The emphasis of this study have been to study if impregnation of cellulose nanofibre networks can be made using a thermoplastic polymer as a matrix and to estimate the reinforcing efficiency of the cellulose nanofibres in this composite. A nanofibre network with higher porosity that water-dried nanofibre network was prepared from a cellulose waste byproduct (sludge). This was impregnated using a diluted solution of cellulose acetate butyrate polymer to produce a 60 wt. % CNF/CAB composite. This composite was characterized using microscopy and mechanical testing. High porosity is seen in the SEM images of the acetone-dried fibre network and SEM and film transparency was used to qualitatively assess the impregnation of the network. A significant improvement in the visible light transmittance was observed for the nanocomposite film compared to the nanofibre network as a result of the impregnation. The reinforcing efficiency was calculated based on a model of the nanocomposite and compared to other nanocomposites in the literature. The efficiency factor takes into account the volume fraction and the stiffness of the matrix. This showed that this CNF/CAB combination is similar in efficiency to CNF/PLA nanocomposites and more efficient that nanocomposites using when using stiffer matrices. It was also more efficient CNF nanocomposites based on Chitosan, which has the same stiffness. It is still however not as efficient as traditional glass polymer composites due to the random orientation of the fibres nor nanocomposites with very soft matrices due to the dominating network effect of the CNF in such composites. In conclusion, CAB impregnated cellulose nanofibre networks are promising biocomposite materials that could be used in applications where transparency and good mechanical properties are of interest. The key elements in the impregnation process of the nanocomposites were the use of a porous networks and a low viscosity thermoplastic resin solution.

In this work, three-dimensional (3D) aerogels and hydrogels based on lignin-containing arabinoxylan (AX) and cellulose nanofibers (CNF) were prepared. The effects of the CNF and the crosslinking with citric acid (CA) of various contents (1, 3, 5 wt%) were evaluated. All the aerogels possessed highly porous (above 98%) and lightweight structures. The AX-CNF hydrogel with a CA content of 1 wt% revealed a favorable network structure with respect to the swelling ratio; nanofiber addition resulted in a five-fold increase in the degree of swelling (68 g of water per g). The compressive properties were improved when the higher CA content (5 wt%) was used; when combined with CNF, there was a seven-fold enhancement in the compressive strength. The AX-CNF hydrogels were prepared using a green and straightforward method that utilizes sustainable resources efficiently. Therefore, such natural hydrogels could find application potential, for example in the field of soft tissue engineering.

Application of natural fibre composites is going to increase in different areas caused by environmental, technical and economic advantages. However, their low mechanical properties have limited their particular application in automotive structural components. Hybridizations with other reinforcements or matrices can improve mechanical properties of natural fibre composite. Moreover, geometric optimizations have a significant role in structural strength improvement. This study focused on selecting the best geometrical bumper beam concept to fulfill the safety parameters of the defined product design specification (PDS). The mechanical properties of developed hybrid composite material were considered in different bumper beam concepts with the same frontal curvature, thickness, and overall dimensions. The low-speed impact test was simulated under the same conditions in Abaqus V16R9 software. Six weighted criteria, which were deflection, strain energy, mass, cost, easy manufacturing, and the rib possibility were analyzed to form an evaluation matrix. Topsis method was employed to select the best concept. It is concluded that double hat profile (DHP) with defined material model can be used for bumper beam of a small car. In addition, selected concept can be strengthened by adding reinforced ribs or increasing the thickness of the bumper beam to comply with the defined PDS.

Environmental regulations, costs and lightweight encourage car manufacturers to develop new reliable products. Epoxy provides a reliable fibre impregnation and creates substantial three-dimensional (3D) cross-linking for proper load transmission and impact strength improvement, but their low toughness decreases their energy absorption. Thermoplastic toughening improves the epoxy impact property with a low thermo-mechanical defect. This study, focused on improving the impact property of hybrid kenaf/glass fibre epoxy composite by use of a modified sheet moulding compound (GMT). The results indicated that most of the mechanical properties of developed material were almost the same as those of the GMT, except impact. This result highlights the potential for utilisation of the toughened hybrid bio-composite in some automotive structural components. Moreover, geometric parameters, e.g., cross-section, thickness, and reinforcement ribs suggest an improvement of structural impact resistance to comply with the bumper beam product design specification (PDS).

