Natural Fiber Biocomposites Research Articles

Flame retardant characteristics of natural fibre reinforced polymer composites: A thematic review

AbstractGlobally, with the advancement of industrialization and globalization, the automotive sector has drastically increased for transportation and commercial purposes. Hence, to maximize efficiency and minimize the weight of automobiles, the automotive and aerospace industries have welcomed synthetic fibre‐reinforced composites, vastly replacing conventional metals. Despite the superior performance, the usage of synthetic fibre composites has led to the massive dumping of automotive waste in landfills, making the land unfit for future purposes. Therefore, natural fibre‐reinforced composites (NFRCs) quickly replace synthetic fibres with their unique features, such as being lightweight, biodegradable, and non‐toxic, en routing a new path towards a sustainable environment. Though NFRCs are finding new applications in various industries, researchers are trying to enhance their thermal, electrical, and mechanical properties to make them synergic composites. However, with the presence of cellulose, lignin, and wax, natural fibres become highly responsive toward flammability, limiting their use in various emerging applications. As the subject of the flammability of NFRCs has a limited amount of literature, the current review article aims to address the current flammability studies and strategies adopted to improve the flame‐retardant characteristics of NFRCs exclusively. Also, this review covers the factors and influence of different types of flame‐retardant fillers adopted to improve the flame retreatant characteristic of NFRCs and their mechanism. Additionally, this review article summarises various official and laboratory flame‐testing techniques such as radial panel test (RPT), cone calorimetry, and limited oxygen index (LOI) adopted to characterize the flammable properties of NFRCs.Highlights Natural fiber biocomposites are becoming a potential candidate for structural and interior applications in the automotive and aircraft industries. Flammability becomes a major alarm as it concerns with the safety of passengers. The flammability behavior of natural fiber composites is extensively discussed. Mechanisms, factors, and selection of flame‐retardant materials are reviewed to improve the flame‐retardant characteristics. The influence of surface treatments, fiber content, and flame‐retardant nanofillers are also elaborately discussed. Advanced flame testing techniques were conversed with pictorial representation.

Natural fiber biocomposites via 4D printing technologies: a review of possibilities for agricultural bio-mulching and related sustainable applications

Natural fiber biocomposites via 4D printing technologies: a review of possibilities for agricultural bio-mulching and related sustainable applications

Fabrication and characterization of polylactic acid/natural fiber extruded composites

AbstractIn this work, the fabricated polylactic acid (PLA) and hybrid natural fiber (NF) biocomposites via a melt extrusion method were investigated. NFs from locally grown plants were utilized as fillers. Polyethene glycol (PEG) was used as the plasticizer to improve the processability of the PLA. The effect of PLA/NF biocomposite processing was assessed by mechanical characterization (tensile, modulus, strain at break, and impact tests), and thermal properties (thermogravimetric analysis and differential scanning calorimetry [DSC] analysis). The dynamic mechanical analysis (DMA), and thermo‐mechanical analysis (TMA) of the samples were also analyzed. The mechanical properties of PLA/NF biocomposites improved as compared with that of PLA. The DMA findings show that the storage modulus and loss modulus exhibited a slight reduction for PLA/NF biocomposites compared with the PLA sample. In opposite, the glass transition temperature (Tg) from DSC thermogram results showed no obvious changes in values compared with the PLA sample. Furthermore, the findings of TMA showed a significant decrease in coefficient of thermal expansion values of PLA/NF biocomposites compared with those of PLA samples. The overall findings from this work indicated that PLA/NF biocomposites have the potential to make novel biocomposites and suitable for further application especially in biomedical applications due to its good stiffness, tensile strength, and dimensional stability.

Statistical predicting and optimization of the tensile properties of natural fiber bio-composites

Statistical predicting and optimization of the tensile properties of natural fiber bio-composites

Colombian Sustainability Perspective on Fused Deposition Modeling Technology: Opportunity to Develop Recycled and Biobased 3D Printing Filaments.

