the possible interactions between bio-active terpenes and egg yolk volatiles

This study was focused on the differences between three concentrations of four safe bio-active volatile terpenes and natural compounds (trans-cinnamaldehyde, thymol, menthol, and vanillin) on the egg yolk volatile components. In which, Headspace Solid phase Micro Extraction (HS-SPME) followed by GC/MS were used for volatiles analysis, and electronic nose (E-Nose) with 18 sensors was used for the aroma pattern. In the results, a total of 111 different volatile compounds were identified by using GC/MS. Some ketones, amines, nitro and organic acid compounds such as hexanone were significantly reduced after using these compounds. On the other hand, first principal components (PC1) of trans-cinnamaldehyde (0.1%) was decreased significantly (p < .05) to -4.8 ± 0.8, compared to the control with 4.3 ± 2.1. And, it increased benzaldehyde and nonanal peaks area significantly to 46.56 ± 14.46 and 9.22 ± 4.81 MPA. In menthol (0.1%), the content of d-limonene was decreased to 4.65 ± 0.49 MPA, compared to the control with 14.16 ± 4.95 MPA. On the other hand, by E-Nose, vanillin (0.1%) PC1 was decreased significantly to -4.48 ± 0.43. Moreover, thymol (0.1%) decreased hydrocarbon sensation to 0.448 ± 0.005. And, vanillin (0.1%) decreased hydrogen sulfide and ketones sensation to 0.169 ± 0.01 and 0.344 ± 0.01, respectively. In conclusion, this study is providing novel information to understand the effects of bio-active molecules on the biological fatty media volatility. Also, it explains how terpenes can protect egg yolk media from the unacceptable odor formation which results from the degradation of its lipids and proteins.

Effects of Hybridized Organically Modified Montmorillonite and Cellulose Nanocrystals on Rheological Properties and Thermal Stability of K-Carrageenan Bio-Nanocomposite

Herein, hybrid k-carrageenan bio-nanocomposite films were fabricated by using two types of nanofillers, organically modified montmorillonite (OMMT), and cellulose nanocrystals (CNCs). Hybrid bio-nanocomposite films were made by casting techniques employing 4 wt% of CNCs, OMMT, and hybridized CNCs/OMMT in a 1:1 ratio. The rheological and morphological properties and thermal stability of all composites were investigated using rotational rheometry, thermogravimetry analysis, differential scanning calorimetry, field emission scanning electron microscopy, and transmission electron microscopy (TEM). The results showed that the hybrid CNC/OMMT bio-nanocomposite exhibited significantly improved properties as compared to those for the bio-nanocomposites with single fillers due to the nanosize and homogenous nanofiller dispersion in the matrix. Rheological analysis of the hybrid bio-nanocomposite showed higher dynamic shear storage modulus and complex viscosity values when compared to those for the bio-nanocomposite with individual fillers. The TEM analysis of the hybridized CNC/OMMT bio-nanocomposite revealed that more particles were packed together in the CNC network, which restricted the matrix mobility. The heat resistance and thermal stability bio-nanocomposite k-carrageenan film enhanced rapidly with the addition of hybridized CNCs/OMMT to 275 °C. The hybridized CNCs/OMMT exhibited synergistic effects due to the good affinity through interfacial interactions, resulting in the improvement of the material properties.

Developing chitin nanocrystals for flexible packaging coatings

This study assessed the applicability of chitin nanocrystals employed in combination with an existing coating material intended for flexible packaging. The 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidized chitin nanocrystals (TOCNs) were applied 1) as an additive in a water-based acrylic resin (WBAR) that was then coated onto the surface of a biaxially oriented polypropylene (BOPP) film, and 2) as a neat layer in multilayered BOPP laminates bonded by a WBAR adhesive layer. The results indicated that the flow behavior and shear viscosity of the TOCN/WBAR system were dependent on TOCN contents. The TOCNs as a dispersed phase in the acrylic resin matrix did not improve the oxygen barrier property of the resulting coated BOPP. By contrast, the neat continuous TOCN coating layer improved the oxygen barrier property of the laminates of BOPP and TOCNs bonded by the acrylic resin, a 44% oxygen transmission rate reduction for a laminate with a 8.33-μm TOCN layer compared to the laminate without a TOCN layer. The inclusion of the TOCNs maintained the optical transparency of the resulting films.

Preparation, properties, and structural characterization of β-glucan/pullulan blend films

This study investigates the physico-mechanical and structural properties of β-glucan (BG)/pullulan (PUL) composite edible films successfully prepared with 0-0.3 g of BG. Results demonstrated that BG addition significantly increases the elongation at break (p < 0.05), tensile strength, and water dissolution time of the resulting films. The transparency of the 0.2PUL:0.1BG film and the oxygen barrier property of the 0.15PUL:0.15BG film decreased remarkably compared with those of the plain films (0.3PUL:0BG and 0PUL:0.3BG) and other composite films (p < 0.05). FTIR indicated hydrogen bonding interactions between PUL and BG molecules, and microstructural observations showed that aggregated BG is homogeneously dispersed in the PUL continuous matrix. Among the films tested, the thermal stability of the 0.15PUL:0.15BG film was the best. A PUL:BG mixing ratio of 0.15:0.15 is thus suggested to provide the best film properties. This research offers an alternative method to improve PUL-based edible films.

