A Comprehensive Review on Natural Fibers: Technological and Socio-Economical Aspects

Spinning the Future: The Convergence of Nanofiber Technologies and Yarn Fabrication

The rapid advancement in nanofiber technologies has revolutionized the domain of yarn materials, marking a significant leap in textile technology. This review dissects the nexus between cutting-edge nanofiber technologies and yarn manufacturing, aiming to illuminate the pathway toward engineering advanced textiles with unparalleled functionality. It first discusses the fundamentals of nanofiber assemblies and spinning techniques, primarily focusing on electrospinning, centrifugal spinning, and blow spinning. Additionally, the study delves into integrating nanofiber spinning technologies with traditional and modern yarn fabrication principles, elucidating the design principles that underlie the creation of yarns incorporating nanofibers. Twisting technologies are explored to examine how they can be optimized and adapted for incorporating nanofibers, thus enabling the production of innovative nanofiber-based yarns. Special attention is given to scalable strategies like centrifugal and blow spinning, which are spotlighted for their efficiency and scalability in fabricating nanofiber yarns. This review further analyses recently developed nanofiber yarn applications, including wearable sensors, biomedical devices, moisture management textiles, and energy harvesting and storage devices. We finally present a forward-looking perspective to address unresolved issues in nanofiber-based yarn technologies.

Era of bast fibers-based polymer composites for replacement of man-made fibers

Bast fibers are defined as those obtained from the outer cell layers of the bast of various plant families. They are finding use in textile applications and are widely used as reinforcements for green composites, as bast fibers are perceived as "sustainable". There is a growing demand for bast fibers across the world due to their renewable and biodegradable nature. The bast fibers are mainly composed of cellulose, which potentially considers the growing techniques, harvesting and extraction processes of bast fibers most used to produce fibers with appropriate quality to apply in the daily lives of modern men and women in contemporary society. This review paper looks at many aspects of natural fibers, with a focus on plant bast fibers, including their impact on prehistoric and historical society. This review shows that bast fibers are competitive compared to man-made fibers in many applications, but variability in mechanical properties and low tenacity may limit their use in high-strengthh composites and extend to, particularly in aerospace, automotive, packaging, building industries, insulation, E-composites (Eco composites), geotextiles and many other applications are currently being explored. Considering, important characteristics of bast fibers include physical, mechanical, and chemical properties. This makes bast fibers one of the most important classes of plant fibers to use as reinforcing agents in thermosetting/thermoplastic polymer matrices. And the effect of bast fibers as reinforcement in the properties of ECO-composites, GREEN-composites, BIO-composites, lightweight composites. Bast fibers play an important role in sustainability, the preservation of the health of the environment, the well-being of the next generation, and even the daily lives of men and women in the contemporary world.

Flame Retardancy of Short Flax Fibers Modified by Radiation-Induced Grafting of Phosphonated Monomers: Comparison between Pre- and Simultaneous Irradiation Grafting

Short flax fibers have been modified by radiation-induced grafting using methacrylate monomers containing phosphorus to give them a flame-retardant character. Two methodologies, namely pre-irradiation and simultaneous irradiation grafting, were examined. Certain parameters, notably the dose and the irradiation source (e-Beam and γ rays), were evaluated. The grafting efficiency, in terms of phosphorus content (mass percentage), was measured by X-ray fluorescence spectrometry (XRF). Using simultaneous irradiation, 2.39 wt% phosphorus could be obtained from 10 kGy, compared to 100 kGy in pre-irradiation. Furthermore, for similar phosphorus levels, the location of the grafted polymer chains was different for the two methodologies. The effect of phosphorus content on thermal properties and fire behavior was evaluated on a microscopic scale using a pyrolytic flow combustion calorimeter (PCFC) and on a laboratory scale using a cone calorimeter. It was then pointed out that flammability was linked to the phosphorus content and likely its location, which is associated with the radiation-induced grafting methodology, showing that the grafting conditions influence the final fire properties. Simultaneous irradiation, thus, proved to be more interesting in terms of efficiency and final properties.