In the context of the preservation of natural resources, researchers show a growing interest in developing eco-friendly materials based on recycled polymers and natural fiber biocomposites to minimize plastic and agroindustrial waste pollution. The development of new materials must be integrated within the circular economy concepts to guarantee sustainable production. In parallel, fused deposition modeling, an additive manufacturing technology, provides the opportunity to use these new materials in an efficient and sustainable manner. This review presents the context of plastics and agro-industrial fiber pollution, followed by the opportunity to give them added value by applying circular economy concepts and implementing these residues to develop new materials for the manufacture of fused deposition modeling 3D printing technique feedstock. Colombian perspective is highlighted since 3D printing technology is growing there, and Colombian biodiversity represents a high reservoir of materials. Also, recycling in Colombia promotes compliance with the 2030 Agenda and the Sustainable Development Goals.

Structure and mechanical behavior of lignosulfonate-treated piassava (Attalea funifera) fibers

The use of natural lignocellulosic fiber (NLF) biocomposites for the construction industry has been growing over the years, due to technical and environmental advantages. However, fiber-matrix incompatibility remains a major challenge. Various surface treatments have been investigated to improve fiber-matrix bonding, including sodium lignosulfonate (SLS), a potentially effective and environmentally friendly chemical. In this study, SLS treatment protocols were applied to piassava fibers to evaluate their influence on the fibers. Thermogravimetric Analysis (TG/DTG), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM/EDS), Fourier-transform Infrared Spectroscopy (FTIR), moisture absorption measurements and tensile tests were performed to characterize the modifications. Results demonstrated, for the first time, the efficiency of SLS to remove extractives from the piassava surface. In general, partial degradation of the cellulosic structure was observed, noticeable by the slight drop in crystallinity index (from 42.80 to 39.82%), and an increase in the TG residual mass (from 21.35 to 31.90%), along with changes in DTG curves. However, a particular SLS treatment using ultrasonic bath was able to fully clean the surface preserving the cellulosic structure, and increasing the strength of fibers (from 386 ± 140 MPa to 524 ± 126 MPa).

Recent Development in the Processing, Properties, and Applications of Epoxy-Based Natural Fiber Polymer Biocomposites

Growing environmental concerns have increased the scientific interest in the utilization of natural fibers for the development of epoxy biocomposite materials. The incorporation of one or more fibers in the production of hybrid epoxy polymer composites has been a subject of discussion. It is interesting to acknowledge that natural/synthetic fiber hybridized epoxy composites have superior properties over natural/natural fiber hybridized epoxy composites. Significant efforts have been devoted to the improvement of natural fiber surface modifications to promote bonding with the epoxy matrix. However, to achieve sufficient surface modification without destroying the natural fibers, optimization of treatment parameters such as the concentration of the treatment solution and treatment time is highly necessary. Synthetic and treated natural fiber hybridization in an epoxy matrix is expected to produce biocomposites with appreciable biodegradability and superior mechanical properties by manipulating the fiber/matrix interfacial bonding. This paper presents a review of studies on the processing of epoxy natural fiber composites, mechanical properties, physical properties such as density and water absorption, thermal properties, biodegradability study, nondestructive examination, morphological characterizations, and applications of epoxy-based natural fiber biocomposites. Other aspects, including a review of variables that enhance the mechanical and functional performance of epoxy/natural fibers composites while also increasing the biodegradability of the composite material for environmental sustainability, were presented. The future research focus was elucidated. It is hoped that this review will stimulate and refocus research efforts toward advancing the manufacture of epoxy/natural fiber composites to meet the growing demand for biocomposite materials in the global world.

