Showing papers on "Natural fiber published in 2011"
TL;DR: In this paper, a review on the tensile properties of natural fiber reinforced polymer composites is presented, where several chemical modifications are employed to improve the interfacial matrix-fiber bonding resulting in the enhancement of tensile strength of the composites.
Abstract: This paper is a review on the tensile properties of natural fiber reinforced polymer composites. Natural fibers have recently become attractive to researchers, engineers and scientists as an alternative reinforcement for fiber reinforced polymer (FRP) composites. Due to their low cost, fairly good mechanical properties, high specific strength, non-abrasive, eco-friendly and bio-degradability characteristics, they are exploited as a replacement for the conventional fiber, such as glass, aramid and carbon. The tensile properties of natural fiber reinforce polymers (both thermoplastics and thermosets) are mainly influenced by the interfacial adhesion between the matrix and the fibers. Several chemical modifications are employed to improve the interfacial matrix–fiber bonding resulting in the enhancement of tensile properties of the composites. In general, the tensile strengths of the natural fiber reinforced polymer composites increase with fiber content, up to a maximum or optimum value, the value will then drop. However, the Young’s modulus of the natural fiber reinforced polymer composites increase with increasing fiber loading. Khoathane et al. [1] found that the tensile strength and Young’s modulus of composites reinforced with bleached hemp fibers increased incredibly with increasing fiber loading. Mathematical modelling was also mentioned. It was discovered that the rule of mixture (ROM) predicted and experimental tensile strength of different natural fibers reinforced HDPE composites were very close to each other. Halpin–Tsai equation was found to be the most effective equation in predicting the Young’s modulus of composites containing different types of natural fibers.
1,757 citations
TL;DR: In this paper, a chemical-purified cellulose fibers were then mechanically separated into nanofibers using high-intensity ultrasonication, and the diameter distributions of the resulting nanofiber were dependent on the output power of the ultrasonic treatment.
796 citations
TL;DR: In this article, the effect of alkali treatment on the surface morphology and mechanical properties of coir fibers, interfacial shear strength (IFSS) and structural properties of poly(butylene succinate) (PBS) composites was studied.
Abstract: The poly(butylene succinate) (PBS) biodegradable composites reinforced with coir fibers were developed. The effect of alkali treatment on the surface morphology and mechanical properties of coir fibers, interfacial shear strength (IFSS) and mechanical properties of coir fiber/PBS composites was studied. The effect of fiber mass content varying from 10% to 30% on the mechanical properties of coir fiber/PBS composites was also investigated. The coir fibers which are soaked in 5% sodium hydroxide solution at room temperature (RT) for 72 h showed the highest IFSS with 55.6% higher than untreated coir fibers. The mechanical properties of alkali-treated coir fiber/PBS composites are significantly higher than those of untreated fibers. The best mechanical properties of alkali-treated coir fiber/PBS composite were achieved at fiber mass content of 25% in this study, which showed an increase of tensile strength by 54.5%, tensile modulus by 141.9%, flexural strength by 45.7% and flexural modulus by 97.4% compared to those of pure PBS resin. The fiber surface morphologies and fractured surface of the composites exhibited an improvement of interfacial fiber–matrix adhesion in the composites reinforced with alkali-treated coir fibers.
364 citations
TL;DR: In this article, the effect of chemical treatments of fibers by alkalization on the flexural properties of polyester matrix composite reinforced with natural fibers was studied to determine the optimum conditions of alkaline treatment.
256 citations
TL;DR: In this article, commercial cellulase enzymes were used to fractionate the less recalcitrant amorphous cellulose from a bleached Kraft eucalyptus pulp, resulting in a highly crystalline and recalcrant cellulose (RC), which is difficult to hydrolyze to sugars but very suitable for producing biobased nanomaterials through mechanical homogenization.
219 citations
TL;DR: In this paper, physical, mechanical, and flammability properties of polypropylene (PP) composite panels were evaluated and the results suggest that an optimal composite panel formulation for automotive interior applications is a mixture of 60 wt % coir fiber, 37 Wt % PP powder, and 3 WT % maleic anhydride grafted PP powder.
