Monitoring the polymerization process of polypyrrole films by thermogravimetric and X-ray analysis

Bio-composite fibers were developed from wood pulp and polypropylene (PP) by an extrusion process. The thermo-physical and mechanical properties of wood pulp-PP composite fibers, neat PP and wood pulp were studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermal stability of bio-composite fibers was found to be significantly higher than pure wood pulp. An understanding into the melting behaviour of the composite system was obtained which would assist in selecting a suitable temperature profile for the extruder during processing. The visco-elastic properties of bio-composite fibers were also revealed from the study. The generated bio-composite fibers were also characterized using Fourier transform infrared spectroscopy (FTIR) to understand the nature of chemical interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Changes in absorption peaks were observed in FTIR spectra of bio-composite fibers as compared to the pure wood pulp which indicated possible chemical linkages between the fiber and polymer matrix.     

Physico-chemical and anatomical characterization of residual lignocellulosic fibers

Anatomical and physico-chemical properties of residual natural fibers (sugarcane bagasse, coconut fibers and peanut hulls) were characterized in order to evaluate their potential for use in the production of particleboard. The bulk density was determined by helium pycnometer and the chemical characteristics by using an electronic pH meter (for pH determination) on fibers dissolved in acidic and neutral detergents (to determine the levels of cellulose, hemicellulose and lignin). The anatomical characteristics were established using scanning electron microscopy coupled with an X-ray detector system, as well as energy dispersive X-ray spectroscopy. Results indicated similarities and differences between physico-chemical and anatomical characteristics of the residual lignocellulosic fibers when compared with the Pinus sp. wood commercially employed in particleboard production. Bulk density and pH for residual lignocellulosic fibers and Pinus sp. wood presented analogous values. Similar amounts of cellulose and lignin were identified between waste fibers and Pinus sp. wood. The presence of silica was identified in coconut fiber, peanut hull and sugarcane bagasse waste fibers, and may affect the mechanical characteristics of panels. Coconut and sugarcane bagasse fibers show surface pores with diameters ranging from 1.2 to 2.1 μm, below the 5 μm identified for Pinus sp. wood. Both fibers present pores distributed over their entire surface, whereas peanut hull fibers have no pores on their surface. This characteristic contributes to resin dispersion among particles, reflecting positively on the physical–mechanical properties of the panels. Particleboards produced with residual lignocellulosic fibers present similar physical–mechanical properties to those of Pinus sp. wood panels.     

Sulfur-free dissolving pulps and their application for viscose and lyocell

In this study, the concept of multifunctional alkaline pulping has been approved to produce high-purity and high-yield dissolving pulps. The selective removal of hemicelluloses was achieved by either water autohydrolysis (PH) or alkaline extraction (E) both applied as pre-treatments prior to cooking. Alternatively, hemicelluloses were isolated after oxygen delignification in a process step denoted as cold caustic extraction (CCE). Eucalyptus globulus wood chips were used as the raw material for kraft and soda-AQ pulping. In all process modifications sulfur was successfully replaced by anthraquinone. By these modifications purified dissolving pulps were subjected to TCF bleaching and comprehensive viscose and lyocell application tests. All pulps met the specifications for dissolving pulps. Further more, CCE-pulps showed a significantly higher yield after final bleaching. Morphological changes such as ultrastructure of the preserved outer cell wall layers, specific surface area and lateral fibril aggregate dimension correlated with the reduced reactivity towards regular viscose processing. The residual xylan after alkali purification depicted a lower content of functional groups and a higher molecular weight and was obviously entrapped in the cellulose fibril aggregates which render the hemicelluloses more resistant to steeping in the standard viscose process. Simultaneously, the supramolecular structure of the cellulose is partly converted from cellulose I to cellulose II by the alkaline purification step which did not influence the pulps reactivity significantly. Nevertheless, these differences in pulp parameters did not affect the lyocell process due to the outstanding solubility of the pulps in NMMO. Laboratory spinning revealed good fiber strength for both, regular viscose and lyocell fibers. The high molecular weight xylan of the CCE-treated pulps even took part in fiber forming.     