In this study, two types of new bioadhesives formulated from abundant and renewable soybean flour (SF), acetylated soybean flour based adhesive (ASF), and soybean flour-based adhesive, were modified with acetylated cellulose nanocrystal (ACNC). The apparent viscosity and morphology of the adhesive formulations were characterized. The chemical composition of the formulations was evaluated by FT-IR spectroscopy and the effect of polyethilenimine (PEI) on the formulations was investigated using the proton nuclear magnetic resonance (¹H NMR) spectra. Moreover, water resistance of produced plywood composites bonded with the bioadhesives was measured. The results of FT-IR and ¹H NMR confirmed that chemical modifications of the SF occurred. The scanning electron microscopy (SEM) images showed less holes and cracks on the cross section of the ASF/PEI/NaOH and SF/PEI/NaOH/ACNC formulations. The results showed that the plywood specimens bonded with formulations of the ASF/PEI/NaOH (with a dry weight ratio of ASF/PEI: 5/1 and 6/1), and SF/PEI/NaOH/ACNC had good resistance to water. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Biobased nanocomposite sheets of cellulose nanofibres (CNF) and cellulose acetate butyrate (CAB) were prepared using a resin impregnation technique. Porous nanofibre networks together with a low viscosity thermoplastic resin were the key elements in the processing. SEM images of the network before the impregnation showed high porosity and after the impregnation indicated impregnated fibre network. A significant improvement in the visible light transmittance was observed for the nanocomposite compared to the nanofibre network, which is explained on the filling of the pores with a transparent matrix. The tensile tests showed an increase of 364% and 145% for stiffness and strength respectively for nanocomposites with 60 wt.% CNF when compared to CAB. Dynamic mechanical properties showed a good interaction between the CAB and cellulose nanofibres. These results show that CAB impregnated cellulose nanofibre networks are promising biocomposite that could be used in applications where transparency and good mechanical properties are of interest.

Surface modification of mixed hardwoods fibers by sodium hydroxide (NaOH) was conducted to investigate the effect of chemical treatment on the fiber properties along with physico-mechanical characteristics of the medium density fiberboard (MDF). The results indicated that the NaOH treatments can dissolve a portion of hemicelluloses and almost all amount of extractives from the fibers, but it was not strong enough to remove the lignin thoroughly. The FTIR results illustrated that chemical changes can occur during the various NaOH treatments of the fibers. X-ray diffraction analysis revealed that the crystallinity of the studied fibers increased after the alkaline treatment. Investigation of mechanical properties of the MDF showed that modulus of rupture and internal bond strength of the treated samples were decreased compared to the control ones. In addition, water absorption and thickness swelling of treated boards were higher than that of untreated samples. This study indicated that the physico-mechanical properties of the boards were negatively affected by the NaOH treatment.

The aim of this study was to develop cellulose nanofibers with hydrophobic surface characteristics using chemical modification. Kenaf fibers were modified using acetic anhydride and cellulose nanofibers were isolated from the acetylated kenaf using mechanical isolation methods. Fourier transform infrared spectroscopy (FTIR) indicated acetylation of the hydroxyl groups of cellulose. The study of the dispersion demonstrated that acetylated cellulose nanofibers formed stable, well-dispersed suspensions in both acetone and ethanol. The contact angle measurements showed that the surface characteristics of nanofibers were changed from hydrophilic to more hydrophobic when acetylated. The microscopy study showed that the acetylation caused a swelling of the kenaf fiber cell wall and that the diameters of isolated nanofibers were between 5 and 50 nm. X-ray analysis showed that the acetylation process reduced the crystallinity of the fibers, whereas mechanical isolation increased it. The method used provides a novel processing route for producing cellulose nanofibers with hydrophobic surfaces.

The aim of this study was to develop cellulose nanofiber (CNF) reinforced polylactic acid (PLA) by twin screw extrusion. Nanocomposites were prepared by premixing a master batch with high concentration of CNFs in PLA and diluting to final concentrations (1, 3, 5 wt%) during the extrusion. Morphology, mechanical and dynamic mechanical properties (DMA) were studied theoretically and experimentally to see how different CNF concentrations affected the composites' properties. The tensile modulus and strength increased from 2.9 GPa to 3.6 GPa and from 58 MPa to 71 MPa, respectively, for nanocomposites with 5 wt% CNF. The DMA results were also positive; the storage modulus increased for all nanocomposites compared to PLA; being more significant in the high temperature region (70°C). The addition of nanofibers shifted the tan delta peak towards higher temperatures. The tan delta peak of the PLA shifted from 70°C to 76°C for composites with 5 wt% CNF.

Kenaf (Hibiscus cannabinus) nanofibers were isolated from unbleached and bleached pulp by a combination of chemical and mechanical treatments. The chemical methods were based on NaOH-AQ (anthraquinone) and three-stage bleaching (DEpD) processes, whereas the mechanical techniques involved refining, cryo-crushing, and high-pressure homogenization. The size and morphology of the obtained fibers were characterized by environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM), and the studies showed that the isolated nanofibers from unbleached and bleached pulp had diameters between 10-90 nm, while their length was in the micrometer range. Fourier transform infrared (FTIR) spectroscopy demonstrated that the content of lignin and hemicellulose decreased in the pulping process and that lignin was almost completely removed during bleaching. Moreover, thermogravimetric analysis (TGA) indicated that both pulp types as well as the nanofibers displayed a superior thermal stability as compared to the raw kenaf. Finally, X-ray analyses showed that the chemo-mechanical treatments altered the crystallinity of the pulp and the nanofibers: the bleached pulp had a higher crystallinity than its unbleached counterpart, and the bleached nanofibers presented the highest crystallinity of all the investigated materials.

