Optimal Design of Ozone Bleaching Parameters to Approach Cellulose Nanofibers Extraction from Sugarcane Bagasse Fibers

Cellulose nanofibers (CNFs) were isolated from sugarcane bagasse (SCB) through the combination of bio-refinery, sulfur-free, and totally chlorine free (TCF) chemo-mechanical pretreatments, with a focus on the optimal design of ozone bleaching parameters based on a response surface methodology (RSM). For this purpose, the most effective parameters in ozone bleaching (temperature, time, and pulp consistency) were set between 40 and 85 °C, 60 and 360 min, and 1–5 wt%, respectively. High-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), Kappa number, and scanning electron microscopy (SEM) were used to chemically and morphologically characterize the SCB fibers. The size distribution and morphology of CNFs were also evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). HPLC analysis revealed that percentage of cellulose increased from 41.5 to 91.39% after chemical pretreatments. FTIR and Kappa number analyses also confirmed the successful isolation of cellulose fibers from the SCB fibers after chemical pretreatments. Furthermore, DLS results showed that the hydrodynamic diameter of the isolated cellulose fibers reduced to 268 nm by dint of ultrasonication. Additionally, TEM images confirmed the isolation of CNFs: the average diameter of cellulose fibers decreased to about 28 nm after mechanical steps and the yield of fibrillation was found to be around 99%. According to the obtained results, the applied chemo-mechanical treatment appears to be promising for green and facile isolation of CNFs.     

Fungal-modification of Natural Fibers: A Novel Method of Treating Natural Fibers for Composite Reinforcement

Growing interest in green products has provided fresh impetus to the research in the field of renewable materials. Plant fibers are not only renewable but also light in weight and low in cost. Polymer composites manufactured using them find applications in diverse fields such as automobiles, housing, and furniture. However, their hydrophilic nature and inadequate adhesion with matrix limits their use in high performance applications. In this study, a novel method for improving adhesion characteristics of natural fibers has been developed. This method is carried out by treating hemp fibers with a fungus: Ophiostoma ulmi, obtained from elm tree infected with Dutch elm disease. Treated fibers showed improved acid–base characteristics and resistance to moisture. Improved acid–base interactions between fiber and resin are expected to improve the interfacial adhesion, whereas improved moisture resistance would benefit the durability of the composites. Finally, composites were prepared using untreated/treated fibers and unsaturated polyester resin. Composites with treated fibers showed slightly better mechanical properties, which is most probably due to improved interfacial adhesion.     

Properties of Regenerated Cellulose Short Fibers/Cellulose Green Composite Films

Green composites of regenerated cellulose short fibers/cellulose were prepared by dissolving cellulose in a green solvent of 7% NaOH/12% Urea aqueous solution that was pre cooled at ?12?°C. The effect of fiber loading on the tensile, optical, thermal degradation and cell viability was studied. The tensile properties of cellulose were improved by the regenerated cellulose fiber reinforcement. The interfacial bonding between the fibers and matrix was assessed using the fractographs and found it to be good.     

Micromechanical Tensile Testing of Cellulose-Reinforced Electrospun Fibers Using a Template Transfer Method (TTM)

A template transfer method (TTM) and a fiber fixation technique were established for fiber handling and micro tensile stage mounting of aligned and non-aligned electrospun fiber mats. The custom-made template had been precut to be mounted on a variety of collectors, including a rapidly rotating collector used to align the fibers. The method eliminated need for direct physical interaction with the fiber mats before or during the tensile testing since the fiber mats were never directly clamped or removed from the original substrate. By using the TTM it was possible to measure the tensile properties of aligned poly(methyl methacrylate) (PMMA) fiber mats, which showed a 250?% increase in strength and 450?% increase in modulus as compared to a non-aligned system. The method was further evaluated for aligned PMMA fibers reinforced with cellulose (4 wt%) prepared as enzymatically derived nanofibrillated cellulose (NFC). These fibers showed an additional increase of 30?% in both tensile strength and modulus, resulting in a toughness increase of 25?%. The fracture interfaces of the PMMA?CNFC fibers showed a low amount of NFC pull-outs, indicating favorable phase compatibility. The presented fiber handling technique is universal and may be applied where conservative estimates of mechanical properties need to be assessed for very thin fibers.     

