Glucomannan composite films with cellulose nanowhiskers

Spruce galactoglucomannans (GGM) and konjac glucomannan (KGM) were mixed with cellulose nanowhiskers (CNW) to form composite films. Remarkable effects of CNW on the appearance of the films were detected when viewed with regular and polarizing optical microscopes and with a scanning electron microscope. Addition of CNW to KGM-based films induced the formation of fiberlike structures with lengths of several millimeters. In GGM-based films, rodlike structures with lengths of several tens of micrometers were formed. The degree of crystallinity of mannan in the plasticized KGM-based films increased slightly when CNW were added, from 25 to 30%. The tensile strength of the KGM-based films not containing glycerol increased with increasing CNW content from 57 to 74 MPa, but that of glycerol-plasticized KGM and GGM films was not affected. Interestingly, the notable differences in the film structure did not appear to be related to the thermal properties of the films.     

Arabinoxylan structure affects the reinforcement of films by microfibrillated cellulose

The chemical structure of rye arabinoxylan (rAX) was systematically modified, exploiting selective enzymes to mimic different naturally occurring xylans, i.e., its degree of substitution (DS) was decreased using α-l-arabinofuranosidase, and a controlled decrease in the degree of polymerization (DP) was performed using endo-1,4-β-d-xylanase. The arabinose to xylose ratio was decreased from 0.45 to 0.27 and the weight-average molar mass was decreased from 184,000 to 49,000 g/mol. The resulting samples were used to prepare films, as such, and with 15% (wt. − %) softwood-derived microfibrillated cellulose (MFC) to obtain novel plant-derived biocomposite materials. The enzymatic tailoring of rAX increased the crystallinity of films, evidenced by X-ray diffraction studies, and the addition of MFC to the debranched, low DS rAX induced the formation of ordered structures visible with polarizing optical microscopy. MFC decreased the moisture uptake of films and increased the relative humidity of softening of the films, detected with moisture scanning dynamic mechanical analysis. For the first time, the chemical structure of xylan was proven to significantly affect the reinforcement potential of nano-sized cellulose, as the tensile strength of films from high DP rAXs, but not that of low DP rAXs, clearly increased with the addition of MFC. At the same time, MFC only increased the Young’s modulus of films from rAX with high arabinose content, regardless of DP.     

Biodegradable poly(propylene carbonate)/layered double hydroxide composite films with enhanced gas barrier and mechanical properties

Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides(LDHs) were prepared by coprecipitation process in aqueous solution and further rehydrated to an organic modified LDH(OLDH) in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction(XRD) and scanning electron microscopy(SEM). A series of poly(propylene carbonate)(PPC)/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient(OP) and water vapor permeability coefficient(WVP) is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.     

Oxygen and oil barrier properties of microfibrillated cellulose films and coatings

The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene vinyl alcohol. At higher RH’s, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5–10 nm, although some larger aggregates were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure formed by the nanofibers resulted in superior oil barrier properties.     

Cationic wood cellulose films with high strength and bacterial anti-adhesive properties

In this work, periodate oxidized birch wood pulp and microfibrillated cellulose (MFC) were cationized using Girard’s reagent T or aminoguanidine. Cationic celluloses were used to obtain films via solvent-casting method, and the effects of the cationization route and the cellulose fiber source on the properties of the films were studied. Thermal and optical properties of the films were measured using differential scanning calorimetry and UV–Vis spectrometry, and the morphology of the films was examined using an optical microscope and a field emission scanning electron microscope. Bacterial anti-adhesive properties of the films were also studied using a modified leaf print method and against Staphylococcus aureus and Escherichia coli. Both cationizing agents exhibited similar reactivity with periodate oxidized celluloses, however, MFC had significantly higher reactivity compared to birch pulp. The films with high tensile strength (39.1–45.3 MPa) and modulus (3.5–7.3 GPa) were obtained from cationized birch pulp, aminoguanidine modification producing a film with slightly better mechanical properties. Modulus of the films was significantly increased (up to 14.0 GPa) when MFC was used as a cellulose fiber source. Compared to the unmodified MFC films, the cationic MFC films were less porous and significantly more transparent; however, they had slightly lower tensile strength values. It was found that aminoguanidine modified celluloses had no culturable bacteria on its surface and also exhibited resistance to microbial degradation, whereas there were culturable bacteria on the surface of Girard’s reagent modified films and they were partially degraded by the bacteria.     

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.     

