A Review of Sisal Fiber-Reinforced Geopolymers: Preparation, Microstructure, and Mechanical Properties.

The early strength of geopolymers (GPs) and their composites is higher, and the hardening speed is faster than that of ordinary cementitious materials. Due to their wide source of raw materials, low energy consumption in the production process, and lower emissions of pollutants, they are considered to have the most potential to replace ordinary Portland cement. However, similar to other inorganic materials, the GPs themselves have weak flexural and tensile strength and are sensitive to micro-cracks. Improving the toughness of GP materials can be achieved by adding an appropriate amount of fiber materials into the matrix. The use of discrete staple fibers shows great potential in improving the toughness of GPs. Sisal is a natural fiber that is reproducible and easy to obtain. Due to its good mechanical properties, low cost, and low carbon energy usage, sisal fiber (SF) is a GP composite reinforcement with potential development. In this paper, the research progress on the effect of SF on the properties of GP composites in recent decades is reviewed. It mainly includes the chemical composition and physical properties of SFs, the preparation technology of sisal-reinforced geopolymers (SFRGs), the microstructure analysis of the interface of SFs and the GP matrix, and the macroscopic mechanical properties of SFRGs. The properties of SFs make them have good bonding properties with the GP matrix. The addition of SFs can improve the flexural strength and tensile strength of GP composites, and SFRGs have good engineering application prospects.

Starch-fiber foaming biodegradable composites with polylactic acid hydrophobic surface.

Starch and plant fibers are abundant natural polymers that offer biodegradability, making them potential substitutes for plastics in certain applications, but are usually limited by its high hydrophilicity, and low mechanical performance. To address this issue, polylactic acid (PLA) is blended with cellulose and chitosan to create a waterproof film that can be applied to starch-fiber foaming biodegradable composites to enhance their water resistance properties. Here, plant fibers as a reinforcement is incorporated to the modified starch by foaming mold at 260 °C, and PLA based hydrophobic film is coated onto the surface to prepare the novel hydrophobic bio-composites. The developed bio-composite exhibits comprehensive water barrier properties, which is significantly better than that of traditional starch and cellulose based materials. Introducing PLA films decreases water vapor permeability from 766.83 g/m2·24h to 664.89 g/m2·24h, and reduce hysteresis angles from 15.57° to 8.59° within the first five minutes after exposure to moisture. The water absorption rate of PLA films also decreases significantly from 12.3 % to 7.9 %. Additionally, incorporating hydrophobic films not only enhances overall waterproof performance but also improves mechanical properties of the bio-composites. The fabricated bio-composite demonstrates improved tensile strength from 2.09 MPa to 3.53 MPa.

Interplay between Livestock Grazing and Aridity on the Ecological and Nutritional Value of Forage in Semi-arid Mediterranean Rangelands (NE Spain).

Rangeland-based livestock production constitutes a primary source of livelihood for many inhabitants of dryland regions. Their subsistence relies heavily on maintaining the productivity, biodiversity and services of these ecosystems. Harsh environmental conditions (e.g., drought) combined with land use intensification (e.g., overgrazing) make dryland ecosystems vulnerable and prone to degradation. However, the interplay between livestock grazing intensity and aridity conditions in driving the conservation and nutritional value of forage in arid and semi-arid rangelands is still not fully understood. In this study, we performed structural equation models (SEM) to assess the simultaneous direct and indirect effects of livestock grazing intensity and aridity level on community structure, diversity, biomass, forage production, forage C:N ratio and forage fiber composition in two semi-arid Mediterranean rangelands, NE Spain. Not surprisingly, we found that higher livestock grazing intensity led to lower community plant cover, especially when combined with higher aridity. However, both increasing grazing intensity and aridity were associated with higher forage production after one year of grazing exclusion. We did not find any adverse effect of livestock grazing on plant diversity, although plant species composition differed among grazing intensity levels. On the other hand, we found an aridity-driven trade-off in regard of the nutritional value of forage. Specifically, higher aridity was associated with a decrease in the least digestible fiber fraction (i.e., lignin) and an increase in forage C:N ratio. More interestingly, we found that livestock grazing modulated this trade-off by improving the overall forage nutritional value. Altogether, our results provide further insights into the management of semi-arid Mediterranean rangelands, pointing out that maintaining traditional rangeland-based livestock production may be a sustainable option as long as rangeland conservation (e.g., community plant cover) is not severely compromised.

The multi-kingdom microbiome of the goat gastrointestinal tract.