A Comprehensive Review on Construction Applications and Life Cycle Sustainability of Natural Fiber Biocomposites

The construction industry is continuously searching for sustainable materials to combat the rapid depletion of global resources and ongoing ecological crises. Biocomposites have recently received global attention in various industries due to their renewability, low cost, and biodegradability. Biocomposites’ potential as a sustainable substitute in construction can be understood by identifying their diverse applications. Moreover, examining their life cycle environmental and economic impacts is important. Therefore, this study is a novel attempt to encompass biocomposites’ construction applications and their environmental life cycle performance. Statistical analysis is done related to the temporal distribution of papers, publishers, literature type and regions of studies. First, this paper reviews the latest research on the applications of natural fiber biocomposites in construction with their key findings. The applications include fiber reinforcements in concrete, external strengthening elements, internally filled hollow tubes, wood replacement boards, insulation, and non-structural members. The second part covers the life cycle assessment (LCA) and cost studies on biocomposites. The life cycle studies are currently rare and require more case-specific assessments; however, they highlight the benefits of biocomposites in cost savings and environmental protection. Finally, this study provides key suggestions for increasing the applicability of biocomposites as sustainable construction materials.

An overview: characterization of natural fiber reinforced hybrid composites

Purpose The purpose of this study is to understand the behavior of hybrid bio-composites under varied applications. Design/methodology/approach Fabrication methods and material characterization of various hybrid bio-composites are analyzed by studying the tensile, impact, flexural and hardness of the same. The natural fiber is a manufactured group of assembly of big or short bundles of fiber to produce one or more layers of flat sheets. The natural fiber-reinforced composite materials offer a wide range of properties that are suitable for many engineering-related fields like aerospace, automotive areas. The main characteristics of natural fiber composites are durability, low cost, low weight, high specific strength and equally good mechanical properties. Findings The tensile properties like tensile strength and tensile modulus of flax/hemp/sisal/Coir/Palmyra fiber-reinforced composites are majorly dependent on the chemical treatment and catalyst usage with fiber. The flexural properties of flax/hemp/sisal/coir/Palmyra are greatly dependent on fiber orientation and fiber length. Impact properties of flax/hemp/sisal/coir/Palmyra are depended on the fiber content, composition and orientation of various fibers. Originality/value This study is a review of various research work done on the natural fiber bio-composites exhibiting the factors to be considered for specific load conditions.

A Review on Natural Fiber Bio-Composites, Surface Modifications and Applications.

Increased environmental concerns and global warming have diverted focus from eco-friendly bio-composites. Naturals fibers are abundant and have low harvesting costs with adequate mechanical properties. Hazards of synthetic fibers, recycling issues, and toxic byproducts are the main driving factors in the research and development of bio-composites. Bio-composites are degradable, renewable, non-abrasive, and non-toxic, with comparable properties to those of synthetic fiber composites and used in many applications in various fields. A detailed analysis is carried out in this review paper to discuss developments in bio-composites. The review covers structure, morphology, and modifications of fiber, mechanical properties, degradable matrix materials, applications, and limitations of bio-composites. Some of the key sectors employing bio-composites are the construction, automobile, and packaging industries. Furthermore, bio-composites are used in the field of medicine and cosmetics.

Fabrication and Characterization of Microcellular Polyurethane Sisal Biocomposites.

In this study, microcellular polyurethane (PU)-natural fiber (NF) biocomposites were fabricated. Polyurethanes based on castor oil and PMDI were synthesized with varying volume ratios of sisal fiber. The effect of natural fiber treatment using water and alkaline solution (1.5% NaOH) and load effect were investigated. Biocomposites were mechanically and physically investigated using tensile, viscoelasticity, and water absorption tests. The interfacial adhesion between PU and sisal fiber was studied using SEM. Short NF loads (3%) showed a significant improvement in the mechanical properties of the PU-sisal composite such as modulus of elasticity, yield and tensile strength up to 133%, 14.35 % and 36.7% respectively. Viscoelastic measurements showed that the composites exhibit an elastic trend as the real compliance (J’) values were higher than those of the imaginary compliance (J’’). Increasing NF loads resulted in a decrease of J’. Applying variable temperatures (120–80 °C) caused an increase in the stiffness at different frequencies.

