Search

Cellulose-based paper is an alternative substitution for petroleum-based polymers for packaging applications, but its mechanical performance is poor when in contact with water. Herein, chitosan was applied on cellulose-based paper via a coating approach. The effects of chitosan coatings between none and five layers on the color properties, wettability, thermal properties, mechanical performance, and overall migration in food simulants of the paper were evaluated. After the application of chitosan, chitosan first filled cavities between cellulose fibers within a network, and the chitosan film was formed on the paper surface later. This resulted in a pronounced increase in wettability and mechanical properties associated with a loss of whiteness and an increase in yellowness of the coated paper. The chitosan-coated paper became hydrophobic with a water contact angle of 94.7 ± 2.8°, and a robust improvement of 156.4% for tensile strength and 114.8% for strain at break was observed for the paper coated with three layers of chitosan in wet conditions in comparison to the uncoated paper. A reduction in the migration of the low molecular residuals from the paper could be hindered by the chitosan coating. These enhanced features revealed that chitosan-coated paper could be used as a food-contact material.

Since last decades, nanocellulose has gained much attention in nanocomposite foams owing to high stiffness and strength, renewability, sustainability and biodegradability. Nanocellulose is hydrophilic, and could be easily dispersed in hydrophilic polymer matrices; however, there are challenges to introduce nanocellulose in less hydrophilic polymers. This review addresses the development of polymer nanocomposite foams with plant-based nanocellulose (cellulose nanofibers and cellulose nanocrystals), and the chemical modification and mechanical approaches to enhance the dispersibility of nanocellulose in hydrophobic polymer matrices. The combination of nanocellulose and other nanoparticles such as graphene nanoplatelets, montmorillonite clay, carbon nanotubes and zeolites to yield multifunctional porous nanocomposite materials with promising features such as self-extinguishment, dye adsorption, microwave absorption, conductivity and biocompatibility is also discussed in this paper.

Macaranga hypoleuca, a lesser-known and rarely used wood species, is a pioneer species in the secondary succession that is classified as a fast-growing plant with long fibers. M. hypoleuca was composed of holocellulose, lignin, and extractives, at contents of 68.1 ± 0.5%, 25.5 ± 0.6%, and 4.7 ± 0.1%, respectively. In this study, refined M. hypoleuca pulp was treated by alkali treatment, delignification, and maleic acid hydrolysis. The pre-treated pulp was further disintegrated by mechanical treatment, which produced nanofibrillated cellulose (NFC) with a yield of 53.5 ± 2.7%. The average diameter of the NFC was 43.0 ± 4.9 nm. The use of maleic acid (C4H4O4) hydrolysis also reduced the hydrophilicity of the NFC, as confirmed by the Fourier-transform infrared (FTIR) spectra. It was determined that the Macaranga tree is a suitable lignocellulose source to produce NFC, which can be used in transparent flexible substrates, coating, and composite applications.

Water hyacinth (Eichhornia crasspies) was used as a renewable cellulose source to prepare nanofibrillated cellulose (NFC). Due to the porous structure and low lignin content of water hyacinth, a 10...

Cellulose, the most abundant biopolymer on Earth, has been widely attracted owing to availability, intoxicity, and biodegradability. Environmentally friendly hydrogels were successfully prepared from water hyacinth-extracted cellulose using a dissolution approach with sodium hydroxide and urea, and sodium tetraborate decahydrate (borax) was used to generate cross-linking between hydroxyl groups of cellulose chains. The incorporation of borax could provide the superabsorbent feature into the cellulose hydrogels. The uncross-linked cellulose hydrogels had a swelling ratio of 325%, while the swelling ratio of the cross-linked hydrogels could achieve ~ 900%. With increasing borax concentrations, gel fraction of the cross-linked hydrogels increased considerably. Borax also formed char on cellulose surfaces and generated water with direct contact with flame, resulting in flame ignition and propagation delay. Moreover, the cross-linked cellulose-based hydrogels showed antibacterial activity for gram-positive bacteria (S. aureus). The superabsorbent cross-linked cellulose-based hydrogels prepared in this work could possibly be used for wound dressing, agricultural, and flame retardant coating applications.

The extraction of cellulose nanofibers (CNFs) from a lignocellulosic source containing less lignin would be an effective way to avoid repetitious and energy-consuming chemical treatments. In the pr...