BACKGROUND: Goat is an important livestock worldwide, which plays an indispensable role in human life by providing meat, milk, fiber, and pelts. Despite recent significant advances in microbiome studies, a comprehensive survey on the goat microbiomes covering gastrointestinal tract (GIT) sites, developmental stages, feeding styles, and geographical factors is still unavailable. Here, we surveyed its multi-kingdom microbial communities using 497 samples from ten sites along the goat GIT. RESULTS: We reconstructed a goat multi-kingdom microbiome catalog (GMMC) including 4004 bacterial, 71 archaeal, and 7204 viral genomes and annotated over 4,817,256 non-redundant protein-coding genes. We revealed patterns of feeding-driven microbial community dynamics along the goat GIT sites which were likely associated with gastrointestinal food digestion and absorption capabilities and disease risks, and identified an abundance of large intestine-enriched genera involved in plant fiber digestion. We quantified the effects of various factors affecting the distribution and abundance of methane-producing microbes including the GIT site, age, feeding style, and geography, and identified 68 virulent viruses targeting the methane producers via a comprehensive virus-bacterium/archaea interaction network. CONCLUSIONS: Together, our GMMC catalog provides functional insights of the goat GIT microbiota through microbiome-host interactions and paves the way to microbial interventions for better goat and eco-environmental qualities. Video Abstract.

Recent Progress on Moisture Absorption Aging of Plant Fiber Reinforced Polymer Composites.

Plant fiber reinforced polymer matrix composites have attracted much attention in many industries due to their abundant resources, low cost, biodegradability, and lightweight properties. Compared with synthetic fibers, various plant fibers are easy to obtain and have different characteristics, making them a substitute for synthetic fiber composite materials. However, the aging phenomenon of composite materials has been a key issue that hinders development. In natural environments, moisture absorption performance leads to serious degradation of the mechanical properties of composite materials, which delays the use of composite materials in humid environments. Therefore, the effects of moisture absorption performance of plant fiber composite materials on their mechanical properties have been summarized in this article, as well as various treatment methods to reduce the water absorption of composite materials.

Mechanical Performances Analysis and Prediction of Short Plant Fiber-Reinforced PLA Composites.

Plant fiber-reinforced polylactic acid (PLA) exhibits excellent mechanical properties and environmental friendliness and, therefore, has a wide range of applications. This study investigated the mechanical properties of three short plant fiber-reinforced PLA composites (flax, jute, and ramie) using mechanical testing and material characterization techniques (SEM, FTIR, and DSC). Additionally, we propose a methodology for predicting the mechanical properties of high-content short plant fiber-reinforced composite materials. Results indicate that flax fibers provide the optimal reinforcement effect due to differences in fiber composition and microstructure. Surface pretreatment of the fibers using alkali and silane coupling agents increases the fiber-matrix interface contact area, improves interface performance, and effectively enhances the mechanical properties of the composite. The mechanical properties of the composites increase with increasing fiber content, reaching the highest value at 40%, which is 38.79% higher than pure PLA. However, further increases in content lead to fiber agglomeration and decreased composite properties. When the content is relatively low (10%), the mechanical properties are degraded because of internal defects in the material, which is 40.42% lower than pure PLA. Through Micro-CT technology, the fiber was reconstructed, and it was found that the fiber was distributed mainly along the direction of injection molding, and the twin-screw process changes the shape and length of the fiber. By introducing the fiber agglomeration factor function and correcting the Halpin-Tsai criterion, the mechanical properties of composite materials with different contents were successfully predicted. Considering the complex stress state of composite materials in actual service processes, a numerical simulation method was established based on transversely isotropic material using the finite element method combined with theoretical analysis. The mechanical properties of high-content short plant fiber-reinforced composite materials were successfully predicted, and the simulation results showed strong agreement with the experimental results.

Unveiling Sustainable Potential: A Life Cycle Assessment of Plant-Fiber Composite Microcellular Foam Molded Automotive Components.

