Eucalyptus Fibers Research Articles

The role of lignin in polypropylene composites with semi-bleached cellulose fibers: Mechanical properties and its activity as antioxidant

Reports on the use of bleached Eucalyptus cellulose as a reinforcing agent for polypropylene and on the use of lignin, from Eucalyptus and other vegetal species, as a stabilizer for different polymers can be found in the scientific literature. This work focuses on polypropylene composites using cellulose fibers with different bleaching levels, i.e. containing controlled lignin contents. We compared the properties and stability of composites with bleached and with semi-bleached fibers. These were prepared by twin-screw extrusion and injection molding and characterized by their tensile and flexural mechanical properties, thermogravimetry, oxidation induction time, reflectance infrared spectrophotometry and scanning electron microscopy. The kinetic evaluation of the accelerated and environmental aging of the injection molded test samples was followed by mechanical properties variation and reflectance infrared spectrophotometry. An increase in the reinforcing effect of the fibers and on the stability of the composites was observed for composites containing semi-bleached Eucalyptus fibers, with different lignin contents, compared to composites with the bleached cellulose fibers. The lignin present in these semi-bleached fibers positively affected the mechanical properties of the composites and the hindered phenols in the lignin structure acted as a primary anti-oxidant, indicating their advantageous use in comparison to the bleached fibers. Scanning electron micrographs showed that the excellent bulk fiber/matrix adhesion was not affected by accelerated or environmental aging.

Structural characterization of residual hemicelluloses from hydrothermal pretreated Eucalyptus fiber

In this study, an environmental-friendly hydrothermal pretreatment of Eucalyptus fiber followed with alkali post-treatment was developed to produce bioethanol efficiently. This biorefinery process allowed all major components of biomass being converted into high value-added products. The chemical and structural features of the residual hemicelluloses isolated with alkali from the hydrothermal pretreated Eucalyptus fiber, were comparatively investigated. Sugar and spectral analyses indicated that the hemicelluloses were mainly composed of glucuronoxylans, and especially hemicelluloses prepared at higher temperature (180°C) contained higher contents of glucomannans and α-glucan. Hydrothermal pretreatment resulted in a significant hydrolysis of the glycosidic linkages in xylan backbone, and thus the molecular weight of the hemicelluloses was significantly reduced from 56,520 to 7780g/mol with the increase of temperature. This suggested that a combination of hydrothermal pretreatment at low temperatures (100–140°C) and alkali post-treatment was an effective technique for isolating of hemicelluloses from Eucalyptus fiber.

Bioensaios em painéis confeccionados com eucalipto e bagaço de cana-de-açúcar

No desenvolvimento de painéis, deve-se dar destaque a ensaios que remetam à aplicabilidade final do produto, como os ensaios de durabilidade ao ataque de fungos e cupins. Nesse contexto, painéis confeccionados com diferentes percentuais de partículas de bagaço de cana-de-açúcar (Saccharum sp.) e fibras de eucalipto (Eucalyptus grandis), aglutinados com duas dosagens de resina ureia formol (13% e 16%), foram submetidos à avaliação de resistência biológica (bioensaios) ao ataque de cupins e fungos, ensaio fundamental na definição de uso e aplicação do produto final. Foram utilizados cupins da espécie Reticulitermes santonensis, rhinotermitidade, e fungos da espécie Pleurotus ostreatus, basidiomiceto de podridão-branca, de acordo com procedimentos da normatização AFNOR. De modo geral, os novos painéis confeccionados apresentaram-se não resistentes aos bioensaios realizados e houve similaridade na dinâmica de ataque e perda de massa entre as diferentes dosagens de resina praticadas, remetendo à necessidade da aplicação de revestimento protetor na superfície dos painéis ou adição de produtos fungicidas e cupinicidas.