A Two-Step Chemical Process for the Extraction of Cellulose Fiber and Pectin from Mulberry Branch Bark Efficiently

In this work, a two-step method for the extraction of pectin and cellulose fiber from mulberry branch bark, a by-product of sericultural industry, was described. The method was based on the acid extraction of pectin and subsequently alkali treatment for obtaining cellulose fibers. The obtained pectin was high purity with the total galacturonic acid content of 85.46% ± 2.76% and the degree of esterification of 71.13% ± 1.67%. The chemical composition analysis, FTIR spectroscopy, XRD and TG analysis were used to characterize the cellulose fiber at different processing stages. After the two-step chemical process, the cellulose content was increased from 37.38% in original bark to 92.60% in cellulose fiber. The FTIR spectra revealed the removal of pectin, hemicelluloses and lignin from the bark by acid extraction and alkali treatment. The XRD and TG results indicated that the obtained cellulose fibers were with the increased crystallinity and thermal stability, whose crystallinity and degradation temperature were 86.36% ± 5.56% and 355 °C, respectively. This work may provide a new approach for high utilization of mulberry branch bark.     

Surface Modification of Sisal Fibers (Agave sisalana) Using Bacterial Cellulase and Methyl Methacrylate

The hydrophilic nature of cellulose fibers often results in poor compatibility with hydrophobic polymer matrices. Therefore, it becomes necessary to modify the surface of natural fiber for better binding between fiber and matrix. Chemicals are commonly used for the modification of cellulosic materials but large amount of solvents are usually involved. Microwave radiation induced grafting is one of the promising methods for the surface modification of natural fibers. In the present paper, we have reported the microwave radiations induced grafting onto sisal fibers (Agave sisalana) using methyl methacrylate monomer, which has been compared to the surface modification of sisal fibers using bacterial cellulase. The effects of these treatments on the properties of sisal fibers are discussed in the present paper. The modified fibers were characterized by scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis/differential thermal analysis techniques to determine their morphology, crystallinity and thermal stability.     

Biobased Fiber Production: Enzyme Retting for Flax/Linen Fibers

Flax (Linum ustitatissimum L.) is the source of natural fibers that provides biobased products for a variety of existing markets, but considerable processing and cleaning is required. Flax fibers, and bast fibers generally, are produced in the outer regions of the stem between bark and inner core tissues and require retting, which is the microbial separation of fiber from nonfiber tissues, as the first and most limiting stage of processing. Enzyme retting offers a method to overcome disadvantages of the current method, i.e., dew-retting, for high- and consistent-quality fibers with tailored properties for specific applications. Using chemical analyses, microscopy, and microspectroscopy, sites of carbohydrates, aromatics, and waxes plus cutins were identified in flax stems and their relationship to effective enzyme retting determined. Aromatics occur mostly in the inner, core tissues, with the fibers containing only small amounts located sporadically in cell corners of fiber bundles. Therefore, effective retting using enzymes to separate the aromatic-containing tissues from the fibers, but not to degrade aromatic compounds per se, is required. Waxes and cutin in the epidermal regions are effective barriers to enzyme penetration, and mechanical disruption facilitates enzyme penetration into the stems. Pectinases, with chelators to remove Ca⁺⁺ and destabilize pectin molecules, remove matrix compounds holding fibers within the stem and have been used in effective formulations to ret flax stems.     