Plasticized starch-based biocomposites containing modified rice straw fillers with thermoplastic, thermoset-like and thermoset chemical structures

In this work, rice straw (RS) as an abundant biomass was applied to prepare some renewable thermoplastic materials by using soda-pulping and benzylation processes. The obtained RS products including untreated RS, RS pulp, benzylated RS pulp and pulping liquor as well as benzylated RS were incorporated into the thermoplastic starch through a twin-screw extrusion process to obtain all green composites. The successful thermoplasticization reaction of RS products was confirmed by spectroscopy results and morphological observations. The interfacial adhesion between the plasticized starch matrix and the RS products is enhanced by the chemical modifications, which confirmed by investigating through the morphological observations and linear rheological responses. The partial phase miscibility of the plasticizer/starch mixtures is improved by adding the benzylated RS and RS pulp. The RS pulp having cellulosic microfibers enhances the Young modulus and tensile strength of the plasticized starch even more than untreated RS. However, their thermoset and thermoset-like structure leads to the brittle failure mode of the starch biocomposites, similar to the common natural fiber biocomposites. The thermoplasticization reaction changes the failure mode and significantly improves the toughness of the plasticized starch/RS product biocomposites owing to better phase miscibility.

Interfacial reinforcement mechanism in poly(lactic acid)/natural fiber biocomposites featuring ZnO nanowires at the interface

Poly(lactic acid) (PLA)/natural fiber (NF) biocomposite is available from renewable resources and can degrade totally in the environment, but suffers from poor interfacial adhesion. Here, we adopted two-step hydrothermal method to functionalize zinc oxide (ZnO) nanowires on the NF surface driven by strong intramolecular interaction. The perfect integration of the root-like NF and PLA matrix via the laterally-grown ZnO nanowires enabled the corresponding composite to present excellent interfacial adhesion. This can be exemplified by the substantial increases of 157% and 403% in interfacial shear strength and the debonding energy compared to PLA/pristine NF composite. Finally, a comprehensive understanding on the interfacial reinforcement caused by the laterally-grown ZnO nanowires was elucidated based on finite element method and the fracture morphology after the single fiber pull-out test. This study can provide an interfacial manipulation strategy on topological architecture to improve the interfacial properties of the environmentally-friendly PLA/NF biocomposite, which is instructive to achieve the large-scale application.

Thermal analysis, statistical predicting, and optimization of the flexural properties of natural fiber biocomposites using Box–Behnken experimental design

ABSTRACTThe object of this study is to investigate the flexural properties of biocomposites based on polypropylene/kenaf fiber/polypropylene-grafted maleic anhydride (PP/kenaf/PP-g-MA) using the response surface methodology. A three-factor, three-level Box–Behnken design, which is the subset of the response surface methodology, has been applied to present mathematical models as a function of kenaf fiber load, fiber length, and PP-g-MA compatibilizer content for the prediction of flexural strength and modulus behavior of the natural fiber biocomposite. Three levels were chosen for the considered parameters as follows: kenaf fiber (10–30 wt%), fiber length (2–10 mm), and PP-g-MA (1–5 wt%). Optimum compositions for better flexural properties were obtained from contour plots and response surface methodology. The results obtained using the design expert software showed the optimal flexural strength and modulus to be 53.66 and 3442 MPa, respectively. The obtained values and normal probability plots indicated a good agreement between the experimental results and those predicted by the model. Finally, the morphology and thermal stability of the samples were evaluated by scanning electron microscopy and thermogravimetric analysis.

An experimental investigation and optimization on the impact strength of kenaf fiber biocomposite: application of response surface methodology