Influence of coupling agent in compatibility of post-consumer HDPE in thermoplastic composites reinforced with eucalyptus fiber

This study investigates the feasibility of using recycled high density polyethylene (HDPE) and wood fiber from species Eucalyptus grandis (EU) to manufacture experimental composite panels. The use of maleated polyethylene as coupling agent (CA) improved the compatibility between the fiber and plastic matrix. The mechanical properties of the resultant composites were compared with polymer with and without compatibilizer. The influence of the coupling agent (CA) in the polymer matrices and composites were evaluated at different concentrations, checking the physical, mechanical and thermal properties of wood plastic composites (WPC). Results of mechanical, physical and thermal properties showed that concentration of 3% w/w CA in the polymer matrices was that which showed the best results, but in the composites properties were very similar in all formulations. Based on the findings in this work, it appears that recycled materials can be used to manufacture value-added panels without having any significant adverse influence on material properties.

Improving the enzymatic hydrolysis of thermo-mechanical fiber from

The recalcitrance of lignocellulosic biomass is a major limitation for its conversion into biofuels by enzymatic hydrolysis. The use of a pretreatment technology is an essential step to diminish biomass recalcitrance for bioethanol production. In this study, a two-step pretreatment using hydrothermal pretreatment at various temperatures and alkali fractionation was performed on eucalyptus fiber. The detailed chemical composition, physicochemical characteristics, and morphology of the pretreated fibers in each of the fractions were evaluated to advance the performance of eucalyptus fiber in enzymatic digestibility. The hydrothermal pretreatment (100 to 220°C) significantly degraded hemicelluloses, resulting in an increased crystallinity of the pretreated fibers. However, as the pretreatment temperature reached 240°C, partial cellulose was degraded, resulting in a reduced crystallinity of cellulose. As compared to the hydrothermal pretreatment alone, a combination of hydrothermal and alkali treatments significantly removed hemicelluloses and lignin, resulting in an improved enzymatic hydrolysis of the cellulose-rich fractions. As compared with the raw fiber, the enzymatic hydrolysis rate increased 1.1 to 8.5 times as the hydrothermal pretreatment temperature increased from 100 to 240°C. Interestingly, after a combination of hydrothermal pretreatment and alkali fractionation, the enzymatic hydrolysis rate increased 3.7 to 9.2 times. Taking into consideration the consumption of energy and the production of xylo-oligosaccharides and lignin, an optimum pretreatment condition was found to be hydrothermal pretreatment at 180°C for 30 min and alkali fractionation with 2% NaOH at 90°C for 2.5 h, in which 66.3% cellulose was converted into glucose by enzymatic hydrolysis. The combination of hydrothermal pretreatment and alkali fractionation was a promising method to remove hemicelluloses and lignin as well as overcome the biomass recalcitrance for enzymatic hydrolysis from eucalyptus fiber. In addition, the various techniques applied in this work constituted an efficient approach to understand the underlying chemical and morphological changes of the cellulose-rich fractions.

Effect of process variables on quality improvement of TGW pulps of Eucalyptus

High-yield pulps are usually derived from pine wood on account of its anatomical configuration and technology used. Eucalyptus, on the other hand, is a fast-growing species, abundant in many parts of the world, and has thus emerged as an alternative source for many products in the pulp and paper industry. In this particular study, high-yield pulps of Eucalyptus grandis were used. In order to improve their properties, pulps were subjected to chemical treatments with different doses of sodium hydroxide prior to refining (0, 30, 50 and 70 kg/t), at 75ºC temperature, 3% consistency, during 1 minute. The refining process was done in a Bauer disc refiner (Regmed) using various refining times (0, 5, 10 and 15 minutes). Results showed that refining with addition of NaOH did bring significant gains to the eucalyptus fibers regarding strength properties, the dose 50 kg/t being found the most suitable. However, other variables associated with refining could also be modified to further improve the strength properties of eucalyptus pulps, including consistency and refining discs configuration.