Lignin-based Carbon Fibers: Effect of Synthetic Polymer Blending on Fiber Properties

Carbon fibers have been produced from hardwood lignin/synthetic polymer blend fibers. Hardwood kraft lignin was thermally blended with two recyclable polymers, poly(ethylene terephthalate) (PET) and polypropylene (PP). Both systems were easily spun into fibers. A thermostabilization step was utilized prior to carbonization to prevent fusion of individual fibers. For the lignin-based carbon fibers, careful control of heating rate was required. However, PET–lignin blend fibers can be thermostabilized under higher heating rates than the corresponding homofibers. Carbon fiber yield decreased with increasing incorporation of synthetic plastic. However, carbon fiber yield obtained for a 25% plastic blend fiber was still higher than that generally reported for petroleum pitch. Blend composition also affected surface morphology of the carbon fibers. Immiscible lignin–PP fibers resulted in a hollow and/or porous carbon fiber; whereas carbon fiber produced from miscible lignin–PET fibers have a smooth surface. Synthetic polymer blending also affected the mechanical properties of the fibers, especially MOE; lignin-based carbon fiber properties improved upon blending with PET.     

Effects of Alkali Treatment on the Properties of Short Flax Fiber–Poly(Lactic Acid) Eco-Composites

In this study, the influence of alkali (NaOH) treatment on the mechanical, thermal and morphological properties of eco-composites of short flax fiber/poly(lactic acid) (PLA) was investigated. SEM analysis conducted on alkali treated flax fibers showed that the packed structure of the fibrils was deformed by the removal non-cellulosic materials. The fibrils were separated from each other and the surface roughness of the alkali treated flax fibers was improved. The mechanical tests indicated that the modulus of the untreated fiber/PLA composites was higher than that of PLA; on the other hand the modulus of alkali treated flax fiber/PLA was lower than PLA. Thermal properties of the PLA in the treated flax fiber composites were also affected. T_g values of treated flax fiber composites were lowered by nearly 10 °C for 10% NaOH treatment and 15 °C for 30% NaOH treatment. A bimodal melting behavior was observed for treated fiber composites different than both of neat PLA and untreated fiber composites. Furthermore, wide angle X-ray diffraction analysis showed that the crystalline structure of cellulose of flax fibers changed from cellulose-I structure to cellulose-II.     

Preparation and Fundamental Characterization of Cellulose Nanocrystal from Oil Palm Fronds Biomass

The objective of this work was to isolate cellulose nanocrystal (CNC) from oil palm fronds (Elaeis guineensis) and its subsequent characterization. Isolation involves sodium hydroxide/anthraquinone pulping with mechanical refining followed by total chlorine free bleaching (includes oxygen delignification, hydrogen peroxide oxidation and peracetic acid treatment) before acid hydrolysis. Bleaching significantly decreased kappa number and increased α-cellulose percentage of fibers as confirmed by Technical Association of the Pulp and Paper Industry standards. Transmission electron microscopy (TEM), X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis revealed that acid hydrolysis along with bleaching improved crystallinity index and thermal stability of the extracted nanocrystals. It was observed that CNC maintained its cellulose 1 polymorph despite hydrolysis treatment. Mean diameter as observed by TEM and average fiber aspect ratio of obtained CNC was 7.44 ± 0.17 nm and 16.53 ± 3.52, respectively making it suitable as a reinforcing material for nanocomposite.     

Poly(lactic acid)/Cellulose Composites Obtained from Modified Cotton Fibers by Successive Acid Hydrolysis

This work is focused on the hydrolysis of cotton fibers from waste textiles to obtain micro and nanofibers to be used as reinforcements in polymer composites. To promote their compatibility with polymeric matrix, hydrolyzed cotton fibers were surface modified with various silane compounds. Thus, these fibers were mixed with commercial poly(lactic acid) (PLA) at 5% w/w loading by melt compounding. Acid treatments caused a decrease of the crystallinity index whereas the thermal stability was significantly improved, especially for cellulose fibers hydrolyzed in two steps. Morphological analysis revealed a reduction of the fibers diameter and a decrease of their length as a consequence of the hydrolysis. NMR analysis confirmed the silanization of the fibers by reaction with the silane agent. Tensile tests revealed that silanization treatments were able to increase the composite Young’s modulus and the stress at break with respect to the neat matrix, indicating that silanization improved the polymer/fiber compatibility interfacial adhesion. The overall results demonstrated that applying suitable surface modification strategies, waste cotton textiles can be effectively recycled as fillers in polymer based composites.     