The development and utilization of new plant-fiber composite materials and microcellular foam molding processes for the manufacturing of automotive components are effective approaches when achieving the lightweight, low-carbon, and sustainable development of automobiles. However, current research in this field has mainly focused on component performance development and functional exploration, with a limited assessment of environmental performance, which fails to meet the requirements of the current green and sustainable development agenda. In this study, based on a life cycle assessment, the resource, and environmental impacts of plant-fiber composite material automotive components and microcellular foam molding processes were investigated. Furthermore, a combined approach to digital twinning and life cycle evaluation was proposed to conduct resource and environmental assessments and analysis. The research results indicate that under current technological conditions, resource and environmental issues associated with plant-fiber composite material automotive components are significantly higher than those of traditional material components, mainly due to differences in their early-stage processes and the consumption of electrical energy and chemical raw materials. It is noteworthy that electricity consumption is the largest influencing factor that causes environmental issues throughout the life cycle, especially accounting for more than 42% of indicators such as ozone depletion, fossil resource consumption, and carbon dioxide emissions. Additionally, the microcellular foam molding process can effectively reduce the environmental impact of products by approximately 15% and exhibits better overall environmental performance compared to chemical foaming. In future development, optimizing the forming process of plant-fiber composite materials, increasing the proportion of clean energy use, and promoting the adoption of microcellular foam injection molding processes could be crucial for the green and sustainable development of automotive components.

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.

The current status and trends of DNA extraction.

DNA extraction, playing an irreplaceable role in molecular biology as it is an essential step prior to various downstream biological analyses. Thus, the accuracy and reliability of downstream research outcomes depend largely on upstream DNA extraction methodology. However, with the advancement of downstream DNA detection techniques, the development of corresponding DNA extraction methods is lagging behind. The most innovative DNA extraction techniques are silica- or magnetic-based. Recent studies have demonstrated that plant fiber-based adsorbents (PF-BAs) have stronger DNA capturing ability than classic materials. Moreover, magnetic ionic liquid (MIL)-based DNA extraction has gathered attention lately, and extrachromosomal circular DNA (eccDNA), cell-free DNA (cfDNA), and microbial community DNA are current research hotspots. These require specific extraction methods, along with constant improvements in the way they are used. This review discusses the significance as well as the direction of innovation of DNA extraction methods to try to provide valuable references including current status and trends for DNA extraction.

Elucidation of Non-Intentionally Added Substances from Plant Fiber/Plastic Composites by UPLC-QTOF/MS.

Plant fiber/plastic composites (PPCs) have been widely used in food contact materials (FCMs) for many benefits, such as their claimed better environmental footprint compared to conventional plastics. However, their safety is still not fully understood and must be comprehensively evaluated. Non-volatiles extracted from six PPCs with different plant fibers and polymer matrices were characterized by employing ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry in combination with various spectral libraries and manual elucidation, taking into account spectral similarity and characteristic product ions. A total of 115 compounds were tentatively identified, 50 of which were oligomers or their derivatives from the sample with polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) as the polymer matrix, and some of them were Cramer rules class III substances based on the threshold of toxicological concern (TTC). Seven reaction products between PLA and PBAT monomers, as well as four derivatives of melamine, were elucidated and well detailed for the first time. In addition, bisphenol S was detected in all samples even though its origin remains to be further explored. Isoprothiolane, as an insecticide and fungicide used to control a range of rice pests, was identified in the sample with rice husk as fillers, experimentally confirming the presence of agrochemicals in samples containing plant fibers.

Alkaline Degradation of Plant Fiber Reinforcements in Geopolymer: A Review.

Plant fibers (PFs), such as hemp, Coir, and straw, are abundant in resources, low in price, light weight, biodegradable, have good adhesion to the matrix, and have a broad prospect as reinforcements. However, the degradation of PFs in the alkaline matrix is one of the main factors that affects the durability of these composites. PFs have good compatibility with cement and the geopolymer matrix. They can induce gel growth of cement-based materials and have a good toughening effect. The water absorption of the hollow structure of the PF can accelerate the degradation of the fiber on the one hand and serve as the inner curing fiber for the continuous hydration of the base material on the other. PF is easily deteriorated in the alkaline matrix, which has a negative effect on composites. The classification and properties of PFs, the bonding mechanism of the interface between PF reinforcements and the matrix, the water absorption of PF, and its compatibility with the matrix were summarized. The degradation of PFs in the alkaline matrix and solution, drying and wetting cycle conditions, and high-temperature conditions were reviewed. Finally, some paths to improve the alkaline degradation of PF reinforcement in the alkaline matrix were proposed.

Piezoresistive Sensor Containing Lamellar MXene-Plant Fiber Sponge Obtained with Aqueous MXene Ink.

Sustainable biomass materials are promising for low-cost wearable piezoresistive pressure sensors, but these devices are still produced with time-consuming manufacturing processes and normally display low sensitivity and poor mechanical stability at low-pressure regimes. Here, an aqueous MXene ink obtained by simply ball-milling is developed as a conductive modifier to fabricate the multiresponsive bidirectional bending actuator and compressible MXene-plant fiber sponge (MX-PFS) for durable and wearable pressure sensors. The MX-PFS is fabricated by physically foaming MXene ink and plant fibers. It possesses a lamellar porous structure composed of one-dimensional (1D) MXene-coated plant fibers and two-dimensional (2D) MXene nanosheets, which significantly improves the compression capacity and elasticity. Consequently, the encapsulated piezoresistive sensor (PRS) exhibits large compressible strain (60%), excellent mechanical durability (10 000 cycles), low detection limit (20 Pa), high sensitivity (435.06 kPa-1), and rapid response time (40 ms) for practical wearable applications.

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.

Solar-assisted high-efficient cleanup of viscous crude oil spill using an ink-modified plant fiber sponge.

Rapid and efficient clean-up of viscous crude oil spills is still a global challenge due to its high viscous and poor flowability at room temperature. The hydrophobic/oleophilic absorbents with three-dimensional porous structure have been considered as a promising candidate to handle oil spills. However, they still have limited application in recovering the high viscous oil. Inspired by the viscosity of crude oil depended on the temperature, a solar-heated ink modified plant fiber sponge (PFS@GC) is fabricated via a simple and environmentally friendly physical foaming strategy combined with in-situ ink coating treatment. After wrapping by the polydimethylsiloxane (PDMS), the modified PFS@GC (PFS@GC@PDMS) exhibits excellent compressibility, high hydrophobic (141° in water contact angle), solar absorption (> 96.0%), and oil absorptive capacity (12.0-27.8 g/g). Benefiting from the favorable mechanical property and photothermal conversion capacity, PFS@GC@PDMS is demonstrated as a high-performance absorbent for crude oil clean-up and recovery. In addition, PFS@GC@PDMS can also be applied in a continuous absorption system for uninterrupted recovering of oil spills on the water surface. The proposed solar-heated absorbent design provides a new opportunity for exploring biomass in addressing large-scale oil spill disasters.

Durability of Cellulosic-Fiber-Reinforced Geopolymers: A Review.

Geopolymers have high early strength, fast hardening speed and wide sources of raw materials, and have good durability properties such as high temperature resistance and corrosion resistance. On the other hand, there are abundant sources of plant or cellulose fibers, and it has the advantages of having a low cost, a light weight, strong adhesion and biodegradability. In this context, the geopolymer sector is considering cellulose fibers as a sustainable reinforcement for developing composites. Cellulosic-fiber-reinforced geopolymer composites have broad development prospects. This paper presents a review of the literature research on the durability of cellulosic-fiber-reinforced geopolymer composites in recent years. In this paper, the typical properties of cellulose fibers are summarized, and the polymerization mechanism of geopolymers is briefly discussed. The factors influencing the durability of cellulosic-fiber-reinforced geopolymer composites were summarized and analyzed, including the degradation of fibers in a geopolymer matrix, the toughness of fiber against matrix cracking, the acid resistance, and resistance to chloride ion penetration, high temperature resistance, etc. Finally, the influence of nanomaterials on the properties of geopolymer composites and the chemical modification of fibers are analyzed, and the research on cellulosic-fiber-reinforced geopolymer composites is summarized.

Safety Risks of Plant Fiber/Plastic Composites (PPCs) Intended for Food Contact: A Review of Potential Hazards and Risk Management Measures.

Plant fiber/plastic composites (PPCs), with the benefits of low cost and easy processing, have been widely used in the production of various food contact products. They are generally considered to be economical and environmentally friendly because of their natural raw materials (plant fibers) and recommended to be one of the ideal alternatives to traditional petrochemical-based plastics. However, in addition to plastic resins and plant fibers, some indispensable additives are involved in the production process of PPCs, which may pose food safety risks. To date, excessive migration of hazardous substances (such as melamine) has been reported in some products made of PPCs, and the safety and applicability of PPCs as food contact materials need to be further studied. In this paper, the main raw materials of PPCs used for food contact are taken as the pointcut to analyze the possible hazards, sources of hazards, and existing risk management measures in various countries. The conclusion shows that PPCs used for food contact may have potential safety risks at present. However, systematic research on migration methods and safety assessment are still insufficient, and further studies are needed regarding the main safety risks and migration patterns.

Humans have intestinal bacteria that degrade the plant cell walls in herbivores.