Abstract: In this study, physical, mechanical, and flammability properties of coconut fiber reinforced polypropylene (PP) composite panels were evaluated. Four levels of the coir fiber content (40, 50, 60, and 70 % based on the composition by weight) were mixed with the PP powder and a coupling agent, 3 wt % maleic anhydride grafted PP (MAPP) powder. The water resistance and the internal bond strength of the composites were negatively influenced by increasing coir fiber content. However, the flexural strength, the tensile strength, and the hardness of the composites improved with increasing the coir fiber content up to 60 wt %. The flame retardancy of the composites improved with increasing coir fiber content. The results suggest that an optimal composite panel formulation for automotive interior applications is a mixture of 60 wt % coir fiber, 37 wt % PP powder, and 3 wt % MAPP.
211 citations
TL;DR: In this article, a novel mechanical extraction process was developed to obtain long bamboo fibers to be used as reinforcement in structural composites, and a single-fiber tensile test at four different span lengths for four span lengths was performed.
Abstract: A novel mechanical extraction process was developed to obtain long bamboo fibers to be used as reinforcement in structural composites. A single-fiber tensile test at four different span lengths for...
207 citations
TL;DR: In this paper, the sisal fibers were modified by alkali solutions of NaOH (5% and 10%) and bleached with sodium hyplochlorite NaClO/H2O (1:1) at 60-75°C.
Abstract: The sisal (Agave sisalana) is a cellulosic fiber produced in Brazil since 1903 and until now has been one of the most traded due to its characteristics such as the low cost, low density, specific resistance, biological degradability, CO2 neutrality, renewability, good mechanical properties, non-toxicity and furthermore can be easily modified by a chemical agent improving their mechanical and thermal properties. In this work, the sisal fibers were modified by alkali solutions of NaOH (5% and 10%) and bleached with sodium hyplochlorite NaClO/H2O (1:1) at 60–75 °C. It was used as reinforcing agent in the preparation of phenolic matrix composites derived from cashew nut shell liquid (CNSL). The chemical treatment improved the thermal stability of the weight loss process for sisal treated with NaOH 5% in about 12 °C and for sisal treated with NaOH 10% in about 18 °C when compared to sisal fiber in its raw state. It was also observed a variation of 15 °C when comparing the composite reinforced by raw sisal with composite reinforced with sisal treated NaOH 10%.
179 citations
TL;DR: In this paper, the effects of loading and modification of the resin on the physical, mechanical, thermal, and morphological properties of the bamboo reinforced modified polypropylene composites were studied.
Abstract: Short bamboo fiber reinforced polypropylene composites were prepared by incorporation of various loadings of chemically modified bamboo fibers. Maleic anhydride grafted polypropylene (MA-g-PP) was used as compatibilizer to improve fiber–matrix adhesion. The effects of bamboo fiber loading and modification of the resin on the physical, mechanical, thermal, and morphological properties of the bamboo reinforced modified PP composites were studied. Scanning electron microscopy studies of the composites were carried out on the interface and fractured surfaces. Thermogravimetric analysis and IR spectroscopy were also carried out. At 50% volume fraction of the extracted bamboo fiber in the composites, considerable increase in mechanical properties like impact, flexural, tensile, and thermal behavior like heat deflection temperature were observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
177 citations
Book•
01 Jan 2011
TL;DR: In this paper, the structure and properties of fiber-based composites have been investigated for composite applications in the context of non-conventional sources, such as natural fiber reinforcement.