Density profile as a tool in assessing quality of new composite

This paper present a study to apply the X-ray densitometry technique in obtaining density profiles, along the thickness of new composites made from eucalyptus fibers and sugarcane bagasse particles. Experimental panels were made in treatments with different percentages of both raw materials and bonded with two urea formaldehyde resin percentages, 13% and 16%, with target density of 750 kg m-3, obtaining density profiles and qualitative variables of maximum, medium and minimum densities. The results indicated that the dosage of resin at 16% promoted greater homogeneity in the profile formats and statistical similarity between the minimum density values in the different treatments, which refers to performance as to the internal bond. The density profiles along the thickness showed variations of the panel frame and provided important quality information, applied to the press cycle setting and indications of its technological performance, expanding the possibilities of raw material parameter diagnosis and the panel manufacturing processes.

All-cellulose composites from unbleached hardwood kraft pulp reinforced with nanofibrillated cellulose

In the present work, nanofibrillated cellulose (NFC) from bleached eucalyptus pulp was prepared, characterized and used as reinforcement in an unbleached eucalyptus fiber matrix. First, the NFC was fabricated through TEMPO-mediated oxidation and characterized for the degree of polymerization, water retention value, cationic demand and carboxyl content. Intrinsic mechanical properties were also calculated by applying the rule of mixtures, which determines the coupling (f c) and efficiency factor (η e) of cellulose nanofibrils within the matrix. The results showed that the average intrinsic tensile strength and Young’s modulus of NFC are estimated to be 6,919 MPa and 161 GPa, respectively. After characterization, the NFC was used as reinforcement in the preparation of biocomposites in the form of paper handsheets, which were physically and mechanically analyzed. The presence of NFC induced an increase in the density of biocomposites and significant enhancement of the mechanical properties as well as an important reduction in porosity. Finally, f c and η e were determined from the mean intrinsic properties.

Key role of the hemicellulose content and the cell morphology on the nanofibrillation effectiveness of cellulose pulps

The effect of the hemicellulose content and that of the fibre morphology on the nanofibrillation behaviour of delignified cellulose pulps were studied. For this purpose, pulps from two non-woody plants, alfa (Stipa tenacissima) and sunflower (Helianthus annuus), were delignified using NaClO2/acetic acid and the NaOH pulping processes to obtain fibres with different hemicellulose contents. The ensuing fibres were characterized by chemical analysis, SEM, FTIRS and X-ray diffraction. The fibres were then disintegrated into nanofibrillated cellulose (NFC) using either a high pressure homogenizer or a domestic blender. The degree of fibrillation and the morphology of the nanofibrillated fractions were evaluated by centrifugation and Field-emission scanning electron microscopy. Pulps containing the highest hemicellulose content showed higher yields of the nanofibrillated fraction and a better aptitude for the individualization of the microfibrils. Furthermore, it was shown that fibres from sunflowers exhibiting a thinner cell wall were easier to fibrillate and could be disintegrated into NFC by just using a simple domestic-blender once deliginification process was carried out using the NaClO2/acetic acid method. Eucalyptus fibres were also used to further confirm the key role of hemicelluloses in the nanofibrillation process of woody plants.

Enzymatic strategies to improve removal of hexenuronic acids and lignin from cellulosic fibers

Abstract Different enzymatic strategies were applied to improve lignin and hexenuronic acid (HexA) removal. Three laccases (L) with different redox potentials were applied in combination with 1-hydroxybenzotriazole or methyl syringate to softwood sulfite and hardwood kraft fibers. The enzymes with a high-redox potential from Pycnoporus cinnabarinus and Trametes villosa were found to be the most efficient. The bleaching efficiency was not significantly influenced by the presence or absence of HexA in the different types of lignocellulosic fibers. Subsequently, the lignin or HexA removal in the presence of different mediators was evaluated in eucalyptus fibers with the T. villosa laccase (TvL). Natural mediators removed only lignin, whereas the combinations of TvL with synthetic mediators removed both HexA and lignin. The mediator violuric acid (VA) was the most efficient as judged by the properties of fiber and effluent. A xylanase pretreatment stage was found to boost the access of the LVA system to HexA without affecting lignin in the pulp.

