Comparison of hydroxypropyl and carboxymethyl guar for the preparation of nanocellulose composite films

The gas barrier and mechanical properties are crucial parameters for packaging materials, and they are highly correlated to the molecular interactions in the polymer matrix. To improve these properties of TEMPO-oxidized cellulose nanofibers (TOCNs) composite films, we studied the effect using hydroxypropyl guar (HPG) or carboxymethyl guar (CMG) in the preparation of TOCN composite films, which were made by following the solution-casting method. The subsequent film characterizations were carried out by UV–Vis spectra, scanning electron microscopy, oxygen and water vapor permeability measurements, tensile and thermogravimetric analyses. SEM results showed that CMG-based films had denser structures than their HPG counterparts. Moreover, the improved hydrogen bonding of the CMG-based films was partially responsible for the improved gas barrier performance, tensile strength and thermal stability. These results support the conclusion that CMG had advantages over HPG when used in the preparation of TOCNs packaging composite films.     

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.     

Rice Husk‐derived Hierarchical Micro/Mesoporous Carbon–Silica Nanocomposite as Superior Filler for Green Electronic Packaging Material

In this study, a carbon‐controllable hierarchical micro/mesoporous carbon–silica material derived from agricultural waste rice husk was easily synthesized and utilized as filler in an epoxy matrix for electronic packaging applications. Scanning electron microscopy, thermogravimetric analysis, and N₂ adsorption/desorption isotherms were used to characterize the morphology, thermal stability, carbon content, and porous structural properties, respectively, of the as‐obtained carbon–silica material, namely rice husk char (RHC ). As a filler material, the uniformly dispersed RHC filler in the epoxy/RHC composite was easily prepared through hydrogen bonding of the silanol group of silica with the epoxy matrix. For electronic packaging applications, the thermal conductivity and thermomechanical properties (storage modulus and coefficient of thermal expansion) of the epoxy/RHC composites improved with increasing carbon content. Moreover, loading of the 40% RHC filler substantially enhanced the storage modulus of the epoxy/RHC composite (5735 MPa ) compared to the epoxy with 40% commercial silica filler (3681 MPa ). Considerable commercial potential is expected for the carbon–silica composite because of the simple synthesis process and outstanding performance of the prepared packaging material.     

Synthesis,properties, and fungal degradation of castor-oil-based polyurethane composites with different cellulose contents

Different contents of bonded cellulose were dispersed in a matrix of castor-oil-based polyurethane to produce composites with high susceptibility to fungal attack. We chose to bond the cellulose filler with free diisocyanate, to increase the crosslinking density. Measurements indicated physical and chemical interactions between the polyurethane matrix and cellulose filler. The cellulose network significantly enhanced the interfacial adhesion and thus improved the thermal stability and Young’s modulus of the composites. The influences of the amount of cellulose on the surface chemical structure, surface morphology, and mechanical properties after fungal attack were also investigated. The tensile strength and elongation at break of these composites substantially decreased after exposure to fungus. These composites with high content of renewable raw materials present an optimal balance of physical properties and biodegradability, with potential applications as ecofriendly biomaterials.     

Tensile Properties and Morphology of Oil Palm Empty Fruit Bunch Regenerated Cellulose Biocomposite Films

The regenerated cellulose (RC)biocomposite films were prepared using casting method where oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were dissolved in N-dimethylacetamide/lithium chloride (DMAc/LiCl)solution. The increasing of OPEFB contents up to 2 wt% increased the tensile strength and modulus of elasticity of RC biocomposite films while the elongation at break decreased. However, at 3 and 4 wt% of OPEFB content, the tensile strength and modulus of elasticity decreased with increases OPEFB content, but elongation at break increased. The increment of tensile strength and modulus of elasticity at 2 wt% is due to the OPEFB fiber that partially dissolved and dispersed with the OPEFB matrix. The morphology studies illustrate that at 2 wt% of OPEFB content of biocomposite films surface consists less voids and agglomerations than at 4 wt%. This can be considered the RC filler was partially dispersed with the RC matrix in the biocomposite films.     

