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Photographs of lignocellulosic fibers from green coconut: (a) bunch of fibers with different diameters; and (b) single fiber for measuring the diameter
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The growing consumption of tender coconut water in Brazil has resulted in a generation of green husk, which in turn has led to pollution, as it takes eight to ten years to degrade. With the objective of finding applications for these fibers, the characterization of their chemical composition, tensile properties, and structural properties is present...
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Context 1
... diameter and length of natural fibers, such as green coconut fibers, are relevant parameters to their applications, especially in the development of polymer-based composites, where they are used as reinforcement. Figure 1a shows a photograph of green coconut fibers with different diameters and lengths, while Fig. 1b is a photograph of a single fiber showing the non-uniformity along the length of the fiber. The diameter of the fiber tapered from one end to the other, as can be seen from the values listed in Table 1. ...
Context 2
... diameter and length of natural fibers, such as green coconut fibers, are relevant parameters to their applications, especially in the development of polymer-based composites, where they are used as reinforcement. Figure 1a shows a photograph of green coconut fibers with different diameters and lengths, while Fig. 1b is a photograph of a single fiber showing the non-uniformity along the length of the fiber. The diameter of the fiber tapered from one end to the other, as can be seen from the values listed in Table 1. This is understandable because the green coconut fibers can be divided into fine, medium, and thick and the most resistant fibers are ...
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This work is focused on development of hybrid composites with better toughness and hardness by including natural filler reinforcements. The changes in the behavior of the composite due to filler inclusion were evaluated through acoustic emission technique to reveal the mechanism behind the improvement in properties. The hybrid composite was develop...
Citations
... Coir fibres can be classified into two main categories based on the age of the coconut, namely mature and immature fibres, where immature fibres are relatively raw and softer than stiff mature fibres [11]. Mature fibres, also known as brown coir, are harvested after the coconut is ripe, whereas immature fibres are extracted from green coconuts. ...
... Figure 10 summarizes the effect of fibre treatment on its failure strain. Though the mature fibres showed a relatively higher strength, the immature fibres possessed higher failure strain, as observed by many researchers [11,63]; the average difference observed in the failure strains between immature and mature fibres was 23%. This is due to the higher lignin content in mature fibres than in the immature, which imparts rigidity. ...
Coconut fibres have recently been used in numerous civil engineering applications, mostly in pavement structures as geotextiles. However, their performance is usually lower than the elements made with synthetic fibres, primarily due to their inherent variable characteristics, which mostly depend on the maturity level and pre-processing of the fibres. In this study, an effort is made to develop a framework for enhancing the characteristics of coir, considering the age of the fibres (immature and mature) as well as the treatment techniques. The treatment methods such as washing and boiling; alkali treatment with sodium hydroxide (NaOH), potassium hydroxide (KOH) and calcium hydroxide (Ca(OH)2); acidic treatment with acetic acid (CH3COOH); and grafting with methyl methacrylate (MMA) were optimised for their concentration and soaking duration. The washing of the fibres generally results in a slight reduction in the diameter of the fibres due to the removal of surface impurities. Further, during the chemical treatments (NaOH and Ca(OH)2), the particles get deposited on the fibres, resulting in improved absolute density. Thus, the reduction in diameter and the increase in absolute density of the fibres after the treatment process results in improved mechanical characteristics. The results indicated a superiority of chemical treatments over physical methods and grafting techniques. Post alkali treatment with Ca(OH)2, unwashed mature and immature fibres demonstrated a 40.5% and 40.3% increase in tensile strength, while the treatment with NaOH resulted in an increase in the failure strain by 53% and 18%, respectively, under optimised conditions compared to unwashed fibres. Treatment with Ca(OH)2 demonstrated higher tensile strength under optimised conditions; however, beyond the optimised treatment duration, a drastic reduction in the strength was observed, whereas NaOH-treated fibres exhibited a gradual decrease in the tensile strength. Though alkali treatments could enhance the properties of coir fibres, an excessive concentration or soaking duration was found to affect the fibres’ physical and mechanical characteristics adversely. For mature fibres, the optimum parameters (strength and failure strain) were obtained for 5% concentration of NaOH solution with a soaking period of 5 h, while for immature fibres, 6 h soaking duration was found to be optimum. Based on this comprehensive study, a framework is proposed which could be readily adopted for enhancing the quality of coir fibres.
... Currently, the use of these fibers is being mainly intended for use in different sectors such as agriculture, mattress manufacturing, brushes, fishing nets, carpets, among others. Despite the different applications, coconut fibers are considered a by-product of the agricultural industry due to their excessive production and ineffective waste management procedures (Lomelí-Ramírez et al., 2018Oluwole et al., 2022. ...