Effectiveness of novel xylanases belonging to different GH families on lignin and hexenuronic acids removal from specialty sisal fibres

AbstractBACKGROUNDThe effectiveness of xylanases on lignin removal from pulps differs widely depending on the enzyme family, the type of pulp and the bleaching sequence among other factors. Xylanases can also reduce the presence of undesirable hexenuronic acids in the papermaking fibers. The performance of non‐commercial xylanases belonging to families GH10, GH30, GH30‐CBM35 and GH11, and of the multicomponent xylanase from Paenibacillus barcinonensis for lignin and hexenuronic acids removal from sisal (Agave sisalana) has been evaluated.RESULTSSisal pulps were bleached by an XP sequence, where X denotes the enzyme treatment and P a hydrogen peroxide extraction stage. Kappa number, brightness, viscosity and hexenuronic acid content of samples were determined. Sugars released from sisal pulps, other non‐wood fibres and also eucalyptus fibres, by the treatment with xylanases were also analysed. The best results were obtained with the GH10 xylanase and with crude supernatants of P. barcinonensis, which produced a lignin removal of 23% and a reduction of 25% in the hexenuronic acid content of sisal pulps without a significant loss of viscosity.CONCLUSIONThe release of sugars in the effluents from the X stage applied to sisal correlated with the effectiveness of the xylanases tested. The xylan content of wood and non‐wood fibres, the type of xylan and its accessibility also had an influence on the xylanase activity on pulps. © 2013 Society of Chemical Industry

Mapping the lignin distribution in pretreated sugarcane bagasse by confocal and fluorescence lifetime imaging microscopy

BackgroundDelignification pretreatments of biomass and methods to assess their efficacy are crucial for biomass-to-biofuels research and technology. Here, we applied confocal and fluorescence lifetime imaging microscopy (FLIM) using one- and two-photon excitation to map the lignin distribution within bagasse fibers pretreated with acid and alkali. The evaluated spectra and decay times are correlated with previously calculated lignin fractions. We have also investigated the influence of the pretreatment on the lignin distribution in the cell wall by analyzing the changes in the fluorescence characteristics using two-photon excitation. Eucalyptus fibers were also analyzed for comparison.ResultsFluorescence spectra and variations of the decay time correlate well with the delignification yield and the lignin distribution. The decay dependences are considered two-exponential, one with a rapid (τ1) and the other with a slow (τ2) decay time. The fastest decay is associated to concentrated lignin in the bagasse and has a low sensitivity to the treatment. The fluorescence decay time became longer with the increase of the alkali concentration used in the treatment, which corresponds to lignin emission in a less concentrated environment. In addition, the two-photon fluorescence spectrum is very sensitive to lignin content and accumulation in the cell wall, broadening with the acid pretreatment and narrowing with the alkali one. Heterogeneity of the pretreated cell wall was observed.ConclusionsOur results reveal lignin domains with different concentration levels. The acid pretreatment caused a disorder in the arrangement of lignin and its accumulation in the external border of the cell wall. The alkali pretreatment efficiently removed lignin from the middle of the bagasse fibers, but was less effective in its removal from their surfaces. Our results evidenced a strong correlation between the decay times of the lignin fluorescence and its distribution within the cell wall. A new variety of lignin fluorescence states were accessed by two-photon excitation, which allowed an even broader, but complementary, optical characterization of lignocellulosic materials. These results suggest that the lignin arrangement in untreated bagasse fiber is based on a well-organized nanoenvironment that favors a very low level of interaction between the molecules.

The Content of Different Hydrogen Bond Models and Crystal Structure of Eucalyptus Fibers during Beating

Different hydrogen bond and crystalline cellulose structure models of eucalyptus fibers were studied by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), and Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (CP/MAS 13C NMR). It was shown that when the beating time was increased from 5 to 15 min., the content of inter-molecular hydrogen bonds, O(6)H···O3′, increased by 11.2% as measured by FTIR. However, the content of the inter-molecular hydrogen bonds decreased quickly as the beating time was increased from 15 to 25 min. Meanwhile, the contents of the intra-molecular hydrogen bond, O(2)H···O(6) and O(3)H···O(5), changed from 8.25% to 8.18% and from 39.33% to 31.27%, respectively, when the beating time increased from 5 to 15 min. The content of the intra-molecular hydrogen bonds increased quickly with the further increase in the beating time. It was shown by XRD that there was a little difference in the average width of crystallite size in the (002) lattice plane when the beaten time was between 5 to 25 min. Non-linear fitting of the cellulose C4 region of the 13C CP/MAS NMR showed that the average lateral fibril aggregate dimensions and the content of different cellulose polymorphs changed during beating.