Properties of poly(vinyl chloride)/wood flour/montmorillonite composites: Effects of coupling agents and layered silicate

Organomodified montmorillonite (OMMT) was prepared using cetylalkyl trimethyl amine bromide. OMMT and wood flour (WF) were surface-modified by silane coupling agent. They were melt-blended with polyvinyl chloride (PVC) and extruded into wood-plastic composite samples using one conical twin screw extruder. The effects of their contents on the composite mechanical properties were investigated. X-ray diffraction, transmission electron microscopy and scanning electron microscopy observed intercalation and dispersion of the OMMT. FTIR and X-ray photoelectron spectroscopy were used to analyze the silane-modification effects. The possible reaction mechanisms were proposed. After wood flour was modified by 1.5 phr silane, the impact strength and the tensile strength of wood flour-PVC composite were increased by 14.8% and 18.5%, respectively. Mechanical tests showed that the addition of OMMT did not enhance the untreated wood flour-PVC composites. However, adding 0.5% OMMT did improve the mechanical properties of the treated ones. The grafting improved the interfacial compatibility between components producing higher properties of the composites. Further addition of OMMT reinforced the composites. Too higher contents of silane and OMMT impaired some properties because of weak interfacial layer and higher concentrated stress. Cone calorimetry showed that the fire flame retardancy and smoke suppression of composites were strongly improved with the addition of OMMT.     

Breakthrough in the preparation of irradiated sodium alginate/polyethylene oxide blend films using methacrylate monomer

The present work is an attempt to prepare biodegradable films of sodium alginate (SA)/polyethylene oxide (PEO) blend tailored by methacrylate (MA) and γ irradiation following casting method. The effects of SA/PEO composition, glycerol as a plasticizer, methacrylate as a monomer, and radiation dose were investigated and it was found that the mechanical properties of the films strongly depend on the film-forming parameters. The incorporation of glycerol in the blend is crucial as it creates a suitable environment for monomer addition and points out that tensile strength of the films decreased, while the elongation at break increased. Moreover, it was found that the tensile properties were improved by the application of γ radiation as well as monomer treatment. The mechanical properties of the blend films integrated with MA monomer were higher than that without monomer at the analogous conditions. The structural and morphological features of the films were examined by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively.     

Electrical properties and X-ray diffraction of wood and wood plastic composite (WPC)

Wood plastic composite (WPC) of kadom, simul, mango and debdaro were prepared with two monomers, methylmethacrylate (MMA) and butylmethacrylate (BMA) using high energy ionizing radiation. X-ray diffraction and scanning electron microscope (SEM) studies reveal that significant grafting occurred with wood fiber. Electric properties like resistivity and dielectric constant of both wood and WPC were measured under different moisture contents and relative humidities. The resistivities of wood decreased dramatically with increase of moisture content, but those of WPC decreased very slowly with moisture content. The dielectric constant of wood increased significantly with moisture content but no significant difference was observed in the case of WPC within the range of moisture contents studied. The dielectric constants of untreated wood also increased with their densities.     

Physical and mechanical properties of graphene oxide/polyethersulfone nanocomposites

The aim of this study was to investigate physical and mechanical properties of graphene oxide (GO)/polyethersulfone (PES) nanocomposite films. The films were produced by solution casting method. The mechanical properties of composite films were evaluated by tensile test. A significant enhancement in the mechanical properties of neat PES films was obtained incorporating a small amount of GO loading (0.05–1 wt.%). The highest tensile strength was observed at 1 wt.% of GO. Comparisons were made between experimental data and the Halpin–Tsai model predictions for the tensile strength and modulus of GO/PES composites. The effect of an orientation factor on model predictions was also acquired. The hydrophilicity of the nanocomposite was evaluated by assessing contact angle and enhanced wet ability of the films was obtained with increasing the amount of GO up to 1%. The morphology of the nanocomposites was investigated using scanning electron microscopy and transmission electron microscopy and the results revealed a good dispersion of GO in the PES matrix. The thermal behavior of the composite was also studied. Thermal stability of composites was increased by adding the GO. Copyright © 2013 John Wiley & Sons, Ltd.     

Mechanical and oxygen barrier properties of films prepared from fibrillated dispersions of TEMPO-oxidized Norway spruce and Eucalyptus pulps

TEMPO-oxidized cellulose nanofibers (TOCN) were obtained from commercial Norway spruce and mixed Eucalyptus cellulose pulps using TEMPO/sodium bromide (NaBr)/sodium hypochlorite (NaClO) system at pH 10 and 22 °C. After reaction, the fibrillated TEMPO-oxidized celluloses were used for preparation of self-standing films and casting of laminate films on 50 μm thick polyethylene terephthalate. Significant differences between N. spruce and Eucalyptus TOCN were registered. The tensile strength of the films showed a maximum value for spruce samples oxidized with addition of 10 mmol g⁻¹ of NaClO. Oxygen permeability decreased with increasing oxidation levels, being lower for N. spruce TOCN compared to Eucalyptus.     

