Composite films from spruce galactoglucomannans with microfibrillated spruce wood cellulose

Two future wood biorefinery products, spruce galactoglucomannans (GGM) and microfibrillated spruce wood cellulose (MFC), were mixed to form composite films. The films were plasticized with different amounts of glycerol, and the preparation of films was successful even with low glycerol contents. The film properties were studied using optical microscopy and scanning electron microscopy, x-ray diffraction, water sorption, dielectric analysis, moisture scanning dynamic mechanical analysis, and tensile testing. The addition of MFC clearly affected the properties of the films by decreasing the moisture uptake and increasing the relative humidity of softening of the films and by increasing the glass transition temperature, tensile strength, and Young’s modulus of the films. The effect of MFC addition on the tensile properties of films was emphasized at low glycerol contents. The addition of MFC did not affect the degree of crystallinity of GGM in the films, which was between 20 and 25%. MFC can be efficiently used as reinforcement of GGM films to form wood-based composite materials and to prepare GGM-based films and coatings with low plasticizer content.     

Regenerated cellulose film with enhanced tensile strength prepared with ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc)

In this study, environmentally friendly regenerated cellulose films with enhanced tensile strength were successfully prepared by incorporation of plasticizer agents using 1-ethyl-3-methylimidazolium acetate as solvent. The results of morphology from scanning electron microscopy and atomic force microscopy showed that cellulose films possessed homogeneously, and exhibited smooth structure. ¹³C CP/MAS NMR spectra showed that the regenerated cellulose films were transferred from cellulose I to cellulose II. Moreover, the incorporation of plasticizer agents, especially in the presence of glycerol, significantly improved the tensile strength of cellulose film (143 MPa) as compared to the controlled sample. The notable properties of the regenerated cellulose films are promising for applications in transparent packaging.     

Blend films of natural wool and cellulose prepared from an ionic liquid

Natural wool/cellulose blends were prepared in an ionic liquid green solvent, 1-butyl-3-methylimidazolium chloride (BMIMCl) and the films were formed subsequently from the coagulated solutions. The wool/cellulose blend films show significant improvement in thermal stability compared to the coagulated wool and cellulose. Moreover, the blend films exhibited an increasing trend of tensile strength with increase in cellulose content in the blends which could be used for the development of wool-based materials with improved mechanical properties, and the elongations of the blends were considerably improved with respect to the coagulated films of wool and cellulose. It was found that there was hydrogen bonding interaction between hydroxyl groups of wool and cellulose in the coagulated wool/cellulose blends as determined by Fourier transform infrared (FTIR) spectroscopy. The ionic liquid was completely recycled with high yield and purity after the blend film was prepared. This work presents a green processing route for development of novel renewable blended materials from natural resource with improved properties.     

Mechanical,thermal and barrier properties of pectin/cellulose nanocrystal nanocomposite films and their effect on the storability of strawberries (Fragaria ananassa)

In this work, two formulations of pectin/cellulose nanocrystals/glycerol nanocomposites were employed as packaging to extend storage life of strawberries. The effects of incorporating cellulose nanocrystals extracted from bleached Kraft wood pulp on the mechanical, thermal, and barrier properties of pectin‐based nanocomposites were evaluated. Nanocomposite films with different filler levels of cellulose nanocrystals (1, 2, 4 and 8% w/w) were prepared by casting. Compared with the neat film of pectin, improvements in the mechanical properties of the nanocomposites were observed, but these films became fragile. To improve the film flexibility, glycerol was added as a plasticizer and then new variations in the mechanical, thermal, and barrier properties of these nanocomposites were evaluated. The effects of nanocomposite films on storability of strawberries were compared with Poly vinyl chloride packaging films. The Poly vinyl chloride film and the nanocomposites showed similar behavior regarding weight loss by the strawberries, especially in the initial days of storage. The results show that pectin/cellulose nanocrystals/glycerol nanocomposites could be considered as a viable packaging alternative for replaced the Poly vinyl cloride film. Copyright © 2015 John Wiley & Sons, Ltd.     