Abstract: Part I Cellulose Fibers and Nanofibers 1. Natural Fibers: Structure, Properties and Applications S. Thomas, S.A. Paul, L.A. Pothan and Deepa B 2. Chemical Functionalization of Cellulose Derived from Non-conventional Sources V.K. Varshney and Sanjay Naithani 3. Production of Flax Fibers for Biocomposites Jonn Foulk, Danny Akin, Roy Dodd and Chad Ulven 4. Cellulosic Bast Fibers, Their Structure and Properties Suitable for Composite Applications Malgorzata Zimniewska, Maria Wladyka - Przybylak and Jerzy Mankowski 5. Potential Use of Micro- and Nanofibrillated Cellulose Composites Exemplified by Paper Ramjee Subramanian, Eero Hiltunen and Patrick A.C. Gane Part II Cellulosic Fiber Reinforced Polymer Compo-sites and Nanocomposites 6. Greener Surface Treatments of Natural Fiber Rein-forcements for use in the Production of Composite Mate-rials Koon-Yang Lee, Anne Delille and Alexander Bismarck 7. Nanocellulose Based Composites Kelley Spence, Youssef Habibi and Alain Dufresne 8. Dimensional Analysis and Surface Morphology as Selective Criteria of Lignocellulosic Fibers as Reinforcement in Polymeric Matrices Kestur G Satyanarayana, Sergio N Monteiro, Felipe Perisse D Lopes, Frederico M Margem, Helvio P G Santafe Jr. and Lucas L da Costa 9. Interfacial Shear Strength in Lignocellulosic Fibers In-corporated Polymeric Composites Sergio Neves Monteiro, Kestur G. Satyanarayana, Frederico Muylaert Margem, Ailton da Silva Ferreira, Denise Cristina Oliveira Nascimeto, Helvio Pessanha Guimaraes Santafe Jr and Felipe Perisse Duarte Lopes 10. The Structure, Morphology and Mechanical Properties of Thermoplastic Composites with Fiber and Energetic Plants Slawomir Borysiak, Dominik Paukszta, Paulina Batkowska and Jerzy Mankowski 11. Isora Fiber- A Natural Reinforcement for the Develop-ment of High Performance Engineering Materials Lovely Mathew, M.K. Joshy and Rani Joseph 12. Pineapple Leaf Fibers (PALF) and PALF-Reinforced Po-lymer Composites Mohd Sapuan Salit, Mohamed Abdul Rahman, Januar Parlaungan Siregar and Mohamad Ridzwan Ishak 13. Utilization of Rice Husks and the Products of its Degra-dation as Fillers of Polymer Composites S. D. Genieva, S. Ch. Turmanova and L. T. Vlaev 14. Polyolefin Based Natural Fiber Composites Santosh D Wanjale and Jyoti P Jog 15. All Cellulosic-based Composites J. P. Borges, M. H. Godinho, J. L. Figueirinhas, M. N. de Pinho and M.N. Belgacem Part III Biodegradable Plastics & Composites from Re-newable Resources 16. Environment Benevolent Biodegradable Polymers: Syn-thesis, Biodegradability and Applications B.S. Kaith, Hemant Mittal, Rajeev Jindal, Mithu Maiti and Susheel Kalia 17. Biocomposites based on Biodegradable Thermoplastic Polyester and Ligno-cellulose Fibers Luc Averous 18. Man-made Cellulose Short Fiber Reinforced Oil and Bio-based Thermoplastics Johannes Ganster and Hans-Peter Fink 19. Degradation of Cellulose Based Polymer Composites J.K. Pandey, D.R. Saini and S.H. Ahn 20. Biopolymeric Nanocomposites as Environment benign Materials Pratheep Kumar Annamalai and Raj Pal Singh Part IV Applications of Cellulose Fiber Reinforced Po-lymer Composites 21. Cellulose Nanocomposites for High Performance Appli-cations Bibin Mathew Cherian, Alcides Lopes Leao, Sivoney Ferreira de Souza, Sabu Thomas, Laly A Pothan and M Kottaisamy 22. Sisal Fiber Based Polymer Composites and their Applica-tions Mohini Saxena, Asokan Pappu, Ruhi Haque and Anusha Sharma 23. Natural Fiber-Reinforced Polymer Composites and Na-nocomposites for Automotive Applications James Njuguna, Paul Wambua, Krzysztof Pielichowski and Kambiz Kayvantash 24. Natural Fiber Based Composite Building Materials B. Singh, M. Gupta, Hina Tarannum and Anamika Randhawa
163 citations
TL;DR: In this paper, a new set of natural fiber based polymer composites consisting of coconut coir as reinforcement and epoxy resin as matrix material are described with respect to their mechanical characteristics.
Abstract: Fiber reinforced polymer composites have played a dominant role for a long time in a variety of applications for their high specific strength and modulus. The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. To this end, an investigation has been carried out to make use of coir, a natural fiber abundantly available in India. Natural fibers are not only strong and lightweight but also relatively very cheap. The present work describes the development and characterization of a new set of natural fiber based polymer composites consisting of coconut coir as reinforcement and epoxy resin as matrix material. The developed composites are characterized with respect to their mechanical characteristics. Experiments are carried out to study the effect of fiber length on mechanical behavior of these epoxy based polymer composites. Finally, the scanning electron microscope (SEM) of fractured surfaces has been done to study their surface morphology.
TL;DR: In this article, a surface treatment based on 3-aminopropyltriethoxysilane (APS) was performed to enhance the compatibility of the cellulose fibers with PLA matrix.