Simulation of a Composite with a Polyhydroxybutyrate (PHB) Matrix Reinforced with Cylindrical Inclusions: Prediction of Mechanical Properties

Biocomposite development, as a sustainable alternative to fossil-derived materials with diverse industrial applications, requires expediting the design process and reducing production costs. Simulation methods offer a solution to these challenges. The main aspects to consider in simulating composite materials successfully include accurately representing microstructure geometry, carefully selecting mesh elements, establishing appropriate boundary conditions representing system forces, utilizing an efficient numerical method to accelerate simulations, and incorporating statistical tools like experimental designs and re-regression models. This study proposes a comprehensive methodology encompassing these aspects. We present the simulation using a numerical homogenization technique based on FEM to analyze the mechanical behavior of a composite material of a polyhydroxybutyrate (PHB) biodegradable matrix reinforced with cylindrical inclusions of flax and kenab. Here, the representative volume element (RVE) considered the geometry, and the numerical homogenization method (NHM) calculated the macro-mechanical behavior of composites. The results were validated using the asymptotic homogenization method (AHM) and experimental data, with error estimations of 0.0019% and 7%, respectively. This model is valuable for predicting longitudinal and transverse elastic moduli, shear modulus, and Poisson's coefficient, emphasizing its significance in composite materials research.

Extraction and characterization of a newly developed cellulose enriched sustainable natural fiber from the epidermis of Mikania micrantha

Riding on the journey of a sustainable world it is very crucial to extend the usage of natural cellulosic fiber from renewable sources. Due to their numerous applications and eco-friendly behavior, natural cellulosic fibers are in greater demand every day. In this article a new natural fiber extracted from the creepers of Mikania micrantha with the help of 5% NaOH retting process. Previously no research work have been done with this fiber. The fiber was characterized by following ASTM D1909, ASTM D 2654, ASTM D1445, TAPPI standard for determination of moisture regain and content, bundle fiber strength and chemical composition respectively. XRD, SEM, FTIR and TGA analysis were also done for the identification of crystallinity, fiber morphology, functional group and thermal behavior. The tests results showed that it is a cellulose enriched textile fiber having 56.42% cellulose. The average moisture regain and content % were 9.17% and 8.4% respectively analyzed from the five samples. The average tenacity was determined 38.6 gm/tex with 1.8% elongation and the crystallinity of the tested fiber was 72%. The maximum degradation temperature for this fiber was 477 °C. The application of this noble fiber can be for making fiber reinforced composites, cellulose nanomaterials, biomaterials etc.

Tensile Strength Improvements of Ramie Fiber Threads through Combination of Citric Acid and Sodium Hypophosphite Cross-Linking

Ramie (Boehmeria nivea) is believed to be one of the strongest natural fibers, but it still remains behind synthetic materials in terms of tensile strength. In this study, ramie materials were prepared to evaluate the modification crosslinking effect of natural fiber. The aim is to optimize various concentrations of citric acid (CA) crosslinking by adding Sodium hypophosphite (NaPO2H2), which is activated at different temperatures, to obtain the highest tensile mechanical strength. This crosslinking effect has been confirmed by FTIR to show the esterification process in the molecular structure of cellulose. The changes in the character of the fiber surface were analyzed by SEM. The tensile strength increased from 62.33 MPa for 0% CA to 124-172.86 MPa for decorticated fiber with a CA concentration of 0.75-1.875% (w/w). A significant increase in tensile strength was observed more than 19 times when CA/SHP 1% was treated at an activation temperature of 110 °C with a superior tensile strength of 1290.63. The fiber crosslinked with CA/SHP should be recommended for application of Natural Fiber Reinforced Polymer Composite (NFRPC), which has the potential to use in functional textile and industrial sector automotive or construction.

Effect of Plant Fiber on Early Properties of Geopolymer

Geopolymer (GP) is environmentally friendly, has good mechanical properties and long-term workability, and has broad application prospects. However, due to the poor tensile strength and toughness of GPs, they are sensitive to microcracks, which limits their application in engineering. Fiber can be added to GPs to limit the growth of cracks and enhance the toughness of the GP. Plant fiber (PF) is cheap, easy to obtain, and abundant in source, which can be added to GP to improve the properties of composites. This paper reviews recent studies on the early properties of plant fiber-reinforced geopolymers (PFRGs). In this manuscript, the properties of PFs commonly used for GP reinforcements are summarized. The early properties of PFRGs were reviewed, including the rheological properties of fresh GPs, the early strength of PFRGs, and the early shrinkage and deformation properties of PFRGs. At the same time, the action mechanism and influencing factors of PFRGs are also introduced. Based on the comprehensive analysis of the early properties of PFRGs, the adverse effects of PFs on the early properties of GPs and the solutions were summarized.

Pretreatment with dilute maleic acid enhances the enzymatic digestibility of sugarcane bagasse and oil palm empty fruit bunch fiber

Lignocellulose is resistant to degradation and requires pretreatment before hydrolytic enzymes can release fermentable sugars. Sulfuric acid has been widely used for biomass pretreatment, but high amount of degradation products usually occurred when using this method. To enhance accessibility to cellulose, we studied the performances of several dilute organic acid pretreatments of sugarcane bagasse and oil palm empty fruit bunch fiber. The results revealed that pretreatment with maleic acid yields the highest xylose and glucose release among other organic acids. The effects of concentration, duration of heating and heating temperature were further studied. Dilute maleic acid 1 % (w/w) pretreatment at 180 °C was the key to its viability as a substitute for sulfuric acid. Moreover, maleic acid did not seem to highly promote the formation of either furfural or 5-HMF in the liquid hydrolysate after pretreatment.

Complex Effects of Hemp Fibers and Impact Modifiers in Multiphase Polypropylene Systems

Natural fibers-reinforced polymer composites have progressed rapidly due to their undeniable advantages. Most of the commercial polypropylene (PP)-based materials are characterized by either high impact toughness or high stiffness, while the manufacture of PP composites with both good toughness and stiffness is challenging at present. In this work, poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) and poly(styrene-b-butadiene-b-styrene) (SBS) copolymers were used in different amounts as modifiers in PP/hemp fibers (HF) composites, with the aim to use them for electrical vehicle parts. The interface in these multiphase systems was controlled by the addition of maleated polypropylene (MAPP). SEBS and SBS showed different effects on the elongation at break of the blends and the corresponding composites due to the HF that stiffened the multiphase systems. Similarly, a different action of MAPP was observed in the composites containing SEBS or SBS: higher Young's and storage moduli were obtained for the composite containing SBS, while greater elongation at break and impact strength values were recorded for the SEBS-containing system. In addition, a remarkable dispersion in the MAPP-containing composite and two times smaller average particle size were revealed by the SEM analysis for the SEBS particles compared to the SBS ones. The higher affinity of SEBS for PP compared to that for SBS and the different morphological characteristics of the systems containing SEBS and SBS may explain the different effects of these impact modifiers on the mechanical properties of the composites. The composites developed in this work were designed as substitutes for the fully synthetic polymeric materials or metal components used in the manufacturing of automotive parts.

Behavior of the Flexural Strength of Hemp/Polypropylene Composites: Evaluation of the Intrinsic Flexural Strength of Untreated Hemp Strands

The growing demand for plant fiber-reinforced composites offers new opportunities to compete against glass fiber (GF)-reinforced composites, but their performance must be assessed, revised, and improved as much as possible. This work reports on the production and the flexural strength of composites from polypropylene (PP) and hemp strands (20-50 wt.%), using maleic anhydride-grafted PP (MAPP) as a compatibilizer. A computational assessment of the reaction between cellulose and MAPP suggested the formation of only one ester bond per maleic anhydride unit as the most stable product. We determined the most favorable MAPP dosage to be 0.06 g per gram of fiber. The maximum enhancement in flexural strength that was attained with this proportion of MAPP was 148%, corresponding to the maximum fiber load. The modified rule of mixtures and the assumption of similar coupling factors for tensile and flexural strength allowed us to estimate the intrinsic flexural strength of hemp strands as 953 ± 116 MPa. While falling short of the values for sized GF (2415 MPa), the reinforcement efficiency parameter of the natural fibers (0.209) was found to be higher than that of GF (0.045).