Properties of cellulose films prepared from NaOH/urea/zincate aqueous solution at low temperature

Cellulose films were successfully prepared from NaOH/urea/zincate aqueous solution pre-cooled to −13 °C by coagulating with 5% H₂SO₄. The cellulose solution and regenerated cellulose films were characterized with dynamic rheology, ultraviolet–visible spectroscope, scanning electron microscopy, wide angle X-ray diffraction, Fourier transform infrared (FT-IR) spectrometer, thermogravimetry and tensile testing. The results indicated that at higher temperature (above 65 °C) or lower temperature (below −10 °C) or for longer storage time, gels could form in the cellulose dope. However, the cellulose solution remained a liquid state for a long time at 0–10 °C. Moreover, there was an irreversible gelation in the cellulose solution system. The films with cellulose II exhibited better optical transmittance, high thermal stability and tensile strength than that prepared by NaOH/urea aqueous solution without zincate. Therefore, the addition of zincate in the NaOH/urea aqueous system could enhance the cellulose solubility and improve the structure and properties of the regenerated cellulose films.     

Microfibrillated cellulose (MFC): pullulan bionanocomposite films

The aim of this work was to develop and characterize microfibrillated cellulose (MFC)/pullulan bionanocomposites. Fourier transform infrared spectroscopy suggested that the affinity between the two polymers resulted in new hydrogen bonding of the nanocomposite materials compared to pristine pullulan. At the same time, an increase in crystallinity was observed proportional to the amount of MFC used, as shown by the X-ray analyses. Accordingly, final films showed improved mechanical properties proportionally to the filler loading, with impressive elastic modulus and tensile strength of ~4.50 GPa and ~60 MPa, respectively, for the sample containing 10 % MFC. However, as demonstrated by the moisture sorption isotherms, the addition of MFC did not help reduce the amount of water adsorbed by the samples. In addition, the oxygen and water vapor permeability data clearly showed that final films still suffered high relative humidity values, whereas their barrier performance toward oxygen was excellent under dry conditions, with O₂ permeability coefficients (P′O ₂) comparable with those of common high barrier films/coatings. Finally, while the nanocomposites in the form of films had high haze values (from 23 to 40 %), the same nanocomposites in the form of coatings were decidedly more transparent, which suggests that their use as thin layers could be more suitable when the “see-through” capability must be preserved, for example in food packaging applications.     

Sisal cellulose and its acetates: generation of films and reinforcement in a one-pot process

This study was undertaken to evaluate both the properties of cellulose acetate films as a function of their degree of substitution (DS) and the possibility of generating reinforcements during film preparation. Sisal was selected for the entire study, among other reasons, because it is a rapidly growing source of cellulose. Cellulose acetates with various DS values were prepared in a homogeneous medium (dimethylacetamide/lithium chloride as the solvent system) and characterized. In DMAc/LiCl, cellulose and cellulose acetate films (mixed or not mixed with sisal cellulose) were successfully prepared and characterized. The films with high DS values exhibited lower hygroscopicity, a distinct morphology (scanning electron microscopy images), and lower tensile strength. In some cases, the films prepared from acetates/cellulose exhibited higher tensile strength and/or storage modulus than the acetate films. This result suggested a reinforcing action of the auto-organized cellulose chains that enabled the generation of both a film and reinforcement in a one-pot process.     

The role of nanocellulose fibers, starch and chitosan on multipolysaccharide based films

Thin nanocomposite films of thermoplastic starch, chitosan and cellulose nanofibers (bacterial cellulose or nanofibrillated cellulose) were prepared for the first time by solvent casting of water based suspensions of the three polysaccharides. The role of the different bioploymers on the final properties (thermal stability, transparency, mechanical performance and antimicrobial activity) of the films was related with their intrinsic features, contents and synergic effects resulting from the establishment of interactions between them. Thermoplastic starch displays an important role on the thermal stability of the films because it is the most stable polysaccharide; however it has a negative impact on the mechanical performance and transparency of the films. The addition of chitosan improves considerably the transparency (up to 50 % transmittance for 50 % of chitosan, in respect to the amount of starch), mechanical performance and antimicrobial properties (at least 25 % of chitosan and no more than 10 % of cellulose nanofibers are required to observe bacteriostatic or bactericidal activity) but decrease their thermal stability. The incorporation of cellulose nanofibers had the strongest positive impact on the mechanical properties of the materials (increments of up to 15 and 30 MPa on the Young′s modulus and Tensile strength, respectively, for films with 20 % of BC or NFC). Nonetheless, the impact in thermal stability and mechanical performance of the films, promoted by the addition of chitosan and cellulose nanofibres, respectively, was higher than the expected considering their percentage contents certainly because of the establishment of strong and complex interactions between the three polysaccharides.     