This study focused on preparation of microfibers from bamboo culms using steam explosion with and without chemical treatments, and utilization of the isolated fibers in formation of bamboo paper fabricated with nanofibrillated cellulose (NFC). Compared with those obtained from the steam explosion alone (S), the bamboo microfibers isolated using the steam explosion followed by bleaching process (S/A) exhibited a significantly reduced fiber width of 7.5 μm and a markedly increased cellulose content of 97.85%. The S/A fiber showed an increased decomposition temperature, corresponding with lower contents of hemicellulose and lignin than those of the S fiber. The S/A microfibers were subsequently proceeded to paper formation. Physical and mechanical properties of the paper with an introduction of different NFC concentrations (0–50 wt%) were investigated. The linear relationship between the density, porosity and mechanical properties of the paper and NFC contents was observed. The more the NFC content, the greater the density and the lower the porosity the paper exhibited. At 50 wt% NFC, the paper density increased to 0.64 g cm−3, and the paper porosity decreased to 57.0% whereas the paper without NFC showed a density of 0.39 g cm−3 and porosity of 73.6%. Tensile strength and strain of the paper composed with 50 wt% NFC were 10-fold and 3-fold, respectively, greater than those of the paper without NFC. The addition of NFC could manifest paper mechanical properties and porosity within the paper structure, which would be useful for scaffold and membrane applications. Keywords: Bamboo, Mechanical properties, Paper, Nanofibrillated cellulose, Steam explosion, Microfibers, Nanofibers

Cellulose, the most abundant polysaccharide on Earth, has a number of desirable properties, including availability, biodegradability, low cost, and low toxicity and has been used in a variety of applications. Recently, all-cellulose composite materials have been made from a wide variety of cellulose sources, including wood and agricultural wastes, via impregnation or partial surface dissolution approaches utilizing a specific solvent. Due to the improved interfacial interactions between the cellulose matrix and cellulose reinforcement, all-cellulose composites exhibit superior mechanical properties when compared to biopolymers and petroleum-based polymers. The current article discusses the factors affecting the mechanical properties and interfacial bonding of all-cellulose composites. Additionally, the incorporation of inorganic nanoparticles is described to enhance the multi-functional properties of all-cellulose composites, such as their conductivity, permeability, and adsorption. Furthermore, this review summarizes the potential applications of all-cellulose composites in the following areas: composites, packaging, aerogels, hydrogels, fibers, tissue engineering, membranes, textiles, and coatings.

Two different types of cellulose nanocrystals, derived from water hyacinth fibers and microfibrillated cellulose (MFC), were prepared using an acid hydrolysis treatment. These cellulose nanocrystals (CNCs) were further used as barrier enhancing fillers for polyurethane (PU) blended with 25 wt% of poly(vinylidene dichloride) (PVDC). The aim of this study was to investigate the effects of types and concentration of CNCs on mechanical, optical and barrier properties of polymer composite films. The feasibility of applying the obtained composite films as an encapsulating material for enhancing the lifetime of dye sensitized solar cells (DSSC) was also of interest. The acid hydrolysis of the MFC-yielded rod-shaped cellulose nanocrystals (CNCm) while the acid-hydrolyzed water hyacinth led to a formation of spherical-shaped cellulose nanocrystals (CNCw). Regardless of the types of CNCs, the optical transparency of the composite films was maintained well above 60%. According to results in this study, the most efficient film with the lowest water vapor transmission rate of 0.0517 g m−2 day−1 was the PU/PVDC film reinforced with 0.1 wt% of CNCm. The encapsulants made from this composite could prolong the lifetime of the DSSC devices for up to 14 days, with the normalized PCE value of 0.78. Overall, this work showed that the considerations of the barrier properties of the polymer encapsulants alone are insufficient to ensure that the system would be effective. An interfacial adhesion between the encapsulants and the electrodes, as well as some side reactions between polymers and chemicals inside the fabricated cell, should also be taken into account.

The reinforcing abilities of cellulose microfibers and nanofibrillated cellulose (NFC) in poly(lactic acid) (PLA) were evaluated. NFC successfully prepared from regenerated cellulose fibers using high-speed blending for 60 min was introduced in a PLA matrix. The physical and mechanical properties of NFC-reinforced PLA composites were investigated in comparison with those of the composites with microfibers. NFC fibrils with diameters in the range of 100–500 nm were disintegrated from micron-sized regenerated fibers. A slight decrease in the degree of crystallinity and degradation temperature obtained for NFC after mechanical treatment was found compared with untreated microfibers. The introduction of NFC in the PLA effectively increased the tensile strength and Young’s modulus of the composites by 18% and 42%, respectively. The use of micron-sized fibers to reinforce PLA, on the other hand, showed a slight improvement in Young’s modulus (13%). The improvement in the mechanical properties of the composites reinforced with NFC was found because of the higher surface area of NFC and better interaction between the matrix and NFC fibrils. This allowed stress to transfer from the matrix to the reinforcement. NFC prepared using the high-speed blending could be an alternative to use as reinforcement in composites.

s Pineapple leaves are left as waste in many countries such as Thailand, Brazil, and the Philippines. However, due to its high cellulose content, it can be utilized as raw material for the synthesis of nanocelluloses (CNCs) using extraction. The mechanical properties were studied of reinforcing composite from pineapple leaves with and without fillers vulcanized using electron beam irradiation (EB) and sulfur vulcanization (S-vul). The extraction was performed using acid hydrolysis. The CNCs were rod-like in shape with a diameter and length of approximately 100–150 nm and 3–5 nm, respectively. The CNCs were used as reinforcing fillers in natural rubber (NR) composites. The results showed that loading CNCs at 2.5 phr in NR composites enhanced their mechanical properties due to the good distribution of the CNCs in the composites. Furthermore, the composites vulcanized using sulfur (S-vul) were stronger and had better chemical resistance than those using EB irradiation. This was related to the amount of crosslinking networks in the composites.