... The moisture content of the husk can in turn affect the mechanical properties of the coconut fibers. Studies have reported that green coconut fiber has low tensile properties(Lomelí-Ramírez et al., 2018). Moreover,Terdwongworakul et al. (2009) reported a high rupture force for green coconuts compared to the brown fibers. ...
Coconut husk is widely used as a source of natural fibers in the tropics. Dehusking and fiber extraction are some of the important unit operations in coir manufacturing. For the development of an efficient and economically viable fiber extraction machine, the engineering properties of conventional and organically grown coconuts were evaluated. Selected engineering properties of whole coconut were investigated. The average true density and bulk density were in the range of 414.63 ± 111.85 to 529.28 ± 123.02 and 161.66 ± 24.41 to 212.23 ± 18.96 kg/m³, respectively. Along with whole coconuts, engineering properties of husk (weight, moisture content, and husk thickness), shell (weight, thickness, bulk density, and moisture content), and kernel parameters (weight, thickness, and moisture content) were also evaluated. The application of organic treatment (T4) exhibited substantial impacts, leading to a higher coconut weight (1.354 kg) as compared to conventional practices (T5), and increased dimensions (158.599 mm diameter and 205.000 mm height) and improved bulk density (190.97 kg/m³) in comparison to other organic treatments. In deshelled coconuts, T4 showcased a higher shell weight (175.667 g) and shell thickness (4.767 mm). The kernel parameters of T4 displayed enhancements, featuring a kernel weight of 314.334 g and a thickness of 11.774 mm. Although the study could not find any correlation between the farming practices and engineering characteristics of coconut fruit, the data presented herein could be utilized for the design and improvisation of efficient fiber extraction machines.
Practical Applications
Developing countries are exploring the possibilities of implementation of organic farming for the production of agro products. Implementation of organic farming not only affects yield but may also change the engineering properties and nutritional characteristics of products. Understanding the engineering properties of food products grown under organic conditions is important for the modification of the design in the existing machineries and/or development of new food processing equipments.
... The lignin content in the plain CF in this study was determined to be 22%. This result contrasts with findings by Souza et al. [53], Pereira et al. [54], and Lomelí-Ramírez [55], who reported higher lignin values at 30%, 31%, and 35%, respectively. ...
The incorporation of natural lignocellulosic fibers as reinforcements in polymer composites has witnessed significant growth due to their biodegradability, cost-effectiveness, and mechanical properties. This study aims to evaluate castor-oil-based polyurethane (COPU), incorporating different contents of coconut coir fibers, 5, 10, and 15 wt%. The investigation includes analysis of the physical, mechanical, and microstructural properties of these composites. Additionally, this study evaluates the influence of hydrothermal treatment on the fibers, conducted at 120 °C and 98 kPa for 30 min, on the biocomposites’ properties. Both coir fibers (CFs) and hydrothermal-treated coir fibers (HTCFs) were subjected to comprehensive characterization, including lignocellulosic composition analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The biocomposites were subjected to water absorption analysis, bending tests, XRD, SEM, FTIR, and TGA. The results indicate that the 30 min hydrothermal treatment reduces the extractive content, enhancing the interfacial adhesion between the fiber and the matrix, as evidenced by SEM. Notably, the composite containing 5 wt% CF exhibits a reduced water absorption, approaching the level observed in pure COPU. The inclusion of 15 wt% HTCF results in a remarkable improvement in the composite’s flexural strength (100%), elastic modulus (98%), and toughness (280%) compared to neat COPU. TGA highlights that incorporating CFs into the COPU matrix enhances the material’s thermal stability, allowing it to withstand temperatures of up to 500 °C. These findings underscore the potential of CFs as a ductile, lightweight, and cost-effective reinforcement in COPU matrix biocomposites, particularly for engineering applications.
... However, the development of the coconut plantation sector has generated excessive and significant biomass waste in the country. This waste, which includes coconut husks, shells, empty bunches, and fronds, is normally discarded on embankments and left in an open environment [24]. This will result in waste accumulation and, consequently, soil contamination and pest infestation. ...