Use of Industrial Hemp Fibers to Reinforce Wheat Gluten Plastics

The next generation of manufactured products must be sustainable and industrially eco-efficient, making materials derived from plants an alternative of particular interest. Wheat gluten (WG) is an interesting plant material to be used for production of plastic similar materials due to its film-forming properties. For usage of plastics in a wider range of applications, composite materials with improved mechanical properties are demanded. The present study investigates the possibilities of reinforcing WG plastics with hemp fibers. Samples were manufactured using compression molding (130 °C, 1600 bar, 5 min). Variation in fiber length, content (5, 10, 15 and 20 wt%) and quality (poor, standard, good) were evaluated. Mechanical properties and structure of materials were examined using tensile testing, light and scanning electron microscopy. Hemp fiber reinforcement of gluten plastics significantly influenced the mechanical properties of the material. Short hemp fibers processed in a high speed grinder were more homogenously spread in the material than long unprocessed fibers. Fiber content in the material showed a significant positive correlation with tensile strength and Young’s modulus, and a negative correlation with fracture strain and strain at maximum stress. Quality of the hemp fibers did not play any significant role for tensile strength and strain, but the Young’s modulus was significantly and positively correlated with hemp fiber quality. Despite the use of short hemp fibers, the reinforced gluten material still showed uneven mechanical properties within the material, a result from clustering of the fibers and too poor bonding between fibers and gluten material. Both these problems have to be resolved before reinforcement of gluten plastics by industrial hemp fibers is applicable on an industrial scale.     

All-Cellulose Composite Fibers Obtained by Electrospinning Dispersions of Cellulose Acetate and Cellulose Nanocrystals

All-cellulose composite fibers were produced by electrospinning dispersions containing cellulose acetate (CA) and cellulose nanocrystals (CNCs). Precursor polymer matrices were obtained after dispersion of CA with different degrees of substitution in a binary mixture of organic solvents. The obtained fibers of CA loaded with CNCs had typical widths in the nano- and micro-scale and presented a glass transition temperature of 145?°C. The CA component was converted to cellulose by using alkaline hydrolysis to yield all-cellulose composite fibers that preserved the original morphology of the precursor system. Together with Fourier Transform Infrared Spectroscopy fingerprints the thermal behavior of the all-cellulose composite fibers indicated complete conversion of cellulose acetate to regenerated cellulose. Noticeable changes in the thermal, surface and chemical properties were observed upon deacetylation. Not only the thermal transitions of cellulose acetate disappeared but the initial water contact angle of the web was reduced drastically. Overall, we propose a simple method to produce all-cellulose composite fibers which are expected to display improved thermo-mechanical properties while keeping the unique features of the cellulose polymer.     

Cellulose Fiber Isolation and Characterization from Sweet Blue Lupin Hull and Canola Straw

In this study, cellulose fibers were removed from crop by-products using a combination of sodium hydroxide treatment followed by acidified sodium chlorite treatment. The objective was to obtain high recovery of cellulose by optimizing treatment conditions with sodium hydroxide (5–20%, 25–75 °C and 2–10 h) followed by acidified sodium chlorite (1.7%, 75 °C for 2–6 h) to remove maximum lignin and hemicellulose, as well as to investigate the effect of lignin content of the starting materials on the treatment efficiency. Samples were characterized for their chemical composition, crystallinity, thermal behavior and morphology to evaluate the effects of treatments on the fibers’ structure. The optimum sodium hydroxide treatment conditions for maximum cellulose recovery was at 15% NaOH concentration, 99 °C and 6 h. Subsequent acidified sodium chlorite treatment at 75 °C was found to be effective in removing both hemicellulose and lignin, resulting in higher recovery of cellulose in lupin hull (~?95%) and canola straw (~?93%). The resultant cellulose fibers of both crop by-products had increased crystallinity without changing cellulose I structure (~?68–73%). Improved thermal stabilities were observed with increased onset of degradation temperatures up to 307–318 °C. Morphological investigations validated the effectiveness of treatments, revealing disrupted cell wall matrix and increased surface area due to the removal of non-cellulosics. The results suggest that the optimized combination of sodium hydroxide and acidified sodium chlorite treatments could be effectively used for the isolation of cellulose fibers from sweet blue lupin hull and canola straw, which find a great number of uses in a wide range of industrial applications.     