Abstract: Polymer composites from polylactic acid (PLA) and two types of cellulose fibers obtained either by acid hydrolysis of microcrystalline cellulose (HMCC) or by mechanical disintegration of regenerated wood fibers (MF) were prepared and characterized. To enhance the compatibility of the cellulose fibers with PLA matrix, a surface treatment based on 3-aminopropyltriethoxysilane (APS) was performed. The Fourier Transform Infrared (FTIR) spectroscopy was used to determine the chemical groups involved in the surface modification reaction. The silanization treatment resulted in different modifications on both types of cellulose fibers because of their different structural and morphological characteristics. The composites were prepared by incorporating 2.5% of the treated or untreated HMCC and MF into a PLA matrix using a melt-compounding technique. An improved adhesion between the two phases of the composite materials was observed by scanning electron microscopy thanks to treatment. The dynamic mechanical thermal analyses showed that both untreated and silane treated fibers led to an improvement of the storage modulus of PLA in the glassy state. A higher enhancement of the storage modulus in the case of PLA/HMCC composites than the composites containing MF was obtained as a result of the high aspect ratio of these fibers which allows better matrix-to-filler stress transfer. Furthermore, the storage modulus of PLA composites was enhanced by silanization even at higher temperatures especially after thermal treatment. The cellulose fibers addition in PLA matrix modified significantly the relaxation phenomenon as observed in tan δ curves, emphasizing strongly modified molecular mobility of PLA macromolecules and crystallization changes. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers.
TL;DR: The effect of fiber lignin content on biocomposite properties was investigated in this paper, which showed that the addition of coconut coir fiber significantly improved properties of wheat gluten biomaterials.
Abstract: The effect of fiber lignin content on biocomposite properties was investigated. Coconut fiber was treated with 0.7% sodium chlorite to selectively decrease amounts of lignin. The fiber lignin content was then reduced from 42 to 21 wt.%. The composition and mechanical properties of the individual modified fibers were characterized. Gluten-based materials reinforced with modified fibers were prepared by compression molding. Then, the mechanical properties, water sensibility, matrix glass transition and infrared spectra of biocomposites prepared with fibers containing various amounts of lignin were evaluated. This study showed that the addition of coconut coir fiber significantly improved properties of wheat gluten biomaterials. In addition, the variation of lignin content in the fibers, in the investigated range, had no significant effect neither on matrix deplasticization nor fiber/matrix adhesion, suggesting that a partial lignin removal is not an efficient way to improve the properties of natural fiber/plasticized protein biocomposites.
TL;DR: In this article, a comparative study of biomass fiber-reinforced polypropylene composite systems was performed, which showed that for equal amounts of (30%) biomass fibers, tensile and flexural modulii of PHBV composites showed much higher values than corresponding PP composites.
TL;DR: In this paper, surface modification of jute fibers was accomplished by performing chemical treatments, including detergent washing, dewaxing, alkali, and acetic acid treatment, which revealed improved surfaces for better adhesion with matrix.
Abstract: Surface modification of jute fibers was accomplished by performing chemical treatments, including detergent washing, dewaxing, alkali, and acetic acid treatment. Morphology of modified surfaces examined using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) revealed improved surfaces for better adhesion with matrix. Enhanced tensile properties of treated fibers were obtained from fiber bundle tensile tests. Using solution intercalation technique and magnetic stirring, 2%, 3%, and 4% by weight Montmorillonite K10 nanoclay were dispersed into the biodegradable polymer, biopol. Jute fiber reinforced biopol biocomposites with and without nanoclay manufactured using treated and untreated fibers by compression molding process showed almost the same volume fraction for all the samples. However, the lower void content was observed in the surface modified and nanoclay infused jute biopol composites. Mechanical responses of treated fiber reinforced biopol composites (TJBC) without nanoclay evaluated using dynamic mechanical analysis (DMA) and flexure tests showed 9% and 12% increase in storage modulus and flexure strength, respectively, compared to untreated jute fiber reinforced composites (UTJBC). The respective values were 100% and 35% for 4% nanoclay infused TJBC, compared to UTJBC without nanoclay. Lower moisture absorption and better mechanical properties were found in the nanophased composites even after moisture conditioning.
TL;DR: In this article, the effect of water absorption behavior on the dynamic mechanical properties of pultruded kenaf fiber reinforced composites (PKRC) was investigated by immersing PKRC specimens into three different conditions at room temperature for a period of 24 weeks.
Abstract: This paper reports the effect of water absorption behavior on the dynamic mechanical properties of pultruded kenaf fiber reinforced composites (PKRC). Water absorption tests were conducted by immersing PKRC specimens into three different conditions at room temperature for a period of 24 weeks. Water absorption curves with diffusion coefficient (D), maximum moisture content, Mm and permeability coefficient, P were determined. The dynamic mechanical property of PKRC was found to be highly affected by the presence of absorbed water in the specimens. Morphological study using Field Emission Scanning Electron Microscope (FESEM) reveals that the fiber is highly exposed to the solution after 24 weeks of immersion.