Thermal analysis and spectroscopic studies of electrospun nano-scale composite fibers

The aim of this article is to develop nano-scale composite fibers from wood pulp, modified wood pulp, and polyethylene oxide (PEO). Composite fibers were developed in the diameter range of 339–612 nm. Alignment process of the composite fibers was done by electrostatic interactions between two collector disks. DSC results demonstrated a lower melting temperature of composite fibers than PEO powder. The development of crystalline structure in the composite fibers and acetylated wood pulp was poor. Thermogravimetric analysis revealed that the thermal stability of composite fibers were relatively lower than PEO powder. Fourier transform infrared spectroscopy (FTIR) showed significant differences between modified and unmodified wood pulp in the region of 960–1746 cm⁻¹. The peak intensity of acetylated wood pulp was appeared at 1746 cm⁻¹ because of acetyl groups. The composite fibers demonstrated the characteristic peak of PEO since less wood pulp was incorporated in the composite system.     

Effect of γ-ray radiation on the polyacrylonitrile based carbon fibers

To investigate the effect of γ-ray radiation on the microstructural and mechanical properties of carbon fibers, carbon fibers were irradiated by ⁶⁰Co source. The interlayer spacing d₀₀₂ of carbon fibers decreased after irradiation. The Young’s modulus and density of the fibers increased with increasing dose. The tensile strength of fibers was found to increase at low dose and decrease at high dose. Additionally, Compton scattering effect caused by γ-ray is proposed to be responsible for the structural and mechanical changes of fibers. The results indicated that γ-ray irradiation was an effective method for improving the mechanical properties and graphitization degree of polyacrylonitrile based carbon fibers.     

Castor oil-based biopolyurethane reinforced with wood microfibers derived from mechanical pulp

Wood fibers with high lignin content show promise to function in numerous applications with advantageous properties if the fiber features are appropriately exploited. The present study introduces a new approach to disintegrate and disperse wood fibers from groundwood pulp (GWP) directly to polyol without additional solvent exchanges or chemical modifications. In comparison bleached chemical pulp with low lignin content was ground in the polyol, but only low consistency (1 wt%) operation was possible, whereas up to 5 wt% consistency with GWP was carried out with ease. The micron sized fibers in polyol were reacted with polymeric diphenylmethane diisocyanate to produce fiber reinforced biopolyurethane (bioPU) composites. The mechanical properties of the composites improved compared to reference bioPU showing 14.6% increase in Young’s modulus, 54.5% in tensile strength and 26.1% in strain at break. The tan δ peaks shifted to higher temperature from 5.5 to 10.4 °C when fibers up to 5.1 wt% were incorporated to bioPU. Overall, the bulk microfibers from GWP with low degree of processing were cost-effective reinforcements for bioPUs, which improved the qualities of the fabricated composites and showed good compatibility with polyurethane.     

Cytotoxicity tests of cellulose nanofibril-based structures

Cellulose nanofibrils based on wood pulp fibres are most promising for biomedical applications. Bacterial cellulose has been suggested for some medical applications and is presently used as wound dressing. However, cost-efficient processes for mass production of bacterial cellulose are lacking. Hence, fibrillation of cellulose wood fibres is most interesting, as the cellulose nanofibrils can efficiently be produced in large quantities. However, the utilization of cellulose nanofibrils from wood requires a thorough verification of its biocompatibility, especially with fibroblast cells which are important in regenerative tissue and particularly in wound healing. The cellulose nanofibril structures used in this study were based on Eucalyptus and Pinus radiata pulp fibres. The nanofibrillated materials were manufactured using a homogenizer without pre-treatment and with 2,2,6,6-tetramethylpiperidine-1-oxy radical as pre-treatment, thus yielding nanofibrils low and high level of anionic charge, respectively. From these materials, two types of nanofibril-based structures were formed; (1) thin and dense structures and (2) open and porous structures. Cytotoxicity tests were applied on the samples, which demonstrated that the nanofibrils do not exert acute toxic phenomena on the tested fibroblast cells (3T3 cells). The cell membrane, cell mitochondrial activity and the DNA proliferation remained unchanged during the tests, which involved direct and indirect contact between the nano-structured materials and the 3T3 cells. Some samples were modified using the crosslinking agent polyethyleneimine (PEI) or the surfactant cetyl trimethylammonium bromide (CTAB). The sample modified with CTAB showed a clear toxic behaviour, having negative effects on cell survival, viability and proliferation. CTAB is an antimicrobial component, and thus this result was as expected. The sample crosslinked with PEI also had a significant reduction in cell viability indicating a reduction in DNA proliferation. We conclude that the neat cellulose nanostructured materials tested in this study are not toxic against fibroblasts cells. This is most important as nano-structured materials based on nanofibrils from wood pulp fibres are promising as substrate for regenerative medicine and wound healing.     

Cellulose Depolymerisation and Paper Properties in E. Globulus Kraft Pulps

The aim of this work was to study the impact of cellulose depolymerisation on the beating potential and handsheet properties of the portuguese E. globulus kraft pulp. A homogeneous sample of eucalypt wood chips was cooked using different kraft pulping conditions (cooking temperatures and times, and sodium hydroxide and sodium sulphide concentrations) in order to obtain a wide variation for intrinsic viscosity of the pulps. In the range of industrial cooking conditions, this property was found to be linearly dependent on the effective alkali charge, for a given cooking time and temperature. Unbeaten and beaten (at 2000 rev. PFI) pulp properties were evaluated and the results confirm that the higher the pulp intrinsic viscosity the better the pulp beatability and the paper properties. However, the differences in the latter cannot be exclusively explained by the differences in viscosity, since pulps with the same viscosity may exhibit distinct papermaking potentials. It was then necessary to scan other pulp chemical characteristics that could also influence the development of paper properties such as lignin, pentosan content and polysaccharides relative composition.     

The effect of chemical and physical characteristics of spruce SEW pulps on enzymatic hydrolysis

Conifers, which are the most abundant biomass species in Nordic countries, USA, Canada and Russia, exhibit strong resistance towards depolymerization by cellulolytic enzymes. At present, it is still not possible to isolate a single structural feature which would govern the rate and degree of enzymatic hydrolysis. On the other hand, the forest residues alone represent an important potential for biochemical production of biofuels. In this study, the effect of substrate properties on the enzymatic hydrolysis of softwood was studied. Stem wood spruce chips were fractionated by SO₂–ethanol–water (SEW) treatment to produce pulps of varying composition by applying different operating conditions. The SEW technology efficiently fractionates different types of lignocellulosic biomass by rapidly dissolving hemicelluloses and lignin. Cellulose remains fully in the solid residue which is then treated by enzymes to release glucose. The differences in enzymatic digestibility of the spruce SEW pulp fibers were interpreted in terms of their chemical and physical characteristics. A strong correlation between the residual lignin content of SEW pulp and enzymatic digestibility was observed whereas cellulose degree of polymerization and hemicellulose content of pulp were not as important. For the pulps containing about 1.5 % (w/w) lignin, 90 % enzymatic digestibility was achieved at 10 FPU enzyme charge and 24 h of hydrolysis time.     

Ionic liquid extraction method for upgrading eucalyptus kraft pulp to high purity dissolving pulp

High purity cellulose from wood is an important raw material for many applications such as cellulosic fibers, films or the manufacture of various cellulose acetate products. Hitherto, multi-step refining processes are needed for an efficient hemicellulose removal, most of them suffering from severe cellulose losses. Recently, a novel method for producing high purity cellulose from bleached paper grade birch kraft pulp was presented. In this so called IONCELL process, hemicelluloses are extracted by an ionic liquid–water mixture and both fractions can be recovered without yield losses or polymer degradation. Herein, it is demonstrated that bleached Eucalyptus urograndis kraft pulp can be refined to high purity acetate grade pulp via the IONCELL process. The hemicellulose content could be reduced from initial 16.6 to 2.4 wt% while persevering the cellulose I crystal form by using an optimized 1-ethyl-3-methylimidazolium dimethylphosphate-water mixture as the extraction medium. The degree of polymerization was then reduced by a sulfuric acid treatment for subsequent acetylation of the pulp, resulting in a final hemicellulose content of 2.2 wt%. When pre-treating the pulp enzymatically with endoxylanase, the final hemicellulose content could be reduced even to 1.7 wt%. For comparison, the eucalyptus kraft pulp was also subjected to cold caustic extraction and the same subsequent acid treatment which led to 3.9 wt% of residual hemicelluloses. The performance in acetylation of all produced pulps was tested and compared to commercial acetate grade pulp. The endoxylanase-IONCELL-treated pulp showed superior properties. Thus, an ecologically and economically efficient alternative for the production of highest value cellulose pulp is presented.     

Surface modification of lignocellulosic fibers using high-frequency ultrasound

Enzymatic and chemical oxidation of fiber surfaces has been reported in the literature as a method for producing medium density fiberboards without using synthetic adhesives. This work focuses on modifying the surface properties of wood fibers by the generation of free radicals using high-frequency ultrasound. A sonochemical reactor operating at 610 kHz is used to sonicate the aqueous suspensions of thermomechanical pulp fibers (TMP). TMP is analyzed using FTIR-transmission, FTIR-ATR spectroscopy and inverse gas chromatography (IGC). The non-conjugated carbonyl groups in TMP are represented by the peak area ratio A₁₇₃₆/A₁₅₁₁ in the FTIR-transmission spectra and by A₁₇₂₈/A₁₅₀₉ in the FTIR-ATR spectra. The increase in these ratios suggests that there is an increase in the number of non-conjugated carbonyl groups in TMP after sonication. To further investigate, sonication of the hydrolytic lignin was also carried out and analyzed using UV, UV-ionization and FTIR-transmission spectroscopy. The changes in the surface properties of the fibers are analyzed using IGC which showed an increase in the surface free energy of fibers. The effect of operating parameters such as power of ultrasound and sonication time is also studied.     

Enhanced Lignin Biodegradation by a Laccase-Overexpressed White-Rot Fungus Polyporus brumalis in the Pretreatment of Wood Chips

The laccase gene of Polyporus brumalis was genetically transformed to overexpress its laccase. The transformants exhibited increased laccase activity and effective decolorization of the dye Remazol Brilliant Blue R than the wild type. When the transformants were pretreated with wood chips from a red pine (softwood) and a tulip tree (hardwood) for 15 and 45 days, they showed higher lignin-degradation activity as well as higher wood-chip weight loss than the wild type. When the wood chips treated with the transformant were enzymatically saccharified, the highest sugar yields were found to be 32.5 % for the red pine wood and 29.5 % for the tulip tree wood, on the basis of the dried wood weights, which were 1.6-folds higher than those for the wild type. These results suggested that overexpression of the laccase gene from P. brumalis significantly contributed to the pretreatment of lignocellulose for increasing sugar yields.     

Production of Composite Materials from Peat and Wood by Explosive Autohydrolysis

Technology for obtaining peat and peat-wood composite materials by the explosive autohydrolysis method without using synthetic binders was developed. The optimal conditions of an explosive autohydrolysis of peat and peat in the presence of wood were found: pressure 1.62 MPa, temperature 210°C, treatment duration of 10 min in an explosive autohydrolysis reactor. Peat and peat-wood composite materials were obtained. In their strength characteristics (bending strength up to 14.68 MPa) and heat conductivity these materials compare well with the conventional heat-insulating materials and can be used as construction materials.

     

Analytical pyrolysis study of biodelignification of cloned Eucalyptus globulus (EG) clone and Pinus pinaster Aiton kraft pulp and residual lignins

This study centred on the analysis of lignin in situ of cloned eucalypt and pine kraft pulps. Trametes versicolor laccase-violuric acid system (LMS) delignifications were performed on a softwood (Pinus pinaster) and a hardwood (Eucalyptus globulus) conventional kraft pulp with an initial kappa number of 34.5 and 15.5, respectively. The LMS treated pulps were then subjected to alkaline extraction stages (E). The kappa number data show that LMS is effective at biodelignifying both softwood and hardwood kraft pulps. However, under the conditions employed in this study, a greater level of biodelignification was obtained with LMS E. globulus (hardwood) than with LMS P. pinaster (softwood), but the amount of lignin removed was higher for the softwood pulp. The original milled wood samples, kraft pulps, biodelignified kraft pulps, and isolated residual lignin and milled wood lignins from the two wood samples have been characterized by pyrolysis-gas chromatography/mass spectrometry. The analysis of the pyrograms indicates that the lignin compositions of the two wood species and corresponding pulps are very different, as expected; however, the knowledge of the chemical mechanisms of delignification is very limited and requires additional work. Analytical pyrolysis is one the few degradative methods for the analysis of biopolymers that has shown a sufficient degree of success.     

Analysis of impurities occurring in a totally chlorine free-bleached Kraft pulp

A set of impurities (specks) occurring in a TCF (totally chlorine free)-bleached Kraft pulp of Eucalyptus globulus wood was studied. The impurities were Soxhlet extracted with acetone, and the extracts subsequently analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) using high-temperature capillary columns. The lipophilic fraction isolated from E. globulus wood extractives was also analyzed for comparison. The composition of the acetone extracts was very similar to that of E. globulus wood. Fatty acids, steroid hydrocarbons, sterols, steroid ketones and sterol esters, arising from E. globulus wood extractives survived the cooking and bleaching processes and accumulated in the pulp. On the other hand, the residue left after acetone extraction was studied by pyrolysis–GC–MS. The results indicated that it was composed of small particles of polyisoprene rubber. In conclusion, the speck impurities studied here seems to be composed of two different moieties, a lipophilic part arising from wood extractives and a core of small particles of synthetic polymers (polyisoprene rubber).     

Buffalo Yogurt Fortified with Eucalyptus (Eucalyptus camaldulensis) and Myrrh (Commiphora Myrrha) Essential Oils: New Insights into the Functional Properties and Extended Shelf Life

Eucalyptus (Eucalyptus camaldulensis) and Myrrh (Commiphora Myrrha) essential oils (EOs) stand out for their benefits in terms of health and functionality. Buffalo set yogurt enriched with different concentrations of EOs (0.3, 0.6, and 0.9%) were investigated. The effects of addition on sensory, syneresis, antibacterial activity, and bioactive properties (total phenol content and antioxidant activity) of yogurt were studied. The most acceptable organoleptic properties of treated yogurt were those samples treated with Eucalyptus oil. The levels of syneresis were decreased by increasing the concentration of EOs. Moreover, the antioxidant activity, antibacterial activity, and total phenolic content were enhanced by increasing the concentration of EOs. Yogurt with 0.9% Eucalyptus oil showed the highest antioxidant activity and total phenolic content. The same concentration of Eucalyptus oil showed the highest antibacterial activity against S. typhimurium (the inhibition zone was 20.63 mm) then E. coli (the inhibition zone was 19.43 mm). On the other hand, the highest antibacterial effect against L. monocytogene was for Myrrh oil-enriched yogurt by 0.9% and the inhibition zone was 19.21 mm. The obtained results showed that Eucalyptus and Myrrh oils can be applied to yogurt to improve its beneficial properties in terms of physical characteristics and for human health due to their antioxidant activity and phenolic materials.     