Lactic acid is a versatile chemical with a wide range of industrial applications, including food additives as well as the production of biodegradable plastics, pharmaceuticals and cosmetics. LA can be produced through carbohydrate fermentation using various microorganisms, including lactic acid bacteria (LAB). However, the high production cost of commercial fermentation media for lactic acid raises concerns among researchers. Consequently, there is a demand for research to develop new, more affordable, and sustainable fermentation media. Utilizing underutilized agro-industrial wastes from Malaysia, particularly in the coconut, oil palm, rice, and sugarcane processing industries, offers several advantages. These include biomass reuse, cost-effective production of valuable chemicals, and agricultural waste reduction. This review discusses the potential of underutilized Malaysian agro-industrial waste from the coconut, oil palm, rice and sugarcane processing industries as sustainable carbon sources for LA production. The topics covered encompass the chemical and nutritional composition of the wastes, their potential for lactic acid fermentation with specific microorganisms, factors influencing lactic acid production, and potential applications. Additionally, this review also highlights the challenges and opportunities associated with reutilizing agricultural waste for lactic acid production.
... This implies that the Philippines have an abundant supply of coconut husk that can be used as a raw material for nanocellulose production. A study have reported that there are variation in the properties of coconut fibers depending on age and locality [12]. Thus, the aim of this study is to extract nanocellulose from matured coconut husk grown in the Philippines. ...
... The results of the analysis is shown in Table 2. Based on Table 2, the largest component of matured coconut husk is lignin which is higher but comparable with those reported by studies using brown fibers (31.04-44.06%) [10,11] and green coconut husk fibers (35.46-48%) [12,13,14]. Alphacellulose is the second largest component which is the vital component for the extraction of nanocellulose. ...
Nanocellulose is a promising nanomaterial that can be used in various applications such as reinforcements for composite films. Agricultural lignocellulosic wastes, such as coconut husks, offer great advantages as raw materials for nanocellulose extraction due to their abundance and economic viability. The aim of this study is to extract nanocellulose from matured coconut husk. Nanocellulose was extracted using sulfuric acid hydrolysis and characterized using Atomic Force Microscopy (AFM). Results showed that nanocellulose extracted from matured coconut husk has 2.26% yield with agglomerated, rod-shaped structures. An average aspect ratio of 3.16 ± 1.82 nm was also obtained.
... fiber volume fraction. The negligible differences resulted from the low specific gravity of kenaf, coconut, and synthetic fibers [55][56][57]. Additionally, the difference in thickness along the length of the fibers caused differences in volumetric quantity and their ability to occupy space in the mortar matrix [42]. ...
... fiber volume fraction. The negligible differences resulted from the low specific gravity of kenaf, coconut, and synthetic fibers [55][56][57]. Additionally, Fibers 2023, 11, 9 8 of 14 the difference in thickness along the length of the fibers caused differences in volumetric quantity and their ability to occupy space in the mortar matrix [42]. ...
The global market for tires is ever-growing, and partially replacing sand with crumb rubber (CR) as fine aggregates in concrete could reduce environmental pollution. However, the main barrier to the complete usage of recycled tire crumbs in construction is the deterioration effect of CR on the mechanical properties of cement-based composites. Therefore, this paper attempts to improve the fresh and hardened properties of crumb rubber mortar (CRM) by incorporating polypropylene-polyethylene synthetic fibers with coconut and kenaf natural fibers as reinforcements. A total of 18 mix designs were developed with varying fiber combinations and rubber crumb replacement. Subsequently, parametric studies with chemical admixture were conducted at 3, 7, and 28 days to improve the flowability and resulting mechanical properties of the fiber-reinforced CRM. According to the results, the single and hybrid fibers positively improved the mechanical properties of cement mortar at 5-15% CR replacement. It can be concluded that adding single and hybrid fibers enhanced the performance of cement mortar modified with tire crumb rubber aggregates by providing varying degrees of improvement.
... Among this variety of morphologies, some characteristic rod-like structures with regular porosity were identified (Fig. 5D-F). In particular, these structures showed a surface with small wells at regular intervals, which is a characteristic plant cell structure, as the one included in the SEM image of Fig. 5L [61,62]. The highly porous structure of peanut shells is widely known and is usually exploded to prepare adsorbents for pollutants removal from water [63][64][65]. ...