Characterisation of the bending stiffness components of MDF panels from full-field slope measurements

This paper deals with the characterisation of bending stiffness components of medium density fibreboard (MDF) by carrying out a single plate bending test. The approach couples full-field slope measurements with an inverse identification method. MDF panels manufactured with different fractions of Eucalyptus fibres and sugarcane bagasse particles were used. The slope maps generated across the plate surface were measured by the deflectometry technique. The curvature fields of the deformed plate were reconstructed by numerical differentiation afterwards. The virtual fields method was then implemented for material parameter identification under the framework of Kirchhoff–Love plate bending theory. The elastic properties obtained from the proposed data reduction (i.e. simultaneous identification of modulus of elasticity, Poisson’s ratio and shear modulus) were compared with values determined from classical three-point bending tests and reported in the literature. The set of properties were found in relatively good agreement.

Processing Changes of Cement Based Composites Reinforced with Silane and Isocyanate Eucalyptus Modified Fibres

Fibre-cement products had been widely used in the world due to their versatility as corrugated and flat roofing materials, cladding panels and water containers presented in large number of building and agriculture applications. The main reason for incorporating fibres into the cement matrix is to improve the toughness, tensile strength, and the cracking deformation characteristics of the resultant composite. One of the drawbacks associated with cellulose fibres in cement application is their dimensional instability in the presence of changing relative humidity. The objective of the present work is to evaluate the effect of surface treatment of eucalyptus cellulose pulp fibres on the processing and dimensional changes of fibre-cement composites. Surface modification of the cellulose pulps was performed with methacryloxypropyltri-methoxysilane (MPTS), aminopropyltri-ethoxysilane (APTS) and n-octadecyl isocyanate, an aliphatic isocyanate (AI), in an attempt to improve their dimensional instability into fibre-cement composites. X-ray photoelectron spectroscopy (XPS) showed the chemical changes occurred at the surface, and contact angle measurements showed the changes in the surface energy. MPTS-and AI-treated fibres presented lower hydrophilic character than untreated fibres, which led to lower water retention values (WRV). APTS increased the water retention value of the pulp and improved the capacity of hydrogen bonding of the fibres. MPTS-and AI-treated fibres led to low final water/cement ratios and reduced volume changes after pressing. MPTS-treated fibres decreased the water and dimensional instability of the fibre-cement composites, while the contrary occurred with APTS-modified and AI-modified fibres.These results are promising and contribute for new strategy to improve processing and stability of natural fibres-reinforced cement products.

Study on the modification of bleached eucalyptus kraft pulp using birch xylan

Abstract In this study, birch xylan was deposited onto elementally chlorine free (ECF) bleached eucalyptus kraft pulp, and the corresponding changes in physical properties were determined. An aqueous 5% birch xylan solution at pH 9 was added to 5 wt% slurry of bleached kraft eucalyptus fibers, with stirring at 70 °C for 15 min after which the pH was adjusted to 5–6. The xylan enriched fibers were isolated by filtration and used for physical testing. A 1.15 wt% adsorption of birch xylan on the kraft fibers at 8% xylan addition increased the tensile index, strain and tensile energy absorption values by ∼10%, while the burst index increased by 20.15%. The tear index increased by 2.55% with the adsorption of 0.87 wt% birch xylan on the eucalyptus kraft pulp at 3% xylan addition. The pulp beatability was also improved by adding birch xylan. The surface morphology of the unmodified and modified pulp samples were analyzed using atomic force microscopy (AFM) in the tapping mode. The analysis revealed the differences in the fine structure of fibers which showed micrometer-sized xylan structures spreading over the fiber surfaces.