Enhanced Thermal Stability in SiO2/Carbon Filler Derived from Rice Husk via Microwave Treatment for Electronic Packaging Application

Here we report the effect of microwave treatment on a silica–carbon (SiO₂ /C) filler derived from rice husk and the function of the microwave‐treated filler in an epoxy matrix for electronic packaging applications. Thermogravimetric analysis revealed improved thermal stability of the SiO₂ /C filler upon microwave treatment. X‐ray diffraction analysis indicated partial SiC formation after the microwave treatment. For packaging applications, compared to that of the pure epoxy polymer, the thermal conductivity of the epoxy–SiO₂ /C composite was improved by 178% at 40 wt % content of the microwave‐treated SiO₂ /C filler. Furthermore, an improvement of 149% in storage modulus and 17.6°C in glass transition temperature of the epoxy–SiO₂ /C composites was realized. The improvement in thermal stability of SiO₂ /C filler could be achieved via a simple microwave treatment, which in turn enhanced the thermal stability, thermal conduction, and thermomechanical strength of the electronic packaging materials.     

Development and analysis of biodegradable poly(propylene carbonate)/tamarind nut powder composite films

Using biodegradable polypropylene carbonate as the matrix and the tamarind nut powder (TNP) in 5–25?wt% as the filler, the biocomposites were prepared. The biocomposites were characterized by Fourier transform infrared, X-ray diffraction, and thermogravimetric analysis techniques. The distribution of the TNP in the biocomposites was examined by polarized optical microscope. The tensile strength of the biocomposite films was higher than that of the matrix and increased with filler content whereas a reverse trend was observed in % elongation at break. These films with increased tensile strength can be considered for packaging applications.     

Nanocellulose reinforced as green agent in polymer matrix composites applications

Owing to their abundance, high strength and stiffness, and low weight and biodegradability, nanocellulose (NC) is regarded as a promising candidate for the preparation of green composites. The high reinforcing effect assigned to the mechanical percolation phenomenon of NC is due to the stiff continuous networks of cellulosic nanoparticles linked via hydrogen bonding. Compared to nanocrystalline cellulose, NC fibers result in more significant improvement to the modulus, stiffness, and strength as aspect ratio NC fiber is higher compared to NC crystal. Indeed, in the case of biopolymer composites, the reinforcement effect of NC is attributed to the NC‐polymer interactions and the reinforcing effect occurring through effective stress transfer at the NC‐polymer interface. The NC‐reinforced composites tend to become more brittle as the concentration of the reinforcing particles increase up to the saturated level, due to the reduction in surface adhesion between filler and matrix. Due to its promising mechanical and structural stability, NC composites have been used widely in many industrial applications such as food packaging, electronic applications, and tissue engineering.     

Biocomposites based on Alfa fibers and starch‐based biopolymer

Biocomposite materials based on Alfa cellulose fibers (esparto grass plant) as reinforcing element and starch‐based biopolymer matrix were prepared and characterized in terms of mechanical performance, thermal properties, and water absorbance behavior. The fibers and the matrix were first mixed in the melted state under mechanical shearing using a plastograph and the obtained composites were molded by injection process. The tensile mechanical analysis showed a linear increase of the composite flexural and tensile modulus upon increasing the fiber content, together with a sharp decrease of the elongation at break. The fibers′ incorporation into the biopolymer matrix brings about an enhancement in the mechanical strength and the impact strength of the composite. Dynamic mechanical thermal analysis (DMTA) investigation showed two relaxations occurring at about ?30 and 35°C. The addition of Alfa fibers enhanced the storage modulus E′ before and after T_α, which is consistent with the reinforcing effect of Alfa cellulose fibers. Copyright © 2008 John Wiley & Sons, Ltd.     

Sustainable composites of surface-modified cellulose with low–melting point polyamide

The present study proposed a series of sustainable polyamide/cellulose composites with up to 60% bio-based content to address environmental issues arising from using fossil-based polymers. Furthermore, it addressed one of the most challenging cellulose/polymer composites' issues, filler/matrix compatibility. Accordingly, the microcrystalline cellulose (MCC) surface was treated through the grafting of n-octadecyl isocyanate (ODI) molecules. The elemental analysis confirmed the substitution of approximately 9 ODI molecules per 100 anhydroglucose units, resulting in superhydrophobic MCC formation with a water contact angle of 130°. The surface-modified MCC was melt blended with a bio-based low–melting point polyamide, developed through copolymerization of 11-aminoundecanoic acid and 12-aminolauric acid. Scanning electron microscopy images confirmed no evidence of surface-modified MCC agglomeration, even at a high loading of 30 wt%, suggesting a uniform dispersion of the filler particles and excellent compatibility between two phases. Consequently, the storage modulus, tensile modulus, and yield stress were enhanced by 40%, 100%, and 50%, respectively, in the composite sample with 30 wt% of MCC, proving excellent stress transformation from the matrix to particles arose from good adhesion between cellulose particles and polyamide chains. Furthermore, all samples revealed suitable melt flowability and viscoelastic performances, suggesting their excellent processability, a critical property for engineered thermoplastics. On top of that, the presence of the surface-modified particles considerably decreased water uptake capacity and water vapor transmission of the polymer matrix, making it interesting for specific applications like packaging films.     