A big scientific challenge of biocomposites is in improving impact strength. Thus, the key aspect of the present study is in investigating an in-depth statistical approach on influence of processing parameters on the impact strength of the biocomposite. Natural fiber biocomposites, consisting of polypropylene (PP) and kenaf as natural fiber, were produced using melt blending. The simultaneous effects of different parameters including kenaf fiber loading, fiber length and polypropylene-grafted maleic anhydride (PP-g-MA) compatibilizer content on the impact strength have been evaluated. Response surface methodology (RSM) based on Box–Behnken design (BBD) was used to design the experiments. The optimum impact strength of 30.76 j/m was obtained with kenaf fiber loading of 26.77 wt%, fiber length of 6.09 mm and PP-g-MA content of 5 wt%. The biocomposites prepared with optimum levels of fabrication process parameters that were obtained using the response surface graph and models, had a 19% increase in impact strength than pure PP. Among the selected processing parameters, fiber loading has a most significant effect on the impact strength of the biocomposites. The thermal behavior of the kenaf fiber was evaluated from TGA/DTG thermograms. The fiber-matrix morphology in the treated biocomposites with PP-g-MA was confirmed by SEM analysis of the fractured specimens. FTIR spectra of the biocomposite with and without PP-g-MA were also studied to ascertain the existence of type of interfacial bonds. Finally, the crystallinity of PP and the biocomposites were also studied through DSC measurements.

Modeling and optimization of tensile strength and modulus of polypropylene/kenaf fiber biocomposites using Box–Behnken response surface method

The aim of this work includes modeling and optimization of the tensile properties of natural fiber biocomposites using the concept of experimental design. A three‐factor, three‐level Box–Behnken design, which is subset of the response surface methodology (RSM), has been applied to present mathematical models. The effect of three independent variables; kenaf fiber load, fiber length and polypropylene‐grafted maleic anhydride (PP‐g‐MA) compatibilizer content have been investigated on the tensile strength and modulus of polypropylene/kenaf fiber/PP‐g‐MA biocomposite. These models can be used as an interesting method for analytically evaluating both the tensile strength values and their corresponding tensile modulus as function of independent variables. The optimization results, obtained using the optimization part of Design‐Expert Software, showed that the most optimal tensile strength and tensile modulus were to be 32.70 MPa and 2,182.33 MPa, respectively; and achieved at 28.95 wt% of the kenaf fiber, fiber length of 6.22 mm and PP‐g‐MA content of 5 wt%. The obtained values and normal probability plots indicated a good agreement between the experimental results and those predicted by the model (above 0.95 for all the responses). Moreover, the tensile modulus of the biocomposite was analyzed by means of micromechanical models. The performance of the Halpin–Tsai and Cox–Krenchel models in predicting the tensile modulus of biocomposites was compared with available experimental results. In addition, the fracture surface morphologies and wettability of the samples were investigated by scanning electron microscopy (SEM) and contact angle measurement, respectively. It was found that the fiber load and PP‐g‐MA compatibilizer content play a significant role in the tensile properties and morphology of the biocomposites, as proven by SEM and contact angle measurement. POLYM. COMPOS., 39:E463–E479, 2018. © 2017 Society of Plastics Engineers

Biocomposites reinforced with natural fibers:thermal, morphological and mechanical characterization

ABSTRACT This study evaluates the thermal, morphological and mechanical behavior of polypropylene (PP) composite with different natural fibers. The fibers used were wood, sugarcane, bamboo, babassu, coconut and kenaf with and without coupling agent. The thermal, morphological and mechanical properties were evaluated, and a composite PP+GFPP (glass fiber) was used as reference. The interaction at the interface fiber-polymer matrix was studied by scanning electron microscopy (SEM) at the fractured surface of the composites, as expected the presence of maleic anhydride (MA) as coupling agent increasedthe interaction at the interface. The influence of natural fiber in the degree of crystallinity of the composites was evaluated by DSC analysis. The samples of PP+GFPP and PP+(PP-MA)+WF (wood flour) showed better temperature stability. PP+GF also presented superior flexural modulus. The thermal dynamic mechanical behavior was evaluated by DMA, a decrease in storage modulus with increasing temperature was observed, the PP+GF and the composite containing maleic anhydride and sugarcane fiber showed higher modulus. The natural fiber biocomposites studied, consistently presented lower flexural modulus and tensile strength than the reference composite, with and without the use of coupling agent. As expected the use of natural fibers lowered the density compared to the reference material.