Preparation and Properties of Green Composites Based on Tapioca Starch and Differently Recycled Paper Cellulose Fibers

Green composites obtained from biodegradable renewable resources have gained much attention due to environmental problems resulting from conventionally synthetic plastics and a global increasing demand for alternatives to fossil resources. In this work we used different cellulose fibers from used office paper and newspaper as reinforcement for thermoplastic starch (TPS) in order to improve their poor mechanical, thermal and water resistance properties. These composites were prepared by using tapioca starch plasticized by glycerol (30 % wt/wt of glycerol to starch) as matrix reinforced by the extracted cellulose fibers with the contents ranging from 0 to 8 % (wt/wt of fibers to matrix). Properties of composites were determined by mechanical tensile tests, differential scanning calorimetry, thermogravimetric analysis, water absorption measurements, scanning electron microscopy, and soil burial tests. The results showed that the introduction of either office paper or newspaper cellulose fibers caused the improvement of tensile strength and elastic modulus, thermal stability, and water resistance for composites when compared to the non-reinforced TPS. Scanning electron microscopy showed a good adhesion between matrix and fibers. Moreover, the composites biological degraded completely after 8 weeks but required a longer time compared to the non-reinforced TPS. The results indicated that these green composites could be utilized as commodity plastics being strong, inexpensive, plentiful and recyclable.     

A novel process for ethanol or biogas production from cellulose in blended-fibers waste textiles

A novel process has been developed for separation of the cellulose, i.e. cotton and viscose, from blended-fibers waste textiles. An environmentally friendly cellulose solvent, N-methylmorpholine-N-oxide (NMMO) was used in this process for separation and pretreatment of the cellulose. This solvent was mixed with blended-fibers textiles at 120 °C and atmospheric pressure to dissolve the cellulose and separate it from the undissolved non-cellulosic fibers. Water was then added to the solution in order to precipitate the cellulose, while both water and NMMO were reused after separation by evaporation. The cellulose was then either hydrolyzed by cellulase enzymes followed by fermentation to ethanol, or digested directly to produce biogas. The process was verified by testing 50/50 polyester/cotton and 40/60 polyester/viscose-blended textiles. The polyesters were purified as fibers after the NMMO treatments, and up to 95% of the cellulose fibers were regenerated and collected on a filter. A 2-day enzymatic hydrolysis and 1-day fermentation of the regenerated cotton and viscose resulted in 48 and 50 g ethanol/g regenerated cellulose, which were 85% and 89% of the theoretical yields, respectively. This process also resulted in a significant increase of the biogas production rate. While untreated cotton and viscose fibers were converted to methane by respectively, 0.02% and 1.91% of their theoretical yields in 3 days of digestion, the identical NMMO-treated fibers resulted into about 30% of yield at the same period of time.     