Reinforcement of Polylactic Acid for Fused Deposition Modeling Process with Nano Particles Treated Bamboo Powder

The focus of this report was to understand the tensile properties and dynamic mechanical properties of bamboo powder (BP) reinforced polylactic acid (PLA) composite filaments which were treated with nano calcium carbonate (CaCO₃), cellulose nanofibers (CNF), and micro-crystalline cellulose (MCC) using impregnation modification technology. The storage modulus (E’) of nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments increased compared with BP/PLA composite filaments before the glass transition temperature T_g. When the temperature was above T_g, the reinforcement effect of nano CaCO₃, MCC, and CNF gradually became less apparent. The loss modulus (E’’) and loss factor (tan δ_max) of the nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments was higher than that of BP/PLA composite filaments produced by the “one-step” method. The tensile strength (TS) results showed a similar trend. Compared with the control samples, the TS of nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the “one-step” method (and the “two-step” method) increased by 40.33% (and 10.10%), 32.35% (and −8.61%), and 12.32% (and −12.85%), respectively. The TS of nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the “one-step” method was slightly higher than those produced by the “two-step” method. The elongation at break (EAB) of BP/PLA composite filaments was higher than that of BP/PLA samples treated with nano CaCO₃, MCC, or CNF. The PLA and modified BP were readily accessible through a simple mixing process. The rheological investigation of such mixtures showed that nano CaCO₃, CNF, and MCC have different effects on the processability and rheological properties of composites.

The Effect of Nanofillers on the Functional Properties of Biopolymer-based Films: A Review

Waste from non-degradable plastics is becoming an increasingly serious problem. Therefore, more and more research focuses on the development of materials with biodegradable properties. Bio-polymers are excellent raw materials for the production of such materials. Bio-based biopolymer films reinforced with nanostructures have become an interesting area of research. Nanocomposite films are a group of materials that mainly consist of bio-based natural (e.g., chitosan, starch) and synthetic (e.g., poly(lactic acid)) polymers and nanofillers (clay, organic, inorganic, or carbon nanostructures), with different properties. The interaction between environmentally friendly biopolymers and nanofillers leads to the improved functionality of nanocomposite materials. Depending on the properties of nanofillers, new or improved properties of nanocomposites can be obtained such as: barrier properties, improved mechanical strength, antimicrobial, and antioxidant properties or thermal stability. This review compiles information about biopolymers used as the matrix for the films with nanofillers as the active agents. Particular emphasis has been placed on the influence of nanofillers on functional properties of biopolymer films and their possible use within the food industry and food packaging systems. The possible applications of those nanocomposite films within other industries (medicine, drug and chemical industry, tissue engineering) is also briefly summarized.

A review on versatile applications of blends and composites of CNC with natural and synthetic polymers with mathematical modeling

Cellulose is world's most abundant, renewable and recyclable polysaccharide on earth. Cellulose is composed of both amorphous and crystalline regions. Cellulose nanocrystals (CNCs) are extracted from crystalline region of cellulose. The most attractive feature of CNC is that it can be used as nanofiller to reinforce several synthetic and natural polymers. In this article, a comprehensive overview of modification of several natural and synthetic polymers using CNCs as reinforcer in respective polymer matrix is given. The immense activities of CNCs are successfully utilized to enhance the mechanical properties and to broaden the field of application of respective polymer. All the technical scientific issues have been discussed highlighting the recent advancement in biomedical and packaging field.

Preparation and characterization of homogeneous and enhanced casein protein-based composite films via incorporating cellulose microgel

Gelatin-coupled cellulose (GCC) microgel with whisker-like structure is prepared and used to incorporate into casein (CA) matrix to construct reinforced CA-based composite films by solution casting. The GCC microgel has excellent dispersibility and stability in water, which contributes to the hydrophobicity and significantly reduces the moisture absorption of the composite films, as well as a decrease in the water vapor permeability with an increase of GCC content at different relative humidity is also observed. Compared with pure casein material, the resultant CA-based composite films show more homogeneous and dense cross-sectional structure, and the cleavage temperature of the hydrogen bonds increases by 16 °C. In particular, their tensile strength and Young’s modulus increase by 6 and 3.5 times, respectively. These indicators are superior to that of the nanoparticle enhanced CA-based composite film. Moreover, the light transmittance of the CA-based films at 550 nm is about 88% when GCC content is higher than 9%. The above results could be attributed to the strong hydrogen bonds formed between GCC components and CA matrix, as further confirmed by fourier transform infrared spectra and X-ray diffraction analysis.

Influence of Nanocellulose Additive on the Film Properties of Native Rice Starch-based Edible Films for Food Packaging

BACKGROUND & OBJECTIVE

Starch-based edible films, which are transparent, odourless, biodegradable, tasteless, and semi-permeable to gases and food additives, have attracted the attention of the research community as the alternative food packaging materials to synthetic plastics. However, they pose poor water resistance and mechanical strength that should be improved for food packaging application. Few relevant patents to the topic have been reviewed and cited.

METHODS

Inclusion of nanoadditives in starch films can not only improve their mechanical and barrier properties but also can act as antimicrobial agent, oxygen scavenger, and biosensor. The present investigation is focussed on the effects of nanocellulose extracted from banana pseudostems on the film properties of rice starch-based edible films. Nanocellulose was extracted from dried banana pseudostems through isolation of cellulose and acid hydrolysis. Rice starch-based edible films were prepared through solution casting by adding nanocellulose of varying concentrations (0%, 2%, 4%, 6%, 8% & 10%).

RESULTS

The film properties, such as Water Vapour Permeability (WVP), mechanical strength (tensile strength, Young's modulus and percentage of elongation), film solubility in water and film colour, were determined. The test results were discussed and the effects of nanocellulose additives were studied.

CONCLUSION

From the results, it was clear that the addition of nanocellulose had improved the film properties, making the rice starch-based edible films a promising choice for food packaging applications.

Hybrid cellulose nanocrystal/alginate/gelatin scaffold with improved mechanical properties and guided wound healing

Nature derived biopolymers such as polysaccharides and collagen have attracted considerable attention in biomedical applications. Despite excellent biocompatibility and bioactivity, their poor mechanical properties could not meet the requirement for skin regeneration. In this study, cellulose nanocrystal (CNC) was incorporated into the calcium cross-linked sodium alginate/gelatin (SA/Ge) scaffold to reinforce its physicochemical properties. A novel sodium alginate/gelatin/cellulose nanocrystal (SA/Ge/CNC) scaffold was successfully prepared through electrostatic interaction of sodium alginate and gelatin, ionic cross-linking of calcium ions with sodium alginate, and incorporation of CNC. Afterwards, the SA/Ge and SA/Ge/CNC scaffolds were fully characterized and compared with scanning electron microscopy images, swelling behaviors, tensile strengths and contact angles. The involvement of CNC produces a hybrid SA/Ge/CNC scaffold with desired porous network, moderate swelling behavior, and superior mechanical strength (from 18 MPa to 45 MPa). Furthermore, in vitro cytotoxicity and cell growth assay using mouse embryonic fibroblast cells validated that SA/Ge/CNC scaffold was non-toxic and can prompt cell adhesion and proliferation. The in vivo skin regeneration experiments using the SA/Ge/CNC scaffold group showed an improved skin wound healing process with accelerated re-epithelialization, increased collagen deposition and faster extracellular matrix remodeling. Overall, the results suggested that the SA/Ge/CNC hybrid scaffold with enhanced mechanical performance and wound healing efficacy was a promising biomaterial for skin defect regeneration.

Cellulose nanocrystal (CNC) is incorporated into Ca²⁺ cross-linked alginate/gelatin (SA/Ge) scaffold to improve physical, chemical and biological aspects. The SA/Ge/CNC scaffold with enhanced wound healing efficacy is a promising biomaterial for skin defect regeneration.

Mechanical and moisture barrier properties of corn distarch phosphate film influenced by modified microcry stalline corn straw cellulose

BACKGROUND

In this paper, a novel modified microcrystalline corn straw cellulose (MMCSC) was prepared by ultrasonic/microwave-assisted treatment. Effective incorporation of MMCSC into corn distarch phosphate (CDP)-based composite films was investigated.

RESULTS

As the proportion of MMCSC was increased, tensile strength increased initially before decreasing, and the elongation at break always decreased. The composite film of MMCSC20 showed the lowest water vapor permeability (2.917 × 10^-7 g m^-1 h^-1 Pa^-1 ). The measurement of surface color showed that by the increasing of the MMCSC proportion in composite films, the L^* and b^* values and the total color difference (ΔE^* ) increased, while a^* values decreased. Fourier transform infrared spectroscopy and X-ray diffraction analysis indicated that, with the incorporation of MMCSC, the stable structure of the films was enhanced through cross-linking and the crystallinity was increased. A scanning electron microscopy study revealed the surface microstructure of films (MMCSC0-MMCSC30) was smooth and homogeneous, and there was no distinct separation in the matrix of composite films.

CONCLUSION

The incorporation of suitable MMCSC could improve the properties of composite films. The CDP-MMCSC films, which are completely biodegradable and environmental friendly, have a high potential to be used for food packaging. © 2018 Society of Chemical Industry.