Inclusion of aramid chains into the layered silicates through solution intercalation route

Aramid–organoclay nanocomposites were fabricated through solution intercalation technique. Montmorillonite was modified with p-amino benzoic acid in order to have compatibility with the matrix. The effect of clay dispersion and the interaction between clay and polyamide chains on the properties of nanocomposites were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing of thin films, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and water uptake measurements. Excessive clay dispersion was achieved even on the addition of high proportions of clay. The structural investigations confirmed the formation of delaminated nanostructures at low clay contents and disordered intercalated morphology at higher clay loadings. The tensile behavior and thermal stability significantly amplified while permeability reduced with increasing dispersibility of organoclay in the polyamide matrix.     

Environmentally Friendly Green Materials from Plant-Based Resources: Modification of Soy Protein using Gellan and Micro/Nano-Fibrillated Cellulose

Fully biodegradable micro/nano-composite resins were prepared by reinforcing soy protein concentrate (SPC) with micro/nano-fibrillated cellulose (MFC) and then blending with gellan. The composite resins showed excellent mechanical and physical properties under testing conditions. Due to the high aspect ratio of MFC, excellent mechanical properties of MFC and MFC/SPC interfacial properties, the SPC (100 parts) reinforced with glycerol (1.5 parts) and MFC (40 parts) showed fracture stress of 88.2 MPa and Young's modulus of about 4.1 GPa, which are higher than those of many conventional petroleum-based plastics. MFC reinforced SPC composite resins were then further modified by blending with gellan to obtain further improvement in fracture stress and Young's modulus. SPC resin containing glycerol (1.5 parts), gellan (40 parts) and MFC (40 parts) had fracture stress of over 122 MPa and Young's modulus of about 5.8 GPa. Although the moisture sensitivity of the specimens was high, they have the potential to replace petroleum-based materials in many fields, particularly for indoor applications.     

Sorption of spruce O-acetylated galactoglucomannans onto different pulp fibres

Sorption of spruce acetylated galactoglucomannans (GGM) onto different pulps, among which unbleached and peroxide-bleached mechanical pulps, and unbleached and bleached kraft (BK) pulps, was studied as a means of understanding the retention of acetylated GGMs in mechanical pulping and papermaking. The fibre surface coverage of lignin and carbohydrates was estimated by X-ray photoelectron spectroscopy (XPS) or electron spectroscopy for chemical analysis (ESCA). GGM sorption was clearly favoured on kraft pulps. Hardly any differences in sorption were, however, observed between unbleached and BK pulps, even if the surface coverage of lignin was lower on the bleached pulp. Neither thermomechanical pulp (TMP) nor chemithermomechanical pulp (CTMP) manufactured from spruce sorbed any acetylated GGMs. Peroxide bleaching of the pulp did not increase sorption. Only CTMP produced from aspen sorbed some GGMs. The anionic charge of neither chemical nor mechanical pulps influenced GGM sorption.     

Preparation and Properties of Biodegradable Spent Tea Leaf Powder/Poly(Propylene Carbonate) Composite Films

The aim of the present work is to develop novel bio-based lightweight material with improved tensile and thermal properties. Spent tea leaf powder (STLP) was used as a filler to improve the tensile and thermal properties of polypropylene carbonate (PPC). Tea is an important material used in hotels and households, and spent tea leaf is a resulting solid waste. Composite films with STLP were obtained by the solution casting method. These films were characterized by optical and scanning electron microscopy, Fourier transform-infrared spectroscopy, thermogravimetric analysis, and tensile testing to examine the effect of filler content on the properties of the composites. The results showed that composite films have increased tensile strength due to enhanced interfacial adhesion between the filler and the matrix. In addition, the composite films also exhibited higher thermal degradation temperatures than pure polypropylene carbonate. The morphology results indicate that there is a good interface interaction between STLP and PPC. Results of the study reveal STLP to be a promising green filler for polymer plastics.     