Isolation and Characterization of Dimethyl Sulfide (DMS)-Degrading Bacteria from Soil and Biofilter Treating Waste Gas Containing DMS from the Laboratory and Pulp and Paper Industry

Dimethyl sulfide (DMS) is one of the sulfurous pollutants present in the waste gas generated from the pulp and paper industry. DMS has environmental health implications; therefore, it is necessary to treat the waste gas containing DMS prior to discharge into the environment. A bench-scale biofilter was operated in the laboratory as well as in a pulp and paper industry for the treatment of DMS. Both the biofilters were packed with pre-sterilized wood chips and cow dung/compost of the same origin seeded with biomass developed from garden soil enriched with DMS. The biofilters were operated for the generation of process parameters, and the potential microorganisms isolated from both the biofilters have been purified and characterized for degradation of DMS. Further, these cultures were purified on a basal medium using DMS as a sole carbon source for the growth. Further, the purified cultures were characterized through standard fatty acid methyl esters (FAME)-gas chromatography method, and the isolates were found to be mesophilic, aerobic microbes. These microbes were identified as Bacillus sphaericus-GC subgroup F, Paenibacillus polymyxa, B. sphaericus-GC subgroup F, B. sphaericus-GC subgroup F, and Bacillus megaterium-GC subgroup A, respectively. The potential culture for degradation of DMS was identified as B. sphaericus by 16s rRNA molecular analysis.     

Improved surface properties of CTMP fibers with enzymatic pretreatment of wood chips prior to refining

Surface properties of chemithermomechanical pulp (CTMP) fibers produced from enzymatically pretreated eucalyptus wood chips prior to refining were investigated by Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscope (TEM) and X-ray Photoelectron Spectroscopy (XPS). The results showed that in a traditional CTMP refining process most fiber disruptions occur in the middle lamella (ML) leaving behind a significant amount of hydrophobic materials on the resulting fiber surface. However, in a Bio-CTMP refining process, fiber fractures preferentially take place in the primary (P) and secondary 1 (S1) layers or the S1 and secondary 2 (S2) layers, which results in more fibrillation being generated in the subsequent refining thus improving inter-fiber bonding strength and paper strength. XPS chemical composition analysis together with pulp physical strength property showed that the surfaces of Bio-CTMP fibers become enriched with a greater proportion of carbohydrates in comparison with CTMP fiber surface, which supports FE-SEM and TEM observations.     

Valorization of Byproducts of Hemp Multipurpose Crop: Short Non-Aligned Bast Fibers as a Source of Nanocellulose

Nanocellulose was extracted from short bast fibers, from hemp (Cannabis sativa L.) plants harvested at seed maturity, non-retted, and mechanically decorticated in a defibering apparatus, giving non-aligned fibers. A chemical pretreatment with NaOH and HCl allowed the removal of most of the non-cellulosic components of the fibers. No bleaching was performed. The chemically pretreated fibers were then refined in a beater and treated with a cellulase enzyme, followed by mechanical defibrillation in an ultrafine friction grinder. The fibers were characterized by microscopy, infrared spectroscopy, thermogravimetric analysis and X-ray diffraction after each step of the process to understand the evolution of their morphology and composition. The obtained nanocellulose suspension was composed of short nanofibrils with widths of 5–12 nm, stacks of nanofibrils with widths of 20–200 nm, and some larger fibers. The crystallinity index was found to increase from 74% for the raw fibers to 80% for the nanocellulose. The nanocellulose retained a yellowish color, indicating the presence of some residual lignin. The properties of the nanopaper prepared with the hemp nanocellulose were similar to those of nanopapers prepared with wood pulp-derived rod-like nanofibrils.     

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

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