纤维素/明胶复合膜的超分子结构与性能

通过一种绿色的方法在NaOH/尿素水体系中制备出纤维素和明胶组成的复合膜(C/G),并且证明这两种大分子间存在强的氢键作用,导致明胶耐水性明显改善.同时,用戊二醛作为交联剂对复合膜化学交联,进一步提高其抗水性.通过红外光谱(FTIR)、紫外光谱(UV-Vis)、13C固体核磁共振谱、扫描电镜(SEM),力学和溶胀测试对...     

Wheat gluten films obtained by compression molding

Edible films based on plasticized wheat gluten protein were prepared by intensive mixing followed by compression molding. The effects of water and glycerol, which were selected as plasticizers for the wheat gluten, as well as the processing conditions (mixing time and molding temperature) on the physical and mechanical properties of the films were evaluated. The resulting films were characterized in terms of moisture sorption, total soluble matter, water vapor permeability, dynamic mechanical and tensile properties. It was found that plasticizer type and concentration had a dominating effect on mechanical properties and WVP, while other physical properties remain almost non-affected. Moreover, the effect of the added plasticizer (glycerol) on the film properties strongly depends on natural presence of water in commercial gluten (9% as is). On the other hand, the pressing temperature affected the final properties of the films more than the mixing time because the former influences the final cross-linking degree of the protein network. Processing temperatures higher than 100 °C led to darker films that would be discarded by consumers if they were used as food packaging.     

Mechanical properties of films made from dialcohol cellulose prepared by homogeneous periodate oxidation

2,3-Dialdehyde celluloses were prepared by homogeneous periodate oxidation in an aqueous solution of methylol cellulose. Since methylol cellulose stays dissolved in water for a certain time before decomposing gradually into regenerated cellulose, the oxidation reaction progressed homogeneously throughout the period. The resulting dialdehyde cellulose achieved an oxidation level of over 90 % in as little as 12 h. Reducing the dialdehyde celluloses with NaBH₄ resulted in water-soluble dialcohol celluloses, which have an open-ring structure at the C2–C3 position. The dialcohol celluloses were characterized using nuclear magnetic resonance spectrometry, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The T_g of the products decreased with increasing oxidation levels. The products might be processable, and unique tensile properties were obtained by cutting the C2–C3 bonds in the glucopyranose rings. The dialcohol celluloses prepared using a cast method yielded clear and transparent films which showed unique mechanical properties by tensile tests depending on the values of oxidation level.     

Nanocomposite films based on cellulose reinforced with nano-SiO2: microstructure, hydrophilicity, thermal stability, and mechanical properties

Microcrystalline cellulose/nano-SiO₂ composite films have been successfully prepared from solutions in ionic liquid 1-allyl-3-methylimidazolium chloride by a facile and economic method. The microstructure and properties were investigated by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, water contact angle, thermal gravimetric analyses, and tensile testing. The results revealed that the well-dispersed nanoparticles exhibit strong interfacial interactions with cellulose matrix. The thermal stability and tensile strength of the cellulose nanocomposite films were significantly improved over those of pure regenerated cellulose film. Furthermore, the cellulose nanocomposite films exhibited better hydrophobicity and a lower degree of swelling than pure cellulose. This method is believed to have potential application in the field of fabricating cellulose-based nanocomposite film with high performance, thus enlarging the scope of commercial application of cellulose-based materials.     