Pineapple leaf fibers with diameters of 43 ± 0.1 µm were treated by two different approaches: the alkaline treatment and the combination of the steam explosion and alkaline treatment. The observations revealed the steam explosion process efficiently provided 3.4 µm diameter fibers with a less amount of lignin and a higher proportion of cellulose, compared with the alkaline-treated fibers. The steam-exploded fibers showed higher crystallinity and more thermal stabilities than the alkaline-treated fibers. No structural change from cellulose I to cellulose II was detected from both treated pineapple leaf fibers. Subsequently, all-cellulose composite laminates were prepared from these two types of treated pineapple leaf fibers mats. The higher tensile strength and modulus were obtained from the steam-exploded pineapple leaf fibers composite laminates due to larger surface areas of the fibers interacted with the cellulose matrix. Fracture morphology of the composites was studied after tensile deformation. The combination mechanism of fiber breakage and fiber pull-out deformation was observed from the steam-exploded pineapple leaf fibers composite laminates, whereas only fiber pull-out mechanism was found from the alkaline-treated pineapple leaf fibers composite laminates. The fiber width and amounts of the matrix filling in pores in a mat were found to dominate the mechanical properties of the all-cellulose composites.

Chitosan with low (25 kDa) and high molecular weight (2100 kDa) were used to enhance performances of paper made from steam-exploded bamboo fibers and nanofibrillated cellulose. Chitosan solutions with concentrations of 0–1.0 wt% were manually applied on paper surface using a facile coating approach with a wire bar. Effects of chitosan coatings on morphology, thermal stability, wettability, mechanical performances and antibacterial properties of the paper were investigated. The larger improvement in the mechanical properties and wettability of the chitosan coated paper was observed with increasing concentrations of chitosan due to the disappearance of empty pores between fibers within a cellulose network by the formed chitosan matrix. These improvements were significantly higher when high molecular weight chitosan was applied. Yet, the addition of chitosan slightly decreased the thermal stability of the coated paper, and the chitosan coating did not improve the antimicrobial properties of the paper. The antimicrobial activity of chitosan against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) was found to be diminished when a chitosan solution was entrapped within paper. Together with the overall migration of the paper in food simulants, the results suggested that the chitosan coated paper could be applied for non-food-direct-contact packaging materials.

Cellulose nanocrystal (CNC) reinforced poly(vinyl alcohol) (PVA) hydrogels with a water content of ∼92% were successfully prepared with glutaraldehyde (GA) as a cross-linker. The effects of the CNC content on the thermal stability, swelling ratio and mechanical and viscoelastic properties of the cross-linked hydrogels were investigated. The compressive strength at 60% strain for the hydrogels with 1 wt% CNCs increased by 303%, from 17.5 kPa to 53 kPa. The creep results showed that the addition of CNCs decreased the creep elasticity due to molecular chain restriction. The almost complete strain recovery (∼97%) after fixed load removal for 15 min was observed from the hydrogels with CNCs, compared with 92% strain recovery of the neat cross-linked PVA hydrogels. The incorporation of CNCs did not affect the swelling ratio and thermal stability of the hydrogels. These results suggest the cross-linked CNC-PVA hydrogels have potential for use in biomedical and tissue engineering applications.

This review addresses the recent developments of the processing of cellulose nanocomposites, focusing on the most used techniques, including solution casting, melt-processing of thermoplastic cellulose nanocomposites and resin impregnation of cellulose nanopapers using thermoset resins. Important techniques, such as partially dissolved cellulose nanocomposites, nanocomposite foams reinforced with nanocellulose, as well as long continuous fibers or filaments, are also addressed. It is shown how the research on cellulose nanocomposites has rapidly increased during the last 10years, and manufacturing techniques have been developed from simple casting to these more sophisticated methods. To produce cellulose nanocomposites for commercial use, the processing of these materials must be developed from laboratory to industrially viable methods.