In the present study, chemical-physical properties of nanofibers isolated from rubberwood (Hevea brasiliensis) and empty fruit bunches (EFB) of oil palm (Elaeis guineensis) were analyzed by microscopic, spectroscopic, thermal and X-ray diffraction methods. The isolation was achieved using chemo-mechanical processes. Microscopy study showed that the diameters of the nanofibers isolated from the EFB ranged from 5 to 40 nm while those of the nanofibers isolated from rubberwood had a wider range (10-90 nm). Fourier transform infrared spectroscopy study demonstrated that almost all the lignin and most of the hemicellulose were removed during the chemical treatments. X-ray diffraction analysis revealed that the crystallinity of the studied nanofibers increased after the chemo-mechanical isolation process. The results of thermogravimetric analysis showed that the nanofibers isolated from both sources had higher thermal stability than those of the bleached pulp and untreated fibers

The goal of this work was to evaluate the effect of chemical modification of cellulose nanofibers (CNF) on the properties of polylactic acid (PLA) nanocomposites. Acetylated nanofibers (ACNF), with degree of substitution 1.07, were isolated from acetylated kenaf fibers by mechanical treatments. Acetylated nanofibers showed more hydrophobic properties compared to non-acetylated ones. The results showed that both crystallinity and thermal stability of acetylated nanofibers were lower than non-acetylated ones. The nanocomposites were prepared by premixing two PLA master batches, one with a high concentration of ACNF and the second with CNF. These were diluted to final concentrations (5 wt%) during the extrusion. The morphology studies of PLA and its nanocomposites showed nanofiber aggregates in both materials. The results showed that the tensile and dynamic mechanical properties were enhanced for both acetylated and non-acetylated nanocomposites compared to the neat PLA matrix while no significant improvement was observed for the acetylated nanocomposites compared to non-acetylated ones. However, the storage modulus increased slightly for acetylated nanocomposites compared to non-acetylated ones.

The aim of this study was to isolate cellulose nanofibers by ultrafine grinding, from sludge (residue from dissolving cellulose production) and cellulose (dissolving cellulose) and to characterize their properties. The mechanical fibrillation was found to be more energy efficient at low rotor speed (1440) and was estimated to be 1.7 and 1.3 kWh/kg for cellulose (CF) and sludge fibers (SF), respectively. Sludge (SNF) and cellulose (CNF) nanofibers had diameter less than 100 nm, as measured from transmission electron microscopy images. The specific surface area ranged from approximately 84 to 112 m2/g for CNF and SNF respectively. The apparent networks density increased with fibrillation, being approximately 330 and 370 for CF and SF while 907 and 986 kg/m3 for the corresponding nanosized ones. The scanning electron microscopy (SEM) study exhibited considerably smoother surfaces for the nanofiber networks compared to microsized. Fibrillation to nanosized fibers had positive impact on modulus and strength of both raw materials and the improvement was more significant for sludge, indicating more efficient fibrillation. The study showed that the isolation of nanofibers from sludge could be considered an economic, energy efficient and viable alternative to generate value-added product from cellulose sludge while minimizing the sludge disposal issues.

The removal of di(2-ethylhexyl)phthalate (DEHP) from aqueous solutions by cellulose nanofibers (CNFs), derived from softwood, was studied. The optimum conditions of four factors at four levels including the DEHP concentration (1–10 mg/L), adsorbent dose (0.5–3 g/L), contact time (30–180 min), and pH (3–9) in a batch system was investigated by the design of experiment software. The Isotherm Fitting Tool software was used to fit isotherm parameters to experimental data. The maximum removal efficiency, (74.1%), was obtained at a DEHP concentration of 10 mg/L, an adsorbent dose of 0.5 g/L, a contact time of 30 min, and a pH of 7. The amount of DEHP adsorbed per unit weight of adsorbent (q_e) in the optimum conditions was 14.8 mg/g. The system was well corresponded by the generalized Langmuir–Freundlich model. The results showed that extracted CNF from softwood has a good potential for treatment of polluted aqueous solutions by DEHP.