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.     

Sustainable nanocomposite films based on bacterial cellulose and pullulan

Bionanocomposites with improved properties based on two microbial polysaccharides, pullulan and bacterial cellulose, were prepared and characterized. The novel materials were obtained through a simple green approach by casting water-based suspensions of pullulan and bacterial cellulose and characterized by TGA, RDX, tensile assays, SEM and AFM. The effect of the addition of glycerol, as a plasticizer, on the properties of the materials was also evaluated. All bionanocomposites showed considerable improvement in thermal stability and mechanical properties, compared to the unfilled pullulan films, evidenced by the significant increase in the degradation temperature (up to 40 °C) and on both Young’s modulus and tensile strength (increments of up to 100 and 50%, for films without glycerol and up to 8,000 and 7,000% for those plasticized with glycerol). Moreover, these bionanocomposite films are highly translucent and could be labelled as sustainable materials since they were prepared entirely from renewable resources and could find applications in areas as organic electronics, dry food packaging and in the biomedical field.     

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.     

Structure and properties of regenerated cellulose/tourmaline nanocrystal composite films

Nanocomposite films were successfully prepared from cellulose and tourmaline nanocrystals with mean diameters of 70 nm in a 1.5 M NaOH/0.65 M thiourea aqueous solution by coagulation with 5 wt % CaCl₂ and then a 3 wt % HCl aqueous solution for 2 min. The structure and properties of the composite films were characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile testing. The results indicated that the tourmaline nanocrystals were dispersed in a cellulose matrix, maintaining the original structure of the nanocrystals in the composite films. The loss peaks (tan δ) in the DMA spectra and the decomposition temperatures in the DSC curves of the composite films were significantly shifted toward low temperatures, suggesting that the nanocrystals broke the partial intermolecular hydrogen bonds of cellulose, and this led to a reduction in the thermal stability. However, the nanocomposite films exhibited a homogeneous structure and dispersion of the nanocrystals. When the tourmaline content was in the range of 4–8 wt %, the composite films possessed good tensile strength (92–107 MPa) and exhibited obvious antibacterial action against Staphylococcus aureus. This work provides a potential way of preparing functional composite films or fibers from cellulose and nanoinorganic particles with NaOH/thiourea aqueous solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 367–373, 2004     

Tensile,thermal, and antibacterial characterization of composites of cellulose/modified Pennisetum purpureum natural fibers with in situ generated copper nanoparticles

Eco-friendly all cellulose composites were developed using cellulose as matrix and nanocomposite (in situ generated copper nanoparticles modified Napier Grass Fibers (NGFs)) as fillers for the antibacterial applications. The content of the nanocomposite filler was increased from 1?wt.% to 5?wt.% in the cellulose matrix. All these composites were characterized by Scanning Electron Microscopy (SEM), Tensile, Thermo Gravimetric Analysis (TGA), and antibacterial tests. SEM-EDX analysis revealed the in situ generation of copper nanoparticles on the surface of the films. Further, all cellulose composites showed good thermal stability. A minimum of 30% increase in char residue was observed in all cellulose nanocomposites compared to matrix. Antibacterial analysis indicated an excellent clear zone formation against both Gram Negative (Escherichia coli) and Gram Positive (Staphylococcus) bacteria. Hence, all these cellulose nanocomposite films can be considered as antibacterial packaging and dressing materials in medical field.     