Poly(vinyl alcohol) (PVA) foams reinforced with cellulose nanocrystals (CNCs) were prepared with formaldehyde as a crosslinking agent. Two initial reaction times (10, 120 s) and the addition of CNCs (0–2 wt% based on total reaction suspension) were found to affect the foam density, water uptake, morphology and mechanical properties. A longer initial reaction time resulted in higher mechanical properties and density, due to the small pore size. The addition of CNCs induced a progressive decrease in the pore diameter and an increase in the foam density, as well as improved mechanical properties. With 1.5 wt% CNC content, the compressive strength of the PVA foams was significantly improved from 7 to 58 kPa for 10 s-initial reaction time and from 65 to 115 kPa for 120 s-initial reaction time. Results showed that the cross-linked PVA foams with CNC had promising properties for use in biomedical applications.

This research work has concerned the development of volatile organic compounds (VOCs) removal filters from biomaterials, based on keratin extracted from chicken feather waste and poly(lactic acid) (PLA) (50/50%w/w) blend. Clay (Na-montmorillonite) was also added to the blend solution prior to carrying out an electro-spinning process. The aim of this study was to investigate the effect of clay content on viscosity, conductivity, and morphology of the electrospun fibers. Scanning electron micrographs showed that smooth and bead-free fibers were obtained when clay content used was below 2 pph. XRD patterns of the electrospun fibers indicated that the clay was intercalated and exfoliated within the polymers matrix. Percentage crystallinity of keratin in the blend increased after adding the clay, as evidenced from FTIR spectra and DSC thermograms. Transmission electron micrographs revealed a kind of core-shell structure with clay being predominately resided within the keratin rich shell and at the interfacial region. Filtration performance of the electrospun keratin/PLA fibers, described in terms of pressure drop and its capability of removing methylene blue, were also explored. Overall, our results demonstrated that it was possible to improve process-ability, morphology and filtration efficiency of the electrospun keratin fibers by adding a suitable amount of clay.

Pineapple leaf microfibers (PALM) were used to prepare all-cellulose composites using the surface selective dissolution method. Effect of dissolution times on mechanical and physical properties of the all-cellulose composites was investigated. The structural transformation from cellulose I to cellulose II was observed when the fibers were dissolved in a mixed solution of lithium chloride (LiCl) and N,N-dimethylacetamide (DMAc). Values of 42.8 MPa and 1.2 GPa for tensile strength and Young's modulus, respectively, were obtained from the composites with 120 min dissolution time in the LiCl/DMAc solution, whereas the tensile strength and Young's modulus of the undissolved PALM mats were found to be only 1.5 MPa and 0.1 GPa, respectively. The failure mechanism of the composites was changed from the fiber pull-out to the fiber breakage when the dissolution time was longer. However, lower thermal stability and degree of crystallinity of the composites were caused by the change of the cellulose structure. The composites prepared in this work can be called as biodegradable materials, and could be the potential candidates to replace nonbiodegradable materials. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

How do trees support their upright massive bodies? The support comes from the incredibly strong and stiff, and highly crystalline nanoscale fibrils of extended cellulose chains, called cellulose nanofibers. Cellulose nanofibers and their crystalline parts-cellulose nanocrystals, collectively nanocelluloses, are therefore the recent hot materials to incorporate in man-made sustainable, environmentally sound, and mechanically strong materials. Nanocelluloses are generally obtained through a top-down process, during or after which the original surface chemistry and interface interactions can be dramatically changed. Therefore, surface and interface engineering are extremely important when nanocellulosic materials with a bottom-up process are fabricated. Herein, the main focus is on promising chemical modification and nonmodification approaches, aiming to prospect this hot topic from novel aspects, including nanocellulose-, chemistry-, and process-oriented surface and interface engineering for advanced nanocellulosic materials. The reinforcement of nanocelluloses in some functional materials, such as structural materials, films, filaments, aerogels, and foams, is discussed, relating to tailored surface and/or interface engineering. Although some of the nanocellulosic products have already reached the industrial arena, it is hoped that more and more nanocellulose-based products will become available in everyday life in the next few years.

Optically transparent tough cellulose nanofiber (CNF) reinforced composites were successfully prepared through a simple Pickering emulsion method. The emulsions of CNFs, acrylic resin monomer and water were vacuum filtered to form mats, and the mats were hot-pressed, and UV-cured. Hierarchical CNF networks where the homogenously-dispersed CNFs formed a network surrounding resin droplets in the composites were observed. As the CNF content increased, thicker CNF networks were formed, which could bear greater loads. The strength, modulus, strain and toughness of the composites with 25 wt% CNFs increased to be 18.6, 56.7, 1.5, and 36.3 times as great as those of the neat acrylic films with the great reduction in the thermal expansion to 7.3 ppm K−1 (1/26th of the neat polymer) and only 3% degradation in optical transmittance. The composites prepared by the Pickering emulsion approach showed higher performances than those from the impregnation method, which could be used in optoelectronic applications.