The aim of this study was to explore the utilization of industrial bio-residues as a source of raw material for the industrial production of cellulose nanowhiskers. The used residue, obtained from a bioethanol pilot plant, was first purified using chemical extraction and bleaching, and then separated to nanowhiskers by mechanical treatments such as ultrasonication, high-pressure homogenization as well as chemical acid hydrolysis.The chemical compositions and characteristics of the bio-residue were studied before and after purification using a TAPPI standard, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphology of the isolated nanowhiskers was characterized using atomic force microscope (AFM). The chemical composition of the used bio-residue was found to be 49.5 wt% cellulose, 42.1 wt% lignin and 8.4 wt% extractives. The crystallinity of the bio-residue was 14.5% and it increased to more than 73% after the purification process. The nanowhiskers isolated using ultrasonication or high-pressure homogenization had better thermal stability than nanowhiskers isolated with acid hydrolysis. The AFM study showed that a simple ultrasonication and homogenization processes resulted in nanosize whiskers with diameters in the 10-20 nm range.

We have been working with development of compounding extrusion process for cellulose nanocomposites, since 2003. Feeding and dispersion of the nanocellulose materials are the main challenges and we have developed two specific processing routes; i) liquid feeding of the nanomaterials into the extruder and ii) dry feeding of nanomaterials as a master batch, to address the feeding problem. Composites with aggregated, partially dispersed or fully dispersed nanocellulose crystals or fibers have been obtained depending on the extent of the separation of cellulose nanocrystals or nanofibers in the liquid medium or in the master batch and the interaction of nanocelluloses with the polymer matrix. We aim to produce nanocomposites with good mechanical properties, thermal stability and transparency and at the same time develop an energy efficient and cost effective processing methodology, which can be up-scaled in industrial level.

Isolation of cellulose nanofibers from industrial side-streams as raw material is interesting from several reasons; it will not only result in lower overall cost of the nanofibers but also add value for many different processes and products. We have used sludge, a residue from pulp production, carrot residue from juice production, and several agricultural waste products as the starting material to isolate nanofibers. The isolation process was made using a Masuko ultra fine friction grinder and our aim have been to optimize the processing parameters for the lowest energy consumption. In addition to developing the isolation process, the isolated nanofibers structure and properties were characterized. Typically, the isolated nanofibers are bundles with diameters lower than 100 nm. In particular, we found that carrot nanofibers have a uniform fiber size less than 50 nm. Scanning electron microscopy studies showed entangled nanofiber networks and the mechanical properties of nanofiber networks demonstrated a positive impact on modulus and strength when compared to networks with microsized fibers. The improvement is increased with decreased fiber size indicating more efficient fibrillation. From these studies, we have shown that industrial side-streams are excellent raw material sources for nanofiber preparation, being cheaper than other raw materials and consuming less energy for isolation while showing good properties.

The main aim of this study was to develop a novel approach to incorporate high cellulose nanofiber (CNF) loadings into polyvinyl alcohol (PVA) nanocomposites. The nanocomposites were prepared by freezing via liquid nitrogen and consequent freeze drying combined with hot press molding. To investigate the effect of the molding parameters on the morphological, mechanical and thermal properties, chemical structure and transparency of the PVA + CNF nanocomposites, two different mold pressures, temperatures and holding times were used for fabrication of PVA + CNF nanocomposites. The maximum tensile strength of 121 MPa of the PVA + CNF 20% nanocomposites was obtained when they were molded at 130 °C and 50 kPa for 7 min. Dynamic mechanical analysis showed that the storage modulus of the composites prepared at 130 °C and 50 kPa for 7 min is about 20% higher than nanocomposites molded at 150 °C and 150 kPa for 10 min. Optical properties (absorption spectra) of the PVA and PVA + CNF nanocomposites were increased as the mold pressures, temperature and holding time increased. Micrographs showed more sough fracture surface with increasing pressure and temperature during hot press molding.

Kenaf nanofibers (NF) were isolated from the kenaf pulp using mechanical isolation methods (refining with super grounding and high pressure homogenization). The kenaf NF were acetylated to produce hydrophobic NF. FTIR results displayed a successful acetylation of the NF. X-ray analysis exhibited that the acetylation process reduced the crystallinity of kenaf NF but also that isolation to NF leads to higher crystallinity than corresponding micro-sized fibers. The contact angle measurements indicated that the acetylation treatment changed the surface characteristics of the kenaf NF from hydrophilic to more hydrophobic.

A fundamental understanding of the relationships between basic fiber properties, methods of processing, and composite end use performance properties has been well developed due to recent advances within the biocomposites research community. Simultaneously, advanced engineered biocomposites are currently being developed to meet the diverse needs of users for high-performance materials as well as economical commodity products. Advancements in nanotechnology have led to industrial isolation of nanocrystalline cellulose [1, 2]. While nanocrystalline cellulose may be only 1/10 as strong as carbon nanotubes – currently the strongest known structural material [3, 4] – it may cost 50–1,000 times less to produce [5, 6]. Engineered biocomposites employing nanocrystalline cellulose reinforcement could soon provide advanced performance, durability, value, service life, and utility, while at the same time being a fully sustainable technology.