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The alkaline treatment condition plays a crucial role in governing the ultimate properties of flax fibers. In this study, flax fibers were modified with mild alkalization and severe mercerization conditions to give fundamental insight into how the molecular-scale changes in cell wall fine structure and cellulose supramolecular structure can affect...
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Context 1
... to the parallel up model proposed for cellulose I β ( Sarko and Muggli 1974) , as depicted in Figure 6(b), the unit cell is formed by the parallel configuration of chains that are situated in (200) planes along the c-axis, i.e. the fiber major axis. Each unit cell has two chains arranged with the same sense; the origin chain is positioned at the corner, and the center chain passes through the center of a/b plane so that it is translated by +1/4 c with respect to the origin one. ...
Context 2
... the other hand, according to the antiparallel model proposed for cellulose II (Kolpak and Blackwell 1976), as illustrated in Figure 6(c), the unit cell is formed by two chains in the same position as cellulose I β , but the origin and center chains are organized in (020) planes with alternating orientations. It is not possible stereochemically for all hydroxymethyl groups to retain the same transgauche conformation in the antiparallel arrangement. ...
Citations
... This infers that reinforcements act as a protective shield by forming a char and delaying the degradation process (Kanaginahal et al. 2023a). The decline observed in the unadulterated epoxy can be attributed to the cleavage of ether linkages and the degradation of carboxyl groups, arising from the pyrolysis of the interlinked molecular network (Bahrami, Bagheri, and Dai 2022;Manjula et al. 2018). The difference in the degradation values clearly infer the improvement in the properties attributed to the bonding at the interface which increased the sustainability of composites (Sahoo, Khandelwal, and Manik 2018). ...
Nowadays, synthetic fiber composites are in decline because of their high initial cost and detrimental impact on the environment. The main aim of this work is to develop natural fiber composite materials that are made from moringa and bamboo fibers by using the hand lay-up method by maintaining a constant 40 vol.% of epoxy content. Both the natural composites were treated with NaOH and also compared with their hybrid composite. The mechanical properties, such as compression, hardness, impact, tensile, flexural properties were investigated. Additionally, thermo gravimetric analysis of composites was also carried out. The biggest boost in compressive strength was seen in bamboo with 60% volume, with improvements ranging from a pure resin value of 13.06 to 68.43% compared to moringa 60% and 30–30% moringa-bamboo. The maximum rise in impact strength was recorded by BM-30/30 at 21J. In addition to this, the highest hardness value was observed by moringa-reinforced composites (MM-60) and noted to be around 40.83 HV. Tensile and flexural properties of all the composites reveal improvement as compared with neat epoxy composites. Bamboo exhibits a considerable improvement in thermal stability as compared with other compositions. Scanning electron micrographs were used to analyze the structure-property correlations.
... The types of functional groups and glycosidic linkages of dextran were also analyzed by FT-IR spectroscopic. In the dextran gels prepared at pH= 12, a new peak at 1540 cm − 1 confirmed the C --O stretch of carboxyl groups [51,[53][54][55]. When pH value reached 13, the peak at 1346 cm − 1 and 1280 cm − 1 disappeared, and the new peak at 1775 cm − 1 representing C --O bond provided evidence for the degradation of dextran [56]. ...
The release of hazardous NH3 toxic gas poses a significant threat to both the environment and human health, necessitating the development of materials capable of detecting NH3. This research focuses on the design of a fluorescent gel derived from the peeling-off reaction of Artemisia sphaerocephala Krasch. gum (ASKG). The variations in fluorescence intensity were examined for gels produced under different conditions of pH and adsorption capacity of NH3. The fluorescence response mechanism concerning NH3 and pH value was investigated through analysis of fluorescent lifetime, FT-IR, X-ray XPS, and GPC. Dextran was employed to validate this mechanism. The ASKG gel exhibited a rapid response to NH3 gas, and the fluorescence intensity demonstrated a linear correlation with the cumulative adsorption of NH3 gas. Pseudo-first-order kinetics was applied to analyze the adsorption system of the ASKG gel, revealing a maximum adsorption capacity of 0.03476 g/g for NH3. The practical application of the ASKG gel was demonstrated through a fish spoilage experiment.
... It has been reported that among the various surface modification processes, chemical modification of the fibers could help remove lignin, impurities, and waxes, improve adhesion, and improve the fiber/matrix interface (Huang et al. 2021;Ren et al. 2023). Furthermore, according to published results, the modification of straw with silane coupling agents plays a detrimental role in promoting the interfacial interaction between hydrophobic polymers and hydrophilic fibers (Daghigh et al. 2018;Sahai and Pardeshi 2019;Bahrami et al. 2021;Bahrami and Bagheri 2022). ...
... A significant increase in tensile strength (18.7%) was observed after incorporation of NaOH treated corn straw with chitosan/PLA as compared to the native corn straw based composite. In addition, based on the published results (Daghigh et al. 2018;Sahai and Pardeshi 2019;Bahrami et al. 2021;Bahrami and Bagheri 2022), the modification of lignocellulosic fibers with silane coupling agents plays a beneficial role in improving the interfacial interaction and covalent bonding between hydrophilic fibers and hydrophobic polymer matrix. The compatibility between the hydrophobic polymer matrix and the hydrophilic fiber of the composite can be improved, thus improving the mechanical strength of the composite. ...
In this study, an optimized composite was prepared based on chemically modified corn straw, chitosan, and poly(lactic acid) using Response Surface Methodology (RSM). The composite was produced by screw extruding and hot pressing. The Box Behnken Design (BBD) software was used to design the test to optimize the composite composition. The optimum ratio of 3 factors, e.g. chemically modified corn straw (0.10 to 0.40 g), chitosan (0.25 to 0.75 g), and poly(lactic acid) (2.00 to 3.00 g) on the response value (bending strength) of the composite was investigated. RSM-BBD provided the optimum combination of composites. The novel composite prepared under the optimized factors was characterized by Fourier transform infrared spectroscopy, mechanical testing, water absorption tests, contact angle tests, and scanning electron microscopy. The results showed that the mechanical strength, e.g., bending strength, impact strength, and tensile strength of chemically modified corn straw based composite were 21.6 MPa, 4.43 kJ/m2, and 20.0 MPa, respectively, which increased by 23.5%, 13.9%, and 18.7% compared to native corn straw based composite. Improved mechanical strength and hydrophobicity for chemically modified corn straw/chitosan/poly(lactic acid) demonstrated that chemically modified biomass fibers and bio-based degradable polymers have the potential to produce environmentally friendly composites.
... NaOH treatment removes a portion of impurities, lignin, hemicellulose, and waxes in lignocellulosic fibers to improve the interaction between biomass and high molecular polymer as well as to improve the mechanical performances (including strength and stiffness) of composite materials (Feng et al. 2020;Dixit et al. 2021). Based on the published results (Bahrami et al. 2021;Bahrami and Bagheri 2022), silane coupling agent played an important role in promoting covalent bonding between the hydrophobic polymer matrix and the fibers. The compatibility between the hydrophobic polymer matrix and the hydrophilic fiber as well as the strength of the composite can be improved. ...
A new class of bio-composites was developed by utilizing four kinds of lignocellulosic biomass fiber (bagasse, bamboo, rice husk, and rice straw) as filling fibers. Poly-β-hydroxybutyrate (PHB) and poly(butylene succinate) (PBS) in a mixture ratio of 7:3 were used as matrix materials with hot-press molding. The performance of the resulting composites was evaluated by compositional analyses, mechanical analysis, Fourier transform infrared (FTIR) spectroscopy, thermogravimetry, and morphological analysis. The interfacial adhesion, thermal stability, and comprehensive mechanical properties of the alkali treated bamboo/PHB/PBS composite were highest among the four bio-composites. The bending strength, tensile strength, and impact strength for alkali treated bamboo/PHB/PBS composite was 19.82 MPa, 12.97 MPa, and 4.30 kJ/m2, respectively. The thermal stability for NaOH modified bamboo/PHB/PBS composite was slightly superior to the other three composites, with the initial pyrolysis temperature of 248 °C, moderate pyrolysis speed, and the amount of pyrolysis residue (5.81%). The results showed the suitability of biomass fiber and biodegradable polymer for producing environmentally friendly composite materials.