The Mechanical Properties of Plant Fiber-Reinforced Geopolymers: A Review

Both geopolymer and plant fiber (PF) meet the requirements of sustainable development. Geopolymers have the advantages of simple preparation process, conservation and environmental protection, high early strength, wide source of raw materials, and low cost. They have broad application prospects and are considered as the most potential cementitious materials to replace cement. However, due to the ceramic-like shape and brittleness of geopolymers, their flexural strength and tensile strength are poor, and they are sensitive to microcracks. In order to solve the brittleness problem of geopolymers, the toughness of composites can be improved by adding fibers. Adding fibers to geopolymers can limit the growth of cracks and enhance the ductility, toughness and tensile strength of geopolymers. PF is a good natural polymer material, with the advantages of low density, high aspect ratio. It is not only cheap, easy to obtain, abundant sources, but also can be repeatedly processed and biodegradable. PF has high strength and low hardness, which can improve the toughness of composites. Nowadays, the research and engineering application of plant fiber-reinforced geopolymers (PFRGs) are more and more extensive. In this paper, the recent studies on mechanical properties of PFRGs were reviewed. The characteristics of plant fibers and the composition, structure and properties of geopolymers were reviewed. The compatibility of geopolymer material and plant fiber and the degradation of fiber in the substrate were analyzed. From the perspective of the effect of plant fibers on the compression, tensile and bending properties of geopolymer, the reinforcing mechanism of plant fibers on geopolymer was analyzed. Meanwhile, the effect of PF pretreatment on the mechanical properties of the PFRGs was analyzed. Through the comprehensive analysis of PFFRGs, the limitations and recommendations of PFFRG are put forward.

Mechanical Response and Failure Mechanisms of Natural Bamboo Fiber Reinforced Poly-Benzoxazine Composite Subjected to Split-Hopkinson Tensile Bar Loading

In this study, chopped natural bamboo fibers were successfully added in the benzoxazine matrix by the hot-pressing method to fabricate environmentally friendly bio-composite. The mechanical behaviors and failure mechanisms of neat benzoxazine matrix and its bamboo fiber composite under different tensile strain rates (quasi-static, 35/s and 110/s) were comparatively investigated using SHTB device (split-Hopkinson tensile bar), high-speed camera, DIC method (digital image correlation), and SEM observation (scanning electron microscopy). The results showed the composite exhibited 30.02% and 25.21% higher strength than that of neat benzoxazine under strain rates of 35/s and 110/s, respectively. However, under quasi-static tensile loading, the tensile strength of the composite was not higher than that of neat benzoxazine. The SEM and high-speed camera images showed the bamboo fibers displayed different reinforcing mechanisms under different strain rates. The chopped bamboo fibers could strengthen the composite effectively under dynamic tensile loadings. However, under quasi-static loading, the tensile strength of the composite was largely determined by the potential defects (such as small bubbles, pores, and fiber agglomerations) in the composite.

Recent Advances in the Development of Fire-Resistant Biocomposites—A Review

Biocomposites reinforced with natural fibers represent an eco-friendly and inexpensive alternative to conventional petroleum-based materials and have been increasingly utilized in a wide variety of industrial applications due to their numerous advantages, such as their good mechanical properties, low production costs, renewability, and biodegradability. However, these engineered composite materials have inherent downsides, such as their increased flammability when subjected to heat flux or flame initiators, which can limit their range of applications. As a result, certain attempts are still being made to reduce the flammability of biocomposites. The combustion of biobased composites can potentially create life-threatening conditions in buildings, resulting in substantial human and material losses. Additives known as flame-retardants (FRs) have been commonly used to improve the fire protection of wood and biocomposite materials, textiles, and other fields for the purpose of widening their application areas. At present, this practice is very common in the construction sector due to stringent fire safety regulations on residential and public buildings. The aim of this study was to present and discuss recent advances in the development of fire-resistant biocomposites. The flammability of wood and natural fibers as material resources to produce biocomposites was researched to build a holistic picture. Furthermore, the potential of lignin as an eco-friendly and low-cost FR additive to produce high-performance biocomposites with improved technological and fire properties was also discussed in detail. The development of sustainable FR systems, based on renewable raw materials, represents a viable and promising approach to manufacturing biocomposites with improved fire resistance, lower environmental footprint, and enhanced health and safety performance.