Reinforcement of aligned cellulose fibers by lignin-polyester copolymers

With an ever-increasing attention on the climate change and the growing amount of plastic wastes generated, the search for an alternative to the petroleum-based plastics has never been as imperative. Inspired by the structure of natural wood, we aim to reproduce artificial equivalent using modified lignin and cellulose acetate. As natural wood are made up of an aggregation of fibers, electrospinning was used to produce the fiber component. Besides exploring the influence of various polymers on the properties of the eventual fibers, its properties were also examined in terms of its orientation – random and aligned. The addition of lignin copolymers was shown to remarkably improve the tensile strength and the Young’s modulus of cellulose acetate fibers up to 500% and 7,000% respectively. In contrast to the random fibers, the aligned fibers demonstrated better tensile strength and Young’s modulus which could be attributed to the higher crystallinity. Among the fibers, the longitudinal aligned C.A. + Lig-PHB fibers exhibited the best tensile strength and Young’s modulus which could be explored for load bearing 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.     

Improved Hydrophobicity of Macroalgae Biopolymer Film Incorporated with Kenaf Derived CNF Using Silane Coupling Agent

Hydrophilic behaviour of carrageenan macroalgae biopolymer, due to hydroxyl groups, has limited its applications, especially for packaging. In this study, macroalgae were reinforced with cellulose nanofibrils (CNFs) isolated from kenaf bast fibres. The macroalgae CNF film was after that treated with silane for hydrophobicity enhancement. The wettability and functional properties of unmodified macroalgae CNF films were compared with silane-modified macroalgae CNF films. Characterisation of the unmodified and modified biopolymers films was investigated. The atomic force microscope (AFM), SEM morphology, tensile properties, water contact angle, and thermal behaviour of the biofilms showed that the incorporation of Kenaf bast CNF remarkably increased the strength, moisture resistance, and thermal stability of the macroalgae biopolymer films. Moreover, the films’ modification using a silane coupling agent further enhanced the strength and thermal stability of the films apart from improved water-resistance of the biopolymer films compared to unmodified films. The morphology and AFM showed good interfacial interaction of the components of the biopolymer films. The modified biopolymer films exhibited significantly improved hydrophobic properties compared to the unmodified films due to the enhanced dispersion resulting from the silane treatment. The improved biopolymer films can potentially be utilised as packaging materials.     

Properties of ethylene propylene diene rubber/white and black filler composites cured by gamma radiation in presence of sorbic acid

The effect of incorporating sorbic acid (SA), an echo-friendly curing agent, and silica or carbon black (CB) filler, as well as gamma irradiation on the physico-chemical, mechanical and thermal properties of ethylene propylene diene monomer rubber (EPDM) was investigated. The results indicated that the developed composites revealed improvement in the studied parameters over the untreated samples. Filler incorporation into rubber matrix has been proven a key factor in enhancing the swelling resistance, tensile strength and thermal properties of the fabricated composites. The improvement in tensile strength and modulus was attributed to better interfacial bonding via SA. Alternatively, a comparison was established between the performance of the white and black fillers. The utmost mechanical performance was reported for the incorporated ratios 10 phr SA and 40 phr white filler into a 50 kGy irradiated composite. Meanwhile, the incorporation of CB yielded better thermally stable composites than those filled with silica at similar conditions.     

Fabrication of thermoplastic polyurethane composites with a high dielectric constant and thermal conductivity using a hybrid filler of CNT@BaTiO3

Thermoplastic polyurethane composites with an excellent dielectric constant and high thermal conductivity were obtained using CNT@BaTiO₃ as a filler through a low-speed melt extrusion method. Before preparing the hybrid filler for the composite, the filler particles were surface modified to ensure that the outer surfaces could facilitate the reaction among particles to form the hybrid and ensure complete dispersion in the thermoplastic polyurethane matrix. After confirming the proper surface treatment of the filler particles using infrared spectroscopy, thermal degradation analysis and field emission scanning electron microscopy, they were used to prepare the composite materials at a processing temperature of 200 °C. The thermal stability, thermomechanical properties, mechanical properties, thermal conductivity, and dielectric properties of the composites were investigated. Compared to the neat thermoplastic polyurethane matrix, the prepared composite exhibited a higher thermal stability, approximately 300% higher storage modulus, higher tensile strength and elongation at break values, approximately three times higher thermal conductivity (improved from 0.19 W/(m.K) to 0.38 W/(m.K), and approximately five times larger dielectric constant at high frequencies (at 1 MHz a dielectric constant of 19.2 was obtained).