Investigation on the effect of cellulosic nanoparticles’ morphology on the properties of natural rubber based nanocomposites

Cellulose whiskers and microfibrillated cellulose (MFC) were extracted from the rachis of date palm tree and characterized. These cellulosic nanoparticles were used as reinforcing phase to prepare nanocomposite films using latex of natural rubber as matrix. These films were obtained by the casting/evaporation method. The properties of the ensuing nanocomposite films were investigated using differential scanning calorimetry, toluene and water uptake experiments, dynamic mechanical analysis and tensile tests. The stiffness of the natural rubber was significantly increased above its glass-rubber transition temperature upon nanoparticles addition. The reinforcing effect was shown to be higher for nanocomposites with MFC compared to whiskers. It was ascribed to the higher aspect ratio and possibility of entanglements of the former. The presence of residual lignin, extractive substances and fatty acids at the surface of MFC was also suggested to promote higher adhesion level with the polymeric matrix.     

Dual-functional chitosan–methylisothiazolinone/microfibrillated cellulose biocomposites for enhancing antibacterial and mechanical properties of agar films

In order to enhance the antibacterial and mechanical properties of agar films, the chitosan-methylisothiazolinone (C–MIT) complex was first prepared by the ionic gelation method, and the characterization of the C–MIT complex was carried out by Fourier transform infrared spectroscopy, transmission electron microscopy, and Thermo gravimetry. Chitosan was successfully crosslinked with tripolyphosphate for the nanoencapsulation of methylisothiazolinone, and the C–MIT complex was spherical in shape with a diameter of about 10 nm. The C–MIT/MFC biocomposites obtained through the adsorption of the C–MIT complex on the microfibrillated cellulose (MFC) was then incorporated into the agar films. In comparison with the pure agar films, the tensile strength of the agar composite films was increased by about 19 % at the loading of 10 wt% of C–MIT/MFC biocomposites, and antibacterial tests demonstrated that the agar composite films exhibited remarkable antibacterial activities against both Escherichia coli and Staphylococcus aureus. This work provides a new approach to utilizing multifunctional agar films in the medical field.     

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.     

Investigation of cross-linked PVA/starch biocomposites reinforced by cellulose nanofibrils isolated from aspen wood sawdust

In this study, a bio-based composite prepared from cross-linked polyvinyl alcohol/starch/cellulose nanofibril (CNF) was developed for film packaging applications. For this purpose, CNF, as reinforcing phase, was initially isolated from aspen wood sawdust (AWS) using chemo-mechanical treatments, and during these treatments, hydrolysis conditions were optimized by experimental design. Morphological and chemical characterizations of AWS fibers were studied by transmission electron microscopy, scanning electron microscopy, Kappa number, and attenuated total reflectance-Fourier transform infrared spectroscopy, as well as National Renewable Energy Laboratory and ASTM procedures. Morphological images showed that the diameter of the AWS fibers was dramatically decreased during the chemo-mechanical treatments, proving the successful isolation of CNF. Moreover, chemical composition results indicated the successful isolation of cellulose, and Kappa number analysis demonstrated a dramatic reduction in lignin content. Mechanical, morphological, biodegradability, and barrier properties of biocomposites were also investigated to find out the influence of CNF on the prepared biocomposite properties. The mechanical results obtained from tensile analysis revealed that Young’s modulus and ultimate tensile strength of biocomposite films were enhanced with increasing CNF concentration, while a significant decrease was observed in elongation at break at the same concentration of CNF. Furthermore, with adding CNF, barrier properties and resistance to biodegradability were increased in films, whereas film transparency gradually declined.     

Studies on the properties and characteristics of starch-LDPE blend films using cross-linked, glycerol modified, cross-linked and glycerol modified starch

Corn starch was modified by cross-linking with epichlorohydrin and plasticizer glycerol. X-ray diffraction studies showed that relative crystallinity of the native and cross-linked starch were similar and were not affected by cross-linking. Different films were prepared by blending corn starch, cross-linked starch or glycerol modified starch in LDPE. The mechanical properties of the films were studied for tensile strength, elongation, melt flow index, and burst strength. The properties of the blend films were compared with LDPE films. It was observed that with the blending of 7.5% native starch, there was a decrease in tensile strength, elongation and melt flow index but burst strength increased. The tensile strength, elongation and melt flow index of the films containing cross-linked starch was considerably higher than those containing native starch but the burst strength showed a reverse trend. For native starch and cross-linked starch modified with glycerol, the elongation and melt flow index of the films increased but burst strength decreased. Surface scanning of the blend films were done by scanning electron microscope. Film containing cross-linked starch/glycerol modified starch in the blend was observed to be smoother than the native starch blend films.