Influence of Fibers on the Mechanical Properties of Cassava Starch Foams

The utilization of renewable resources in packaging can provide solutions to ecological problems such as waste quantity. Agricultural resources are alternative raw materials, among which there is starch, a natural polysaccharide that can be used to form resistant foam under wet and warm conditions. The starch foam is obtained by thermo pressing process where cassava starch, water and additives are processed to form a rigid structure by swelling, gelatinization and network formation. Natural fibers can be used to improve the mechanical properties of starch foams. In this project was investigated the influence of the addition of fibers in the levels of 1, 2 and 3% of cassava (short fiber) and 1, 2 and 3% of wheat fiber (powered fiber) in the starch dough. The foams were characterized by physical methods of strength, flexibility, density and by Scanning Electron Microscopy (SEM). The increase in fibers quantity has resulted in foams with higher density and less flexibility, whatever the fiber type. Most fibers quantity did not improve the foam strength. Foam made with 1% of cassava fiber showed higher compression strength; by increasing the percentage quantity there was a decrease on the compression resistance. Foam made with wheat fiber presented a lower result in 2%. The fiber type had no statistical significance in strength, flexibility and density foam. Only the fiber quantity was significant. The results showed that both fibers presented limited dimensions to improve the reinforcement of the starch foams up to 1%.     

Chemically Modified Banana Fiber: Structure,Dielectrical Properties and Biodegradability

Banana fibers, as well as other lignocellulosic fibers, are constituted of cellulose, hemicellulose, lignin, pectin, wax and water soluble components. The abundance of this fiber combined with the ease of its processing is an attractive feature, which makes it a valuable substitute for synthetic fibers that are potentially toxic. In this work, the structure characterization of the banana fiber modified by alkaline treatment was studied. Some important properties of this fiber changed due to some chemical treatments, such as the crystalline fraction, dielectric behavior, metal removal (governed by solution pH) and biodegradation. Our results showed that treated banana fiber is a low cost alternative for metal removal in aqueous industry effluents. Thus, for regions with low resources, the biosorbents are an alternative to diminish the impact of pollution caused by local industries, besides being a biodegradable product.     

Effect of Coconut, Sisal and Jute Fibers on the Properties of Starch/Gluten/Glycerol Matrix

Coconut, sisal and jute fibers were added as reinforcement materials in a biodegradable polymer matrix comprised of starch/gluten/glycerol. The content of fibers used in the composites varied from 5% to 30% by weight of the total polymers (starch and gluten). Materials were processed in a Haake torque rheometer (120 °C, 50 rpm) for 6 min. The mixtures obtained were molded by heat compression and further characterized. Addition of lignocellulosic fibers in the matrix decreased the water absorption at equilibrium. The diffusion coefficient decreased sharply around 5% fiber concentration, and further fiber additions caused only small variations. The thermogravimetric (TG) analysis revealed improved thermal stability of matrix upon addition of fibers. The Young’s modulus and ultimate tensile strength increased with fiber content in the matrix. The storage modulus increased with increasing fiber content, whereas tanδ curves decreased, confirming the reinforcing effect of the fibers. Morphology of the composites analyzed under the scanning electron microscope (SEM) exhibited good interfacial adhesion between the matrix and the added fibers. Matrix degraded rapidly in compost, and addition of increased amounts of coconut fiber in the matrix caused a slowdown the biodegradability of the matrix. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may be suitable.     

TPS/PCL Composite Reinforced with Treated Sisal Fibers: Property, Biodegradation and Water-Absorption

Sisal fibers bleached with sodium-hydroxide followed by hydrogen peroxide treatment were incorporated in a thermoplastic starch/ε-polycaprolactone (TPS/PCL) blend via extrusion processing. These samples with smooth and homogenous surfaces were examined for their property, biodegradability and water absorption. Scanning electron microscopy revealed that the fibers were well dispersed in the matrix. In addition, it was found that the fibers and matrices interacted strongly. Blends with 20 % (dry weight-basis) fiber content showed some fiber agglomeration. Whereas blends with 10 % fibers showed increased crystallinity and lower water absorption capacity. The CO₂ evolution study showed that the thermoplastic starch samples without any additives had the highest rate and extent of degradation whereas the neat PCL samples had the lowest degradation rate. Addition of fiber to the TPS/PCL blend exhibited the degradation rates and extents that were somewhere in between the pure TPS and neat PCL. This work demonstrates that TPS/PCL composites reinforced with bleached sisal has superior structural characteristics and water resistance and thus, can be used as polymeric engineering composites for different applications.