Anomalous reinforcing effects in cellulose gel-based polymeric nanocomposites

Cellulose-synthetic polymer nanocomposite films were prepared by immersion of cellulose gel in polymer solutions followed by dry casting. The cellulose hydrogel was prepared from aqueous alkali-urea solution. As the synthetic polymer, polystyrene (PS) and poly(methyl methacrylate) (PMMA) were used. The polymer content could be changed between 10 and 80% by changing polymer concentration of immersing solution. While the mechanical properties of the cellulose-PMMA composite films showed a nearly linear dependence on PMMA content, those of cellulose-PS composites showed an anomalous behavior; both tensile strength and Young’s modulus showed prominent maxima at 15–30 wt% PS contents. This anomaly may have resulted from the specific interaction between the aromatic ring of PS and the hydrophobic plane of the glucopyranoside. Both PMMA and PS composite films showed significant improvements in dimensional thermal stability; up to 25 wt% synthetic polymer content, the coefficient of thermal expansion (CTE) was as low as ca. 30 ppm/K, about 1/3 of the pure polymers. This indicates that the regenerated cellulose network is effective in suppressing thermal expansion of the synthetic polymers.     

Preparation of gelatin/poly(vinyl alcohol) film modified by methyl methacrylate and gamma irradiation

The properties of gelatin–polyvinyl alcohol (G–PVA) blend films were improved by methyl methacrylate (MMA) and γ irradiation for a practical viewpoint. The films were prepared by the casting method, modified by glycerol and MMA monomer, and their mechanical properties were also studied. The gelatin-based films were successfully prepared using γ irradiation (3.1 kGy) and gelatin: PVA = 97:3 (w/w) as optimized. Tensile properties of the films were studied and thermal properties of the films were characterized by thermogravimetric analysis and dynamic mechanical analysis pointed out that MMA treated both gelatin films, and G–PVA blend films showed less thermal degradation than untreated films. In addition, structural and morphological features of the gelatin-based films were examined by Fourier transform infrared and scanning electron microscopy, respectively. The ultimate results of the present study showed remarkable enhancement in tensile properties (> 40%) and a reduction in elongation at break of the films, thanks to the MMA addition and γ irradiation.     

Biobased films prepared from NaOH/thiourea aqueous solution of chitosan and linter cellulose

In the present study, films based on linter cellulose and chitosan were prepared using an aqueous solution of sodium hydroxide (NaOH)/thiourea as the solvent system. The dissolution process of cellulose and chitosan in NaOH/thiourea aqueous solution was followed by the partial chain depolymerization of both biopolymers, which facilitates their solubilization. Biobased films with different chitosan/cellulose ratios were then elaborated by a casting method and subsequent solvent evaporation. They were characterized by X-ray analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis, and tests related to tensile strength and biodegradation properties. The SEM images of the biofilms with 50/50 and 60/40 ratio of chitosan/cellulose showed surfaces more wrinkled than the others. The AFM images indicated that higher the content of chitosan in the biobased composite film, higher is the average roughness value. It was inferred through thermal analysis that the thermal stability was affected by the presence of chitosan in the films; the initial temperature of decomposition was shifted to lower levels in the presence of chitosan. Results from the tests for tensile strength indicated that the blending of cellulose and chitosan improved the mechanical properties of the films and that an increase in chitosan content led to production of films with higher tensile strength and percentage of elongation. The degradation study in a simulated soil showed that the higher the crystallinity, the lower is the biodegradation rate.     

Effect of sunlight on the preparation and properties of cellulose/silver nanoparticle composite films by in situ method using Ocimum sanctum leaf extract as a reducing agent

Cellulose/silver nanoparticle composite films with in situ-generated silver nanoparticles (AgNPs) were prepared using Ocimum sanctum leaf extract as a reducing agent in the absence and presence of sunlight and were characterized by SEM, FTIR, XRD, and antibacterial tests. Sunlight hastened up the preparation of these composite films. The average size of the in situ-generated AgNPs was reduced by the sunlight. The antibacterial activity and other properties of the composites were enhanced by the sunlight. The cellulose/AgNP composite films with improved properties by sunlight can be considered for medical purpose as antibacterial dressing materials.     