The recent rapid expansion of thin-film, bendable, and wearable consumer (opto)electronics demands flexible and transparent substrates other than glass. Plastics are the traditional choice, but they require amelioration because of their thermal instability. Here, we report the successful conversion of a soft and thermally vulnerable polymer into a highly thermally stable transparent nanocomposite material. This is achieved by the meticulous choice of a polymer with a glass-transition temperature below 0 °C that gives stable mechanics above room temperature, reinforcing the polymer with a load-bearing hierarchical network of the incredibly strong and stable natural material: cellulose nanorods. Owing to the Pickering emulsification process, the nanocomposites inherit the self-assembled structural hierarchy from the cellulose nanorod-encapsulated resin droplets. The ameliorated nanocomposites have highly desirable high-temperature endurance (∼150-180 °C) in terms of the thermomechanical, thermodimensional, and thermo-optical performance. Any photonic nano- or microstructures can be directly molded on the surface of the nanocomposites in high precision for better light management in photonic and opto-electronic applications. The highlight of this work is the demonstration of a highly thermally stable microlens array on the ameliorated transparent nanocomposite.

Journal of Metals Materials and Minerals, 29, 2, 110-114

Cellulose nanofibers (CNFs) with width of 20 nm and lengths of up to several µm were fully disintegrated from water hyacinth (Eichhornia crassipes) with aids of the 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation and mild-mechanical treatment. TEMPO-oxidized CNFs were characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). FTIR reveals the conversion of C-6 hydroxyl groups to sodium carboxylate groups, and lower thermal degradation was obtained from the TEMPO-oxidized CNFs in comparison to untreated cellulose fibers. The as-prepared TEMPO-oxidized CNFs might be possibly used in packaging and composite applications.

The aim of this work is to compare properties of cellulose mats from pineapple leaf fibers with and without using the steam explosion method. Pineapple leaf fibers were divided into two groups. The first group was chemically treated with sodium hydroxide for 24 h, and directly used to prepare cellulose mats. The other group was pre-treated by steam explosion before treating with sodium hydroxide. Cellulose mats of microfibers were then prepared. The structure of pineapple leaf fibers was found to be changed due to the steam explosion observed by scanning electron microscopy. The effect of the steam explosion treatment was studied from chemical composition of steam-exploded fibers and unsteam-exploded fibers. Mechanical properties of mats of steam-exploded fibers were also investigated, compared to those of unsteam-exploded fiber mats. Mechanical properties of the mats of steam-exploded fibers were higher than those of the mats of unsteam-exploded fibers. This is due to the fact that the smaller-size fibrils can be found in the steam-exploded fibril mats.

Solar cell encapsulating film based on ethylene vinyl acetate copolymer (EVA) was modified by using bacterial cellulose (BC) nanofibres. Bacterial cellulose was chemically modified with propionic a ...

Pineapple leaf microfibers were firstly prepared using steam explosion, and all-cellulose composites were subsequently prepared using a surface selective dissolution process with the solvent of lithium chloride and N,N-dimethylacetamide (LiCl/DMAc). Mechanical properties and surface morphology of all-cellulose composites with immersion times of pineapple leaf microfibers in the solvent of LiCl/DMAc were investigated using tensile testing and scanning electron microscopy, respectively. The tensile strength of the all-cellulose composites with 120 min-immersion time was approximately 28 times higher than that of the pineapple leaf microfiber mats. These biocomposites made from pineapple leaf microfibers could be one of the potential alternatives to replace glass fiber reinforced composites.

Poly(vinyl alcohol) (PVA) foams were prepared using a green lyophilization process without the use of foaming agents. PVA solutions with contents of CNCs (1–4 wt%) were prepared at two different freezing temperatures (−20 and −186 °C). With the addition of CNCs, moisture uptake of the CNC-PVA foams prepared at two freezing temperatures was lower than the neat PVA foams. With increasing CNC contents, no significant change of the moisture uptake could be observed for both types of the foams. Similar values of the moisture uptake could be found from both foams frozen at −20 and −186 °C. Scanning electron microscope measurements revealed the aligned-porous-structure of the foams frozen at −186 °C along with the ice growth direction while large and elongated pores were observed from the foams with the lower freezing temperature. These unique features of the foams prepared by a freeze-drying technique could be controlled by changing the freezing temperature, and these foams could be useful for specific applications such as tissue engineering scaffolds, thermal insulators or filters.

Journal of Metals, Materials and Minerals, 28, 1, 10-15

Macaranga hypoleuca is one of the potential native species for natural fibers consisting of long fibers. In M. hypoleuca pulp the main majority is cellulose, followed by hemicellulose and lignin. Based on these characters, it is possible to prepare cellulose nanofibers (CNFs) from M. hypoleuca pulp. In this work, CNFs were prepared by the combination of the chemical and mechanical treatments. Those were acid hydrolysis by sulfuric acid and ultrasonication machine forwarded. The aims studies observed the potential of M. hypoleuca pulp as a raw material of CNFs and characteristics of CNFs from M. hypoleuca pulp. The results showed of the CNFs had widths of 42 ± 7.27 nm and crystallinity of 76.9%. The decomposition temperature of the CNFs was of 332 °C. This could be value added to M. hypoleuca trees, and the CNFs extracted from this M. hypoleuca pulp might be useful for composite applications.