Mechanical and thermal properties of eucalyptus fiber composites bonding by blocked polyurethane adhesive

In this work, composites from eucalyptus fiber (EF) and polyurethane emulsion (PU) were prepared. Ethyl cellosolve-blocked polyisocyanate (EC-bp) was used as a novel adhesive and the mechanical and water absorption properties of the prepared composites were analyzed. The results showed that the tensile, flexural, and water resistance properties of the composites modified by such adhesive were enhanced compared with those of unmodified ones. Effects of EC-bp on the thermal degradation and the morphology of the composites were also investigated and compared. The presence of modification on the surface of EC-bp treated EF/PU composites was identified by Fourier transform infrared spectroscopy (FTIR) from the appearance of CO bands absorbance and the reducing of relative intensity of OH. Thermo-gravimetric analysis (TGA) resulted that the thermal stability of the modified composites was improved. Environmental scanning electron microscopy (ESEM) was used to observe the morphology and evaluate the interfacial adhesion of the composites. The results showed that much better homogeneity morphology of the modified composites was achieved, which indicated that the prepared EC-bp as an adhesive could improve the interfacial adhesion. These findings appeared that the occurrence of strong bonds between the composite components in the presence of EC-bp, rather than the unique existence of Van der Waals interactions among the nonpolar structures or the hydrogen bonding interaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Pilot study for MDF manufacture from sugarcane bagasse and eucalyptus fibers

As an innovation in scientific research and development of a new product and with the objective of adding value to sugarcane bagasse, laboratory panels were made with 0%, 25%, 50%, 75% and 100% particles from Saccharum spp bagasse mixed with Eucalyptus grandis fibers, a raw material traditionally used for MDF panels in Brazil. The physical and mechanical properties of the panels were evaluated according to EN 622-5 (1997). The results indicated that panels with up to 75% bagasse showed average physical and mechanical property values that meet the current specification, thus opening up the prospect of using this abundant agricultural fiber resource.

Pulping and papermaking properties of Tunisian Alfa stems ( Stipa tenacissima)—Effects of refining process

The objective of this work is to study characteristics of chemical pulps (soda cooking process) and of paper obtained from Alfa, also known as Stipa tenacissima. For this purpose, Tunisian Alfa stems, and both unbleached and bleached pulps were characterized by determining their chemical composition as well as their morphological and physical properties. Through a detailed comparison with the other pulps obtained from various species, we show that the properties of Alfa stem fibres are intermediate between those of non-wood and wood plants, and most often close to those of Eucalyptus fibres. Refining process (PFI mill device) was then applied to the unbleached and bleached Alfa pulps. The modifications of the morphological properties of the fibres and the drainability and water retention values of the pulps were studied as a function of the refining degree. Here again, Alfa fibres exhibit a behaviour similar to that of Eucalyptus fibres, as the fibre shortening is very limited during the refining process. Finally, conventional handsheets with a basis weight of 65 g/m 2 were prepared from the unrefined and refined pulps. Their characterization showed that Alfa based papers present low density values and quite good mechanical properties, which are significantly enhanced by the refining treatment, particularly for the unbleached pulp. This study demonstrates the high potentiality of this non-wood species for papermaking applications.

A Study of the Physical and Mechanical Properties of Paper Made from Agave americana L. Fibers

This article studies the influence of the pulping conditions of Agave americana L. [temperature (100–120°C), pulping time (60–120 mn) and soda concentration (4–8%)] on the pulp yield, kappa index, brightness, viscosity, and the hand sheets breaking length, tear index, and burst index. Responses of pulp and hand sheets properties to the process variables were analyzed using statistical software (Minitab 14). Pulp has been studied using a factorial design to identify the optimum operating conditions, equations relating the dependant variables to the operational variables of the pulping process were established. Results showed that acceptable physical and mechanical properties of pulps and paper could be achieved at 107°C, for 60 mn, and 6% of soda concentration. These are the most suitable conditions for obtaining paper sheets with a high breaking length and tear and burst indexes. Test sheets made from pulped agave leaf fibers were compared to paper made from other vegetable fibers (pine, agave tequilana, and eucalyptus fibers).