Development of Nanocomposites from Bacterial Cellulose and Poly(vinyl Alcohol) using Casting-drying Method

Nanocomposites of bacterial cellulose (BC) and poly(vinyl alcohol) (PVA) were prepared by cast-drying method as an easy way in producing nanocomposite films and to expand the use of BC. The contribution of PVA in nanocomposites was evaluated by measurement of cross-sectional surface, moisture uptake and mechanical properties. Morphological analysis shows that PVA covered a number of cellulosic fibres and formed denser material as a function of PVA addition. Based on the tensile test, the addition of PVA causes a very slight reduction compared with bacterial cellulose itself. The BC/PVA nanocomposites still have similar stiffness to BC with elongation at break less than 5%, while PVA film shows ductile properties with elongation at break more than 80%. On the other hand, the presence of BC fibres in the PVA matrix enhanced the tensile strength and the elastic modulus of pure PVA about two to three times, but it decreased the toughness of pure PVA. The highest tensile strength and elastic modulus of the nanocomposites are 164 MPa and 7.4 GPa, respectively at BC concentration of 64%. Increasing BC concentration is proportional to reducing moisture uptake of BC/PVA nanocomposites indicating that the existence of BC fibres inhibits moisture absorption.     

Influence of urea and glycerol on functional properties of biodegradable PVA/xylan composite films

In recent years, numerous studies have focused on biodegradable plastics for agricultural applications. To improve the mechanical and hydrophobic properties, biodegradable xylan composite films containing poly(vinyl alcohol) (PVA) were successfully prepared by casting method in this work. A series of composite films at a PVA/xylan weight ratio of 3:1 under the addition of glycerol and urea were investigated. Influences of the urea and glycerol amounts on the functional properties of composite films such as hydrophilicity/hydrophobicity, water vapor permeability (WVP), mechanical properties, solubility and degradability were comparatively investigated. Results showed that increasing the glycerol amount led to a decrease in tensile strength and an increase in elongation at break and WVP, while the addition of 1 % urea in composite films without glycerol had a positive impact on improving the water resistance of composite films; the contact angle and WVP values reached 114.68° and 4.11 × 10^?11 g m^?1 s^?1 Pa^?1. Moreover, thermogravimetric analysis, FTIR and a scanning electron microscope were used to confirm the compatibility of the PVA and xylan components. FTIR analysis displayed the intensity of hydroxyl groups of films became stronger with increasing amounts of glycerol, while the opposite results were obtained with an increase of the amount of urea. These indicated that glycerol could improve the miscibility between PVA and xylan, and the addition of urea could enhance the water resistance of composite films.     

细菌纤维素膜的制备与性能

以细菌纤维素为原料,氯化锂(LiCl)/二甲基乙酰胺(DMAc)为溶剂,通过相转化法制备了细菌纤维素膜.用单纤维强力仪对膜的拉伸强度和伸长率进行测试,分析了细菌纤维素浓度、凝固浴温度、凝固浴浓度、凝固时间及塑化条件对膜力学性能的影响.结果表明:在一定范围内,随着制膜液中细菌纤维素浓度的增加、凝固浴温度的降低和凝固浴浓度的增大,膜的拉伸强度和伸长率均提高;随着甘油浓度的增大和塑化时间的延长,膜的拉伸强度逐渐减小,伸长率逐渐增大.     

Formulation and characterization of in situ generated copper nanoparticles reinforced cellulose composite films for potential antimicrobial applications

Cellulose was dissolved in aq.(LiOH + urea) solution pre-cooled to –12.5°C and the wet films were prepared using ethyl alcohol coagulation bath. The gel cellulose films were dipped in 10 wt.% Cassia alata leaf extract solution and allowed the extract to diffuse into them. The leaf extract infused wet cellulose films were dipped in different concentrated aq. copper sulphate solutions and allowed for in situ generation of copper nanoparticles (CuNPs) inside the matrix. The morphological, structural, antibacterial, thermal, and tensile properties of dried cellulose/CuNP composite films were carried out. The presence of CuNPs was established by EDX spectra and X-ray diffraction. The composite films displayed higher thermal stability than the matrix due to the presence of CuNPs. Cellulose/CuNP composite films possessed better tensile strength than the matrix. The composite films showed good antibacterial activity against E.coli bacteria. We conclude that good antibacterial activity and better tensile properties of the cellulose/CuNP composite films make them suitable for antibacterial wrapping and medical purposes.