... It has been reported that among different pretreatment process methods, NaOH treatment is a promising approach to remove hydrophobic extractives along with some lignin (Ge et al. 2020;Huerta-Cardoso et al. 2020). Additionally, according to published results, silanization is a crucial treatment to promote the compatibility and covalent bonding between hydrophilic fibers and hydrophobic polymer matrix as well as enhance composite strength (Bahrami et al. 2021;Bahrami and Bagheri 2022). Sugarcane bagasse is an important agro-industrial residue generated from sugarcane juice extraction. ...
... The absorbed hydrate molecules in swollen regions act as plasticizers and multiply the mobility of the cellulose chains. As some of the cementing material is removed during alkalization, the structure becomes less dense and the internal constraint was relieved (Cui et al. 2014, Dixit andYadav 2019;Bahrami et al. 2021). Furthermore, it was reported that alkali pretreatment can destroy the complex structure of lignocellulose materials, which is helpful for increasing the contact area between lignocellulose fiber and other materials as well as benefits for subsequent preparation process of composites (Mochane et al. 2021;Pei et al. 2022). ...
... According to the result of initial thermal-degradation temperature (273 °C), amount of pyrolysis residue (1.22%), and pyrolysis speed (Fig. 5b), it could be concluded that the thermal stability of NaOH-treated bagasse fiber/PBS/PLA composite was slightly higher than native bagasse fiber/PBS/PLA composite. It was reported that the alkaline treatment plays a crucial role in governing the ultimate properties of fibers and biocomposites (Bahrami et al. 2021). NaOH-treatment could remove part of hemicellulose (thermo-decomposed temperature from 230 to 310 °C) and lignin components (thermo-decomposed temperature from 300 to 400 °C) in bagasse fiber, which results in better thermal thermogravimetric stability. ...
Alkali-treated bagasse fiber was used as a process variable for optimization of the properties of polybutylene succinate/poly(lactic acid)-based biocomposites using Box-Behnken design (BBD) and response surface methodology (RSM). The optimum conditions for three factors, i.e., NaOH-treated bagasse fiber (0.55 to 1.65 g), polybutylene succinate (1.1 to 2.3 g), and poly(lactic acid) (2.2 to 3.4 g) on the bending strength of biocomposite were investigated. The optimum combination was 0.91 g of NaOH-treated bagasse fiber, 1.14 g of polybutylene succinate, and 3.10 g of poly(lactic acid). The bending strength for NaOH-treated bagasse fiber/polybutylene succinate/ poly(lactic acid) composite was 27.0 MPa, which was 26.0% higher than native bagasse fiber-based composite. The composites were also characterized by thermogravimetric analysis, mechanical testing, Fourier transform infrared, scanning electron microscopy, water absorption, and contact angle tests. Results demonstrated that the bending strength, impact strength, and tensile strength of alkali treated bagasse fiber-based biocomposite increased by 26.0%, 15.5%, and 23.3%, separately, compared with native bagasse-based composite after sequential homogenization, compounding, and hot pressing. The hydrophobicity for alkali-treated bagasse fiber/PBS/PLA was also improved. Thus, NaOH-treated biomass materials/biodegradable polymer was judged to be suitable for preparing green composite materials.
... Water evaporated from all fibers between 30 and 145ºC, hemicellulose and cellulose degraded from 220 to 350ºC and 250 -460ºC respectively while lignin decomposed between 140 and 300ºC and 435 -610ºC. These values are within the range disclosed by other researchers (Chilukoti et al., 2022;Moumakwa et al., 2021;Soni and Sinha, 2022;Bahrami et al., 2021;da Silveira et al., 2022;Guo et al., 2019;Hajiha et al., 2014;Jiang et al., 2018b;Silva et al., 2021;Sirghie et al., 2015;Xiang et al., 2021). Flax fibers were slightly affected by HTTCs and exhibited slight mass loss differences with increasing HTTCs. ...
... A constant cellulose degradation peak at 375ºC was maintained as HTTCs increased as seen in the DTG of flax fibers. This maximum cellulose peak is close to 350ºC (Bahrami et al., 2021;Makhlouf et al., 2022); 351ºC (Sirghie et al., 2015) and 385.5ºC (Xiang et al., 2021) reported in literature. DSC indicates a change in the reactivity of flax fibers with increased HTTCs. ...
... The C--C aromatic ring skeletal vibration groups in lignin at 1585 cm − 1 (Moumakwa et al., 2021;Mukhtar et al., 2018;Soni and Sinha, 2022;da Silveira et al., 2022;Guo et al., 2019;Silva et al., 2021;Abdul Razab et al., 2021;Ishak et al., 2013;Heckadka et al., 2022;Titok et al., 2010) increased in hemp and palm fibers but remained unchanged in flax fibers. The wavelength at 1737 cm − 1 is related to xylan C--O unconjugated stretching indicating the presence of ketones and aldehydes in carboxylic groups of cellulose and hemicellulose (Jin et al., 2021;Jiang et al., 2018a;Guo et al., 2019;Alemdar and Sain, 2008;Hult et al., 2003) or carbonyl group of hemicellulose (Bahrami et al., 2021;Sirghie et al., 2015;Xiang et al., 2021;Makhlouf et al., 2022;Heckadka et al., 2022;Arbelaiz et al., 2006;Kirubakaran et al., 2022) or either acetyl and uronic ester groups of hemicellulose or ester linkage of carboxylic group of ferulic and p-coumeric acids of lignin and/or hemicelluloses (Alemdar and Sain, 2008). A reduced band is seen in flax and hemp fibers while palm fibers showed no variation. ...
There is an increasing interest in using natural fibers to replace synthetic fibers in fiber cement composites.
However, the hydrophilicity and geometric instability of natural fibers undermines their suitability for this
purpose. A potential solution is to apply hydrothermal treatment to modify the natural fibers before use.
However, the efficacy of this treatment on all natural fibers is still unclear. This research investigated the influence of hydrothermal treatment cycles on three natural (plant) fibers and the resulting performance when
used in fiber cement composites. African oil palm (Elaeis guineensis) mesocarp fibers and bast fibers sourced from
hemp (Cannabis sativa) and flax (Linum usitatissimum) plants were used. These fibers were subjected to six hydrothermal treatment cycles and assessed for tensile strength, vapor sorptivity, chemical and morphological
differences. Both untreated and hydrothermally treated fibers were incorporated in fiber cement composites of
varying compositions and characterized for flexural strength, porosity and mineralogical phases. The treatment
affected the fibers differently depending on their composition. It enhanced fibers with high cellulose, low ketones
and organic matter contents and was found to be milder on flax fibers than hemp and palm fibers. Dynamic vapor
sorption time on treated fibers decreased by 1 hour 11 minutes, 4 hours 15 minutes and 5 hours 55 minutes in
flax, hemp and palm fibers respectively. The cellulose decomposition peak was maintained at 375ºC in flax fibers
but shifted from 330 to 375ºC in hemp fibers and 350 – 375ºC in palm fibers. FTIR peak ratios revealed that flax
fibers lost lignin and hemicellulose proportionally while lignin degraded the most in palm fibers and hemicellulose in hemp fibers. The treatment enhanced the crystallinity of flax fibers better than hemp fibers but depleted
the crystallinity of palm fibers. Flax and hemp fibers had increased tensile strength and improved the performance of fiber cement composites with hydrothermal treatment while palm fibers did not. Generally, hydrothermally treated flax and hemp fibers increased the specific energy (SE) by 6 – 24% and 2 – 19% respectively
while palm fibers showed a decrease in SE by 20%. An enhanced bridging ability was exhibited by the treated
hemp and flax fibers compared to their untreated fibers. The amorphous matrices of fiber cement composites
with fly ash and crystalline matrices of fiber cement composites with palm oil fuel ash performed comparably
well with flax and hemp fibers as reinforcement. The use of palm oil fuel ash in fiber cement composites offered
greater resistance to fiber pull out and had a greater modulus of rupture (MOR) than those with fly ash. This
resulted in untreated fibers performing better in fiber cement composites with palm oil fuel ash while treated
fibers performed best in those with fly ash. Overall, hydrothermal treatment was an efficient means of enhancing
the performances of fibers with high cellulose, low ketones and organic matter as reinforcement for fiber cement
composites.
... To improve the suitability of flax fibers for use in composites, they were firstly alkali-treated based on an optimal protocol from our previous study. 17 The fibers were exposed to a dilute aqueous solution of 5% (w/v) NaOH with liquor to fiber ratio of 10. Alkalization proceeded for 30 min at room temperature. ...
... Also, the 10-20 μm diameter of fibers in Figure 11(c) indicates that the alkali modification, extrusion, and injection molding processes have effectively separated elementary flax fibers from their technical bundles of 100-200 μm diameters. 17 Besides, the large number of holes and protruding fibers of considerable length manifests that fiber ends broke loose from the matrix, whereas the remainder of the material kept its integrity. The smooth and clean surface of fibers, along with the gaps observed in the interface, evidence that a strong bonding was not established between the fibers and matrix allowing the fibers to be extensively pulled out at the crack wake via a brittle fracture at their interface. ...
Nowadays, the significance of sustainability has urged composite manufacturers to replace traditional synthetic fibers with eco-friendly natural alternatives due to their environmental and economic benefits. This work aims to fabricate hybrid polypropylene (PP) composites with short flax fibers, octene-ethylene copolymer (POE) rubber particles, and maleic anhydride-grafted polypropylene (MAPP) compatibilizer. The main goal is to gain an insight into the combined effect of toughening mechanisms induced by the short fibers and rubber particles at the crack tip and wake of composites, which is a crucial step in reaching a balance between toughness and rigidity. In this regard, a novel microscopy strategy is taken to elucidate the operating mechanisms at the crack tip and crack wake of composites. Also, differential scanning calorimetry (DSC), tensile, and Charpy impact tests were employed to investigate the effect of hybridization on the crystallization behavior, tensile, and impact properties of composites. The experimental results showed that the combined effect of encouraging matrix plastic deformation and synergistic work of toughening mechanisms at the crack tip and wake in the MAPP-modified hybrid composites containing 30% flax fibers and 10% POE rubber particles yielded an optimal improvement of 315%, 135%, and 37% in impact strength, elastic modulus, and ultimate tensile strength, respectively, over the neat PP formulation.
... Chemical treatment, such as alkali treatment, must be used to modify the fibersurface in order to establish better bonding between matrix and reinforcement. A lot of research was carried out to attain better mechanical properties by fiber alteration [7][8][9]. ...
Natural fiber polymer composites are gaining enormous attention in the modern era due to their economical, renewable, biodegradable, and better mechanical characteristics. In this work an attempt is made on the development of pomegranatepeel powder-filled jute fiber epoxy composites. The polymer composites are prepared by hand layup process. The wasted pomegranatepeel was utilised and used as filler for the preparation of composite. The hybrid composites were prepared by reinforcement of jute fiber at a constant 20 wt% and distinctpomegranatepeel powder filler wt % (2, 4, 6, and 8). The mechanical propertiessuch as impact, flexural, and tensile strength studies were performed.There were an enhancement in impact, flexural, and tensile strengths when pomegranate peel powder filler was added up to 6 wt%, but beyond that wt.%, agglomeration occurred, resulting in a decrease of that a loss of mechanical properties.
Biopolymers and bio‐fillers derived from natural, organic, and abundant resources have garnered more responsiveness owing to their affordability and degradability in the production of packaging plastics. This study explores the novel use of different proportions (5%, 10%, 15%, and 20%) of 5% alkali‐treated Putranjiva roxburghii seed shell filler (PRSSF) as a bio‐filler in combination with polyvinyl alcohol (PVA) for the first time. FTIR analysis showed the creation of robust hydrogen bonds and enhanced compatibility between the matrix and the alkalized PRSSF. The XRD results revealed that alkalized PRSSF strengthens the structural integrity of biofilms. The water absorption of the PVA/at PRSSF biofilm samples decreased by 88.38% at a higher composition (20%) of alkali‐treated PRSSF due to their alkalized hydrophobic filler. Due to the effect of at‐PRSSF into PVA, the resulting films demonstrated a degradation temperature and char residue of 334.8°C and 13.57%, respectively, and relatively better UV‐barrier properties in a range of visible light. When compared with pure PVA films, the tensile strength and corresponding modulus of PVA/20% at‐PRSSF films increased by 32.94% and 16.2%, respectively. Therefore, the PVA/at‐PRSSF biofilms produced in this study are ideal materials for wrapping and folding applications.
Highlights
PVA/at‐PRSSF films outperform in multiple aspects as compared with pure PVA.
Tensile strength of PVA/20%‐PRSSF films increased by 32.94%.
Elongation at break decreased with at‐PRSSF loading.
Water absorption in PVA/20% PRSSF biofilm decreased by 88.38%.
Fractography showed voids and agglomerations at high filler levels.