Combined homogenisation and sonication treatments of micron-sized lyocell fibres were used to generate microfibrillated cellulose (MFC) with fibril diameters of ∼350 nm. No further reduction in fibril diameter was observed after 30 min treatment. Poly(vinyl alcohol) (PVA) composites reinforced with these fibrils were fabricated using solvent casting and physical and mechanical properties were investigated. The presence of MFC in PVA increased the thermal degradation of the polymer. An increase in both the tensile strength and modulus of the composites was observed for up to 3 wt.% of fibrils; beyond this point no significant increases were observed. An estimate of ∼39 GPa is made for the fibril modulus based on this increase. Stress-transfer between the polymer resin and the fibrils was investigated using Raman spectroscopy. Stress transfer in the composite is shown to be greater than that of a pure network of fibres, indicating a good fibre–matrix bond.

This research will thus try to broaden the properties of bioplastics to be used as smart materials. Cellulose nanowhiskers will be initially prepared from different cellulose source and its morphology will be investigated. Water-activated shape memories nanocomposites will be consequently prepared from the obtained cellulose nanowhiskers and three polymers those are PBS and PBAT. The mechanical, physical and morphological will be investigated. The influences of cellulose nanowhiskers and their morphology on water-activated shape memory behavior will be studied.Recently, natural fiber have extensively used as reinforcement materials in polymeric nanocomposite due to environment concerns. Cellulose nanowhisker (CNWs) have also attracted much attention as environmentally friendly nanofillers for polymer composites. Cellulose nanowhiskers were extracted from commercial source, paper filter and alpha cellulose, using acid hydrolysis by sulfuric acid with various hydrolysis times (20,45,70,95,120 minutes), temperature (35,45,60°C). The hydrolyzed cellulose was neutralized with two different techniques, dialysis and titration. The samples were then sonicated and dried with a freeze dryer. The effects of preparation conditions on the morphological of cellulose nanowhisker were investigated. Cellulose nanowhisker powders were characterized scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results showed that it was possible to obtain ultrathin cellulose nanowhiskers with diameters as low as 9 nm. A possible correlation between preparation conditions and particle size was not observed but titration technique time process was reduced.

In this research, the cellulose-based hydrogels were obtained from the water hyacinth fibers (WHFs) with aids of borax as a chemical cross-linker. The chemical treatment on WHFs, confirmed by Fourier transform infrared (FT-IR) analysis and thermogravimetric analysis (TGA), exhibited the reduction of hemicellulose and lignin. The treated cellulose fibers were dissolved in the mixed solution of NaOH/urea prior to mixing with borax at the cellulose/borax weight ratio of 1/0, 1/0.5 and 1/1 to prepare cellulose-based hydrogels. The effect of borax contents on the properties of cellulose-based hydrogels was investigated. The results showed that the swelling ratio and equilibrium water content of the obtained hydrogels were similar with increasing a borax content.

This work aimed to study the extraction of nanocellulose (CNC) from pineapple leaves (PL) for using as a reinforcing filler in the natural rubber. PL mainly consists of cellulose so it is properly used for nanocellulosic extraction. The extractions were performed by acid-hydrolysis and pressurized acid-hydrolysis methods. The morphology and structure of the extracted nanocelluloses were compared and investigated using transmission electron microscope, Fourier transformed infrared, and X-ray diffraction analysis. It was found that pineapple leave has 27.64% of α-cellulose. The size of celluloses, which were extracted and hydrolyzed by acid-hydrolysis and pressurized acid hydrolysis, were reduced to 130 and 117 nm, respectively. And the shape was rodlike. The crystallinity index (CrI) of CNC was increased to 92.95 % and 91.24 % when it was treated by acid hydrolysis and pressurized acid hydrolysis, respectively.

The conductive paper has been of great interest due to its flexibility and superior properties. In this work, the facile procedure with scalable possibility was used to prepare conductive paper with graphene oxide (GO) and reduced graphene oxide (rGO). GO synthesized by the modified Hummers’ method was successfully transformed to rGO using ascorbic acid. These GO and rGO were used as a conductive source to improve conductive properties of the as-prepared paper. GO and rGO (0 – 25 wt%) were mixed with nanofibrillated cellulose (NFC) to form conductive paper. Results showed that the reduction of the electrical resistance was found from both GO/NFC and rGO/NFC paper sheets with increasing a content of GO or rGO. Furthermore, the paper with rGO exhibited more outstanding electrical conductive than the GO/NFC paper. Also, the water uptake of the conductive paper was affected by the addition of GO or rGO. The significant reduction of water uptake was found to be more pronounced with the introduction of rGO in comparison with the presence of GO. The conductive paper prepared in this study would be useful for applications such as flexible electrode.