The cell walls of plants are mainly made of cellulose and contain a large number of calories. However, the main component, cellulose, is an indigestible plant fiber that is thought to be difficult for humans to use as energy. Herbivores acquire energy through the degradation of cell wall-derived dietary fiber by microorganisms in the digestive tract. Herbivores, especially horses, have a highly developed cecum and large intestine, and plants are fermented for their efficient use with the help of microorganisms. Humans also have an intestinal tract with a wide lumen on the proximal side of the large intestine, in which fermentation occurs. The digestive process of horses is similar to that of humans, and many of the intestinal bacteria found in horses that degrade plants are also found in humans. Therefore, it is thought that humans also obtain a certain amount of energy from cell wall-derived dietary fiber. However, the intake of dietary fiber by modern humans is low; thus, the amount of calories derived from indigestible plant fiber is considered to be very low. Cellulose in the plant cell wall is often accompanied by hemicellulose, pectin, lignin, suberin, and other materials. These materials are hard to degrade, and cellulose is therefore difficult for animals to utilize. If the cell wall can be degraded to some extent by cooking, it is thought that humans can obtain calories from cell wall-derived dietary fiber. If humans can use the calories from the cell wall for their diet, it may compensate for human food shortages.

Low-Velocity Impact Analysis of Pineapple Leaf Fiber (PALF) Hybrid Composites.

The low-velocity impact behaviour of pineapple leaf fiber, PALF reinforce epoxy composite (P), PALF hybrid (GPG), and four-layer woven glass fiber (GGGG) composite was investigated. As for post-impact analysis, the damage evaluation was assessed through photographic images and X-ray computed tomography, using CT scan techniques. The key findings from this study are that a positive hybrid effect of PALF as a reinforcement was seen where the GPG shows the delayed time taken for damage initiation and propagation through the whole sample compared to GGGG. This clearly shows that the addition of fibers does have comparable composite properties with a fully synthetic composite. Through the visual inspection captured by photographic image, the presence of woven fiber glass mat in GPG presents a different damage mode compared to P. Moreover, CT scan results show extended internal damage at the cross-section of all impacted composite.

Importance of Interfacial Adhesion Condition on Characterization of Plant-Fiber-Reinforced Polymer Composites: A Review.

Plant fibers have become a highly sought-after material in the recent days as a result of raising environmental awareness and the realization of harmful effects imposed by synthetic fibers. Natural plant fibers have been widely used as fillers in fabricating plant-fibers-reinforced polymer composites. However, owing to the completely opposite nature of the plant fibers and polymer matrix, treatment is often required to enhance the compatibility between these two materials. Interfacial adhesion mechanisms are among the most influential yet seldom discussed factors that affect the physical, mechanical, and thermal properties of the plant-fibers-reinforced polymer composites. Therefore, this review paper expounds the importance of interfacial adhesion condition on the properties of plant-fiber-reinforced polymer composites. The advantages and disadvantages of natural plant fibers are discussed. Four important interface mechanism, namely interdiffusion, electrostatic adhesion, chemical adhesion, and mechanical interlocking are highlighted. In addition, quantifying and analysis techniques of interfacial adhesion condition is demonstrated. Lastly, the importance of interfacial adhesion condition on the performances of the plant fiber polymer composites performances is discussed. It can be seen that the physical and thermal properties as well as flexural strength of the composites are highly dependent on the interfacial adhesion condition.

Endoglucanase activity of cellulolytic bacteria from lake sediments and its application in hydrophyte degradation.

Hydrophytes are plants that grow in or on water. Their overgrowth adversely affects the ecosystem because of crowding out other aquatic organisms and polluting the environment with plant residue. In principle, cellulolytic bacteria can be used to degrade hydrophyte biomass. We here isolated and characterized four cellulolytic bacterial strains from Lake Donghu sediments (Wuhan, China) that are rich in organic matter and plant residues. The isolates (WDHS-01 to 04) represent Bacillus, Micromonospora and Streptomyces genera. The bacteria exhibited pronounced endoglucanase activities (from 0.022 to 0.064 U mL-1). They did not extensively degrade the emerged plant Canna indica L. However, in an Hydrilla verticillata (submerged plant) degradation medium, strain WDHS-02 exhibited a high degradation rate (54.91%), endoglucanase activity of 0.35 U mL-1 and the conversion rate of cellulose to reducing sugars of 7.15%. Correlation analysis revealed that bacterial endoglucanase activity was significantly correlated with the degradation rate, and acid detergent lignin, ash and cellulose content of the residual H. verticillata powder. In conclusion, the identified bacteria efficiently decomposed submerged plants without the need for acid-base pretreatment. They expand the set of known cellulolytic bacteria and can be used for natural degradation of submerged plants.