Evaluating mold growth in tannin-resin and flax fiber biocomposites

Flax fiber is an industrially available, renewable product with attractive technical properties for the composite industry such as density, mechanical strength and sound/heat insulation. Applications are developing quickly for biocomposites based on these fibers. However, unlike plastics, there is no standard used to assess its degree of contamination by microorganisms. Thus, the aims of this work were to detect and quantify molds in samples of nonwoven fibrous materials from industry and high resin content natural matrix-natural fiber biocomposites. In a first attempt, we tried to evaluate the fungal development on the nonwoven materials as defined in the ISO 846 standard. Despite the materials having been inoculated with molds, no fungal mycelium could be detected by this way. To validate this observation, we developed a qualitative approach based on the specific aniline blue method to stain the mycelium present in the material. This allowed us to detect the mold occurrence in the material and to evaluate the colonization extent on the nonwoven fibrous materials incubated under different conditions. The biocide efficiency of a boric acid pretreatment of flax fibers used in the manufacturing process of nonwoven fibrous materials and high resin content natural matrix-natural fiber biocomposites was determined by grading the mold development using the microscope-based method that we developed. The results showed clearly that in optimal mold growth conditions, (Aw>0.6, 26°C) the colonization of the material was hampered by the boric acid pretreatment of the flax fibers. To get semi-quantitative data of the colonization extent, we used a molecular method. DNA was extracted from the different materials and the ribosomal region of the fungal DNA was amplified by PCR allowing the detection and the quantification of fungal colonization in the biosourced material. Results confirmed the microscopy-based method. Work is currently in progress to determine risk classes of mold colonization in wood-derived and fibrous-based composite materials.

Toward Stronger Transcrystalline Layers in Poly(l-lactic acid)/Natural Fiber Biocomposites with the Aid of an Accelerator of Chain Mobility

Formation of transcrystalline layer probably enhances the interfacial adhesion of poly(L-lactic acid) (PLLA)/natural fiber biocomposites as confirmed by this work. We found that a crystallization accelerator, poly(ethylene glycol) (PEG), improved chain mobility of PLLA and thus enhanced the growth kinetics of ramie fiber-induced transcrystallinity (TC). The direct observation of polarized optical microscopy during isothermal crystallization revealed that large-sized TC with rapid growth was produced after adding PEG. It could be exemplified by the case at 125 °C that the growth rate of TC developed in PLLA10 (containing 10 wt % PEG) achieved 6.1 μm/min, which was nearly triple that of pure PLLA (2.1 μm/min). And interestingly enough, spherulitic nucleation proceeding was largely restricted because it was difficult to fulfill the critical size for stable nuclei due to the increased chain mobility. Meanwhile, combining the effective nucleation activity of ramie fibers and acceleration virtue of PEG offered the chance to form prevailing TC texture, instead of rich spherulites dominated in pure PLLA. The local structure (including lamellar structure and molecular orientation) of transcrystalline layers was further determined, which indicated that TC presented α crystal form and random lamellar packing derived from the moderate nucleating ability. To our surprise, the single fiber reinforced composite samples containing prevailing TC textures achieved remarkably higher strength compared to that of pure PLLA samples with poorly developed transcrystalline layers, as demonstrated by the single-fiber pull-out test.

Hierarchical cellular designs for load-bearing biocomposite beams and plates

Scrutiny into the composition of natural, or biological materials convincingly reveals that high material and structural efficiency can be attained, even with moderate-quality constituents, by hierarchical topologies, i.e., successively organized material levels or layers. The present study demonstrates that biologically inspired hierarchical designs can help improve the moderate properties of natural fiber polymer composites or biocomposites and allow them to compete with conventional materials for load-bearing applications. An overview of the mechanics concepts that allow hierarchical designs to achieve higher performance is presented, followed by observation and results from flexural tests on periodic and hierarchical cellular beams and plates made from industrial hemp fibers and unsaturated polyester resin biocomposites. The experimental data is shown to agree well with performance indices predicted by mechanics models. A procedure for the multi-scale integrated material/structural analysis of hierarchical cellular biocomposite components is presented and its advantages and limitations are discussed.