TL;DR: In this paper, maleic anhydride grafted polypropylene and hemp fiber composites were prepared by melt compounding, followed by injection molding, and then they were used to construct composite materials.
Abstract: Polypropylene and hemp fiber composites were prepared by melt compounding, followed by injection molding. Maleic anhydride grafted polypropylene (PP—MAH), maleic anhydride grafted styrene—(ethylene...
TL;DR: In this paper, the properties of films based on xylan reinforced with several cellulosic resources including nanocrystalline cellulose, acacia bleached kraft pulp fibers and softwood kraft fibers have been evaluated.
TL;DR: In this article, the use of natural fibers as reinforcement in polymeric composites for technical applications has been a research subject of scientists during the last decade, motivated by potential advantages of weight saving, lower raw material price, and ecological advantages of using green resources which are renewable and biodegradable.
TL;DR: In this paper, rice straw fiber (RSF) was pre-treated with PMMA thin film to improve its compatibility with PLA, and the results showed that the tensile strength of TRSF-PLA composites increased significantly at all contents (10, 20, 30% v/v).
TL;DR: In this article, the relationship between the material parameters, i.e., the fiber fineness, porosity, areal density, layering sequence, and airflow resistivity with the normal- incidence sound absorption coefficient of nonwoven com- posites consisting of three layers have been studied.
Abstract: The relationships between the material parameters, i.e., the fiber fineness, porosity, areal density, layering sequence, and airflow resistivity with the normal- incidence sound absorption coefficient of nonwoven com- posites consisting of three layers have been studied. The monofiber or multifiber needle-punched nonwovens included poly(lactic acid) (PLA), polypropylene (PP), glass fiber, and hemp fibers. Air flow resistivity was statistically modeled and was found to increase with decreasing fiber size and nonwoven porosity. The former models devel- oped for glass fiber mats in the literature were found to be inconsistent with the air flow resistance of the nonwovens reported below. The effects of the layering sequence on air flow resistivity and sound absorption were obtained. It was found that when the layer including reinforcement fibers, i.e., hemp or glass fiber, faced the air flow/sound source, the air flow resistance and the absorption coeffi- cient were higher than the case when the layer including reinforcement fibers was farthest from the air flow/sound source. The difference was more pronounced if there was a greater difference between the resistivity values of the constituent layers of the nonwoven composite. Sound absorption coefficient was statistically modeled in terms of air flow resistivity and frequency. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3056-3069, 2011
01 Jan 2011
TL;DR: In this article, the mechanical properties of natural fiber composites were evaluated and the results showed that as the fiber volume fraction and composite post-curing time increases, the properties of the composite increases.
Abstract: Natural Fibers composites are considered to have po tential use as reinforcing material in polymer matr ix composites because of their good strength, stiffnes s, low cost, environmental friendly and biodegradab le. In present study, mechanical properties for natural fi ber composites were evaluated. Here, areca fiber is used as new natural fiber reinforcement and epoxy resin as matrix. The extracted areca fibers from areca hu sk were chemically treated to get better interfacial b onding between fiber and matrix. Composite were prepared with randomly orientated fibers with diffe rent proportions of fibers and matrix ratio. Mechan ical tests i.e. impact and hardness tests were performed and the results are reported. The results showed t hat, as the fiber volume fraction and composite post curing time increases the mechanical properties of the composite increases.
TL;DR: In this article, the composites have comparable strength to structural lumber and engineered wood products, with stiffness comparable to most engineered wood product, and simple nonlinear models using laminate plate theory and uncoupled ply-level experimental constitutive response are evaluated.
Abstract: Biobased composites are being evaluated for construction applications where wood or petroleum-based composites are currently used. The biobased composites studied are made from biopolymers and plant-based fibers and have been demonstrated to rapidly biodegrade in anaerobic conditions to methane thereby reducing construction-related landfill waste and producing a useful end product, namely fuel for energy or feedstock to grow more biopolymer. Mechanical properties are evaluated for hemp fabric/cellulose acetate and hemp fabric/poly(hydroxybutyrate) (PHB) composites. The composites have comparable strength to structural lumber and engineered wood products, with stiffness comparable to most engineered wood products. Classical laminate plate theory sufficiently predicts initial laminate behavior from ply-level experimental data. Simple nonlinear models using laminate plate theory and uncoupled ply-level experimental constitutive response are evaluated.