Mild acid hydrolysis of various plant residues has been proposed in recent years as a novel way of transforming biomass into bioplastics. However, the alkaline hydrolysis of such residues has not yet been studied for this purpose. In this work, an in-depth comparative study is carried out for the first time on the physicochemical, thermal, mechanical, and morphological aspects of the bioplastics produced by acid and alkaline hydrolysis starting from two different plant residues: spinach stems (SS) and peanut shells (PS). The chemical treatments followed here, produced self-standing SS bioplastics and hydrolyzed PS powders that were incorporated as fillers in a thermoplastic starch (TPS) matrix to obtain composites. The alkaline hydrolysis led to bioplastics with superior mechanical and barrier properties than those obtained from acid hydrolyzed biomass. The Young's modulus (YM) of SS-bioplastics produced upon alkaline hydrolysis, tripled, their tensile strength (TS) almost doubled, and their water vapor permeability (WVP) was reduced by 15%, compared to SS-bioplastics produced upon acidic hydrolysis. TPS-alkali hydrolyzed PS composites showed increments of 22% in YM, 10% in TS, and a reduction of about 30% in their WVP compared to the respective acid hydrolyzed composites. The physicochemical, thermal, and morphological analysis confirmed that the main cause of these improvements was cellulose nanofibrillation, which was favored by the greater efficiency of the alkaline medium to hydrolyze the pectin, hemicellulose, and lignin polymers. This research represents a step ahead in understanding the processes of transforming non-edible vegetable wastes into sustainable bioplastics and comes in a critical moment when an urgent transition towards a circular economy is need, and industrial processes are expected to reduce their carbon footprint and generate zero waste.
... So-called developing countries are mainly found in tropical and subtropical climatic regions, where coconut palms and bamboo ( Figure 1) are the most widely grown natural fiber plants [20,[25][26][27]. The cultivation of coconut palms in coastal regions is associated with lower freshwater requirements due to their high saltwater tolerance [20,28], but the coir obtained from coconuts has comparatively low mechanical properties in comparison to the other plant fibers (Table 1). Bamboo offers many advantages as a plant fiber source due to its early harvest maturity after 3 to 5 years [29,30], simple harvesting and processing, vegetative reproduction via rhizomes [31], protection of the soil from erosion [32], and positive influence on the water table [12]. ...
Natural plant fibers represent a sustainable alternative to conventional fiber reinforcement materials in cementitious materials due to their suitable mechanical properties, cost-effective availability and principle carbon neutrality. Due to its high tensile strength and stiffness as well as its worldwide distribution along with rapid growth, bamboo offers itself in particular as a plant fiber source. In experimental studies on concrete beams reinforced with plant fibers, a positive influence of the fibers on the flexural behavior was observed. However, the load-bearing effect of the fibers was limited by the poor bond, which can be attributed, among other things, to the swelling behavior of the fibers. In addition, the plant fibers degrade in the alkaline environment of many cementitious building materials. In order to improve the bond and to limit the alkalinity and to increase the durability, the use of ultra-high performance concrete (UHPC) offers itself. Since no tests have been carried out, investigations on the flexural behavior of UHPC with bamboo fibers were carried out at the Institute of Concrete Construction of Leibniz University Hannover. The test results show a significantly improved load-bearing behavior of the fibers and the enormous potential of the combination of UHPC and bamboo fibers.
... Before designing the machine, a tensile test of coconut fiber was carried out using a universal material testing machine (Lomelí-Ramírez et al., 2018). The tensile strength of coconut fiber was measured until all samples were broken. ...
Manual stripping of coconut fiber has low processing efficiency coupled with difficulty in operation. To overcome these problems, a coconut fiber bionic‐stripping device based on Lucanidae palate frictional characteristics was designed. The device relied on the torsion spring edge hook and brush working principle to strip the coconut fiber. The coconut shell was not damaged during the stripping operation owing to the elasticity and toughness of the bionic torsional spring. The test parameter optimization was carried out using the coconut fiber bionic‐stripping device and analyzed using Design‐Expert.V8.0.6 Software. The results showed that the planting distance between torsion springs had significant effect on stripping coconut fiber (p < .001), but the diameter of torsion spring had the least effect on stripping coconut fiber. Regression analysis of the test data showed that the device had higher processing efficiency at coconut rotation speed of 1200 rad/min, coupled with bionic torsion springs diameter and planting distance of 2.0 and 17 mm, respectively. Under optimal combination of parameters, coconut fiber removal thickness was found to be R△ = 30.9 mm. The data obtained showed high repeatability, thereby indicating that the coconut fiber bionic‐stripping device can meet the technological requirements for coconut fiber removal.
Practical Applications
This study focuses on coconut characteristics as well as the process requirements for coconut fiber removal. A mechanism to strip the fiber using bionic torsion springs was proposed, which was designed based on the characteristics of the Lucanidae palate. Including a device for peeling coconut fiber using bionic torsion springs. Furthermore, the structural stress analysis of the device was carried out so as to explore the feasibility of using the bionic torsion spring group to peel coconut fiber. Parameter optimization test, performance analysis, and comparative performance analysis were carried out using the device to analyze the influence of different bionic torsion spring group parameters on the thickness of stripped coconut fiber. This can provide a theoretical and experimental basis for the study of coconut fiber stripping mechanism, and can broaden the existing research methods of coconut fiber stripping.