In Thailand, pineapple leaves are one of the most common agricultural wastes after cultivation. The aim of this research was to understand effects of the steam explosion treatment conditions (steam pressure and treatment cycle) on properties of cellulose microfibers extracted from pineapple leaves. The fibers were steam exploded at pressure of 16 and 20 kgf cm−2 between 1 and 5 cycles. The steam explosion technique could partially eliminate hemicellulose and lignin and increase the cellulose content, leading to improvement of the thermal properties and crystallinity of the treated fibers. With increasing the steam pressure and treatment cycles, changes of the fiber morphology were observed. Smaller widths and shorter lengths of the treated fibers could be obtained. Microfibers with widths of 3 μm and lengths of 93 μm were extracted from fiber bundles with widths of 45.8 μm and lengths of ∼2 cm with the pressure of 20 kgf cm−2 for 5 cycles. Also, the steam explosion method could possibly fibrillate cellulose nanofibers. With more cycles of the steam explosion treatment, large amounts of cellulose nanofibers could be found.

Microfibrillated cellulose (MFC) was successfully prepared from lyocell fibers using combined homogenization and sonication treatments. MFC fibrils with a mean diameter of ~365 nm were observed, after the lyocell fibers with diameters of ~10 μm were mechanically treated for 60 min. Poly (vinyl alcohol) (PVA) composites reinforced with MFC were then fabricated using a solvent casting method. Physical and mechanical properties of the MFC reinforced PVA composites were investigated. An increase of ~13 and ~34 % of tensile strength and Youngs modulus was observed for the 3 wt% MFC reinforced composites, compared to those of the pure PVA. Raman spectroscopy was also employed to study the deformation micromechanics of the MFC reinforced PVA composites. The position of the Raman peak initially located at 1095 cm-1, corresponding to the C-O ring stretching and C-O-C glycosidic bond stretching modes, was recorded. During tensile deformation, this peak was observed to shift towards a lower wavenumber position, indicating stress-transfer between the resin and the fibrils.

Lyocell fibres were used to make microfibrillated cellulose (MFC) by combined homogenisation and sonication. A web-like structure was obtained with fibril diameters in the range of several micrometers to less than 80 nm. Composite samples with PLA resin reinforced with MFC networks were prepared using compression moulding. Young's modulus and tensile strength of these composites increased by similar to 60% and 14% respectively, compared to the pure resin material. Raman spectroscopy was used to monitor the molecular deformation of networks and composite materials. A Raman band initially located at similar to 1095 cm(-1) was observed to shift towards a lower wavenumber position upon tensile deformation. The rate of Raman band shift with respect to strain for the composites was higher than for the pure MFC networks, indicating that the observed improvement in mechanical properties results from stress transfer from the PLA resin to the MFC fibrils.

Polymer blends between pristine polypropylene (PP) and post-consumer soft-drink PET bottles (rPET) were prepared using pulverization technique. The polymer mixtures were pulverized, at the amounts of rPET in PP of 0, 10, 15, 20 and 30 phr (parts per hundred of resin) by weight, into powder. In an extruder, the polymer powders were mixed with maleic anhydride-grafted polypropylene (MAPP) and polyethylene wax (PE wax) as a compatibilizer and a processing aid, respectively. The extrudates were prepared into test specimens by injection molding. Physical properties of PP/rPET blends were subsequently investigated. The results pointed out that, for the pulverized blends without compatibilizer, tensile and flexural strength were improved at the lower amount of rPET. The compatibilizing effect of MAPP was exhibited at the higher amount of rPET. The reduction of melt flow index (MFI) may cause difficulties for some processing techniques which required polymers with high MFI. The addition of PE wax successfully brought up the MFI as well as elongation at break while other mechanical properties decreased.

In this research, reactive blending of thermoplastic polyurethane (TPU) and polypropylene (PP) was studied. Grafting of maleic anhydride (MAH) onto TPU/PP blends was performed by a twin-screw extruder in the presence of dicumyl peroxide (DCP). Mechanical properties and morphology of the blends were investigated by tensile testing and scanning electron microscopy (SEM), respectively. Thermal properties of the blends were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The obtained results were compared with those of the uncompatibilized blends and the blends compatibilized with a commercial maleic anhydride grafted polypropylene (PP-g-MA). The results from the uncompatibilized blends clearly indicate that the TPU and PP are immiscible resulting in undesirable properties of the blends. These properties were improved significantly when TPU and PP were reactive-blended in the presence of MAH and DCP. When comparing with the blends compatibilized with PP-g-MA, the blends prepared by the reactive blending technique possessed better mechanical properties.

This work concerns a study on the effects of fiber types and content of cellulose nanofiber on mechanical, thermal, and optical properties polyvinyl alcohol (PVA) composites. Two different types of cellulose nanofibers, which are nanofibrillated cellulose (NFC) and bacterial cellulose (BC), were prepared under various mechanical treatment times and then incorporated into the PVA prior to the fabrication of composite films. It was found that tensile modulus of the PVA film increased with nanofibers content at the expense of its percentage elongation value. DSC thermograms indicate that percentage crystallinity of PVA increased after adding 2–4 wt% of the fibers. This contributed to the better mechanical properties of the composites. Tensile toughness values of the PVA/BC nanocomposite films were also superior to those of the PVA/NFC system containing the same fiber loading. SEM images of the composite films reveal that tensile fractured surface of PVA/BC experienced more ductile deformation than the PVA/NFC analogue. The above discrepancies were discussed in the light of differences between the two types of fibers in terms of diameter and their intrinsic properties. Lastly, percentage total visible light transmittance values of the PVA composite films were greater than 90%, regardless of the fiber type and content.

In this work, poly(vinyl alcohol) (PVA) and cellulose nanocrystals (CNCs) were crosslinked using sodium tetraborate decahydrate (borax) to improve the mechanical and thermal properties of the neat PVA. The results showed that the CNCs affected the crystallization behavior of the crosslinked PVA. The crystallization temperature of the crosslinked PVA with CNCs increased considerably from ∼152 to ∼187 °C. The continuous improvement of the thermal stability was observed with the increasing content of CNCs in the crosslinked PVA films. Additionally, the strong interaction between the CNCs and PVA was theoretically estimated from the Young's modulus values of the composites. Thermodynamic mechanical testing revealed that the crosslinked PVA composite films with CNCs could bear higher loads at high temperature compared to the films without the CNCs. At 60 °C, 2.7 GPa was reported for the storage modulus of the crosslinked composites with 3 wt % of CNCs, twice as high as that for the crosslinked films without CNCs. Moreover, creep results were improved when CNCs were added in the crosslinked nanocomposites. The materials prepared in this work could broaden the opportunities for applications in a wide range of temperatures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45710.

This research work aims to investigate the effects of types and concentration of cellulose nanocrystals (CNCs) prepared from bacterial cellulose (BC) and nanofibrillated cellulose (NFC) on structur ...

2, 24, Journal of Metals, Materials and Minerals

The deformation micromechanics of bacterial cellulose (BC) and microfibrillated cellulose (MFC) networks have been investigated using Raman spectroscopy. The Raman spectra of both BC and MFC networks exhibit a band initially located at ≈ 1095 cm(-1). We have used the intensity of this band as a function of rotation angle of the specimens to study the cellulose fibril orientation in BC and MFC networks. We have also used the change in this peak's wavenumber position with applied tensile deformation to probe the stress-transfer behavior of these cellulosic materials. The intensity of this Raman band did not change significantly with rotation angle, indicating an in-plane 2D network of fibrils with uniform random orientation; conversely, a highly oriented flax fiber exhibited a marked change in intensity with rotation angle. Experimental data and theoretical analysis shows that the Raman band shift rate arising from deformation of networks under tension is dependent on the angles between the axis of fibrils, the strain axis, the incident laser polarization direction, and the back scattered polarization configurations. From this analysis, the effective moduli of single fibrils of BC and MFC in the networks were estimated to be in the ranges of 79-88 and 29-36 GPa, respectively. It is shown also that for the model to fit the data it is necessary to use a negative Poisson's ratio for MFC networks and BC networks. Discussion of this in-plane "auxetic" behavior is given.

Composites of poly(lactic) acid (PLA) reinforced with TEMPO-oxidized fibrillated cellulose (TOFC) were prepared to 15, 20, 25, and 30% fiber weight fractions. To aid dispersion and to improve stress transfer, we acetylated the TOFC prior to the fabrication of TOFC-PLA composite films. Raman spectroscopy was employed to study the deformation micromechanics in these systems. Microtensile specimens were prepared from the films and deformed in tension with Raman spectra being collected simultaneously during deformation. A shift in a Raman peak initially located at ~1095 cm(-1), assigned to C-O-C stretching of the cellulose backbone, was observed upon deformation, indicating stress transfer from the matrix to the TOFC reinforcement. The highest band shift rate, with respect to strain, was observed in composites having a 30% weight fraction of TOFC. These composites also displayed a significantly higher strain to failure compared to pure acetylated TOFC film, and to the composites having lower weight fractions of TOFC. The stress-transfer processes that occur in microfibrillated cellulose composites are discussed with reference to the micromechanical data presented. It is shown that these TOFC-based composite materials are progressively dominated by the mechanics of the networks, and a shear-lag type stress transfer between fibers.