TL;DR: In this article, the tensile, flexural, and impact properties of hybridized kenaf/PALF-reinforced HDPE composite were studied, and a notched Izoid impact test was conducted using a 1-J universal pendulum according to ASTM D256.
Abstract: Hybridization, especially where only variant natural lignocelluloses are combined, is fast receiving encouraging attention because it offers a range of properties that may be difficult to obtain with a single kind of reinforcement. In this study, tensile, flexural, and impact properties of hybridized kenaf/PALF-reinforced HDPE composite were studied. Sheets from which tensile, flexural, and impact specimens were cut out were produced from the compression molding of composite pellets and subsequently conditioned in an oven for 21 h at 103°C. The tensile and flexural specimens were tested according to ASTM D638 and ASTM D790 using a 5-kN INSTRON bluehill universal testing machine accordingly. While a notched Izoid impact test was conducted using a 1-J universal pendulum according to ASTM D256. All specimens were prepared at a fiber ratio of 1:1 kenaf:PALF and fiber lengths of 0.25, 0.5, 0.75, and 2 mm; fiber loadings of between 10% and 70% were utilized for the study. About 0.25 mm fiber showed the best ten...
TL;DR: In this article, the flexural properties of abaca-reinforced polypropylene composites have been studied and their flexural mechanical properties have been compared with composites reinforced with fiberglass.
TL;DR: In this article, raw and oxidized wool fabrics were treated with nano titanium dioxide (TiO2) powder in an ultrasonic bath and the results showed that increasing the amount of nano TiO2 leads to improved degradation of stains on the treated fabric.
Abstract: Wool is a textile material that is valued for its strength, warmth, water resistance, and texture. But this natural fiber of the protein keratin lacks the stain resistance of synthetic fabrics and is also generally susceptible to harsh processing conditions. In this study, raw and oxidized wool fabrics were treated with nano titanium dioxide (TiO2) powder in an ultrasonic bath. These particles were linked to the wool surface by butane tetra carboxylic acid and also sodium hypophosphite was used as a catalyst. The photo‐catalytic activity of TiO2 nanoparticles deposited on the wool fabrics was followed by the degradation of Acid Blue 113 as a stain and also determined by the degradation rate of food stains such as coffee, tea, and fruit juice under the ultraviolet rays. The results showed that increasing the amount of nano TiO2 leads to improved degradation of stains on the treated fabric.
TL;DR: The results showed that 20 wt % glycerol was sufficient for plasticization, yielding foams with low modulus and high strain recovery, and when fibers were mixed into the foams, a small but insignificant increase in elastic modulus was achieved, and the foam structure became more homogeneous.
TL;DR: In this paper, changes in molecular weight and secondary structure of eri silk during alkali degumming and silk powdering were studied, and it was shown that the conformation remained essentially β-sheet even in the sub-micron silk particles.
Abstract: Changes in molecular weight and secondary structure of eri silk during alkali degumming and silk powdering were studied. An increase in silk degumming intensity, through increased alkali concentration, treatment temperature, and time, reduced the fibroin molecular weight and, therefore, the fiber tenacity, but at the same time, increased the β-sheet fraction. These changes reduced the time required to mill the degummed silk fibers into fine powders. Mechanical forces used in wet attritor and air jet milling disturbed intermolecular packing along the direction of side chains, but the conformation remained essentially β-sheet even in the sub-micron silk particles. Dry milling drastically reduced molecular weight and changed the conformation of the fibroin chains. The rate of the spontaneous conformation transition in regenerated fibroin solution prepared from fibers and powders increased with a decrease in fibroin molecular weight, affecting the time fibroin solutions could be stored before gelling. Overall, the study showed that molecular weight and secondary structure of silk powders could be manipulated by suitably changing the degumming and milling conditions. It also suggests that wet media milling and air jet milling are better than dry media milling to prepare less degraded and more crystalline ultrafine silk particles.
TL;DR: In this paper, the authors developed composites from wheat gluten using water as a plasticizer without any chemicals and showed that water is an effective plasticizer for wheat gluten and could be used to develop various types of inexpensive and biodegradable wheat gluten-based thermoplastics.
Abstract: Biocomposites developed from wheat gluten using water without any chemicals as plasticizer and jute fibers as reinforcement have much bet ter flexural and tensile properties than similar polypropylene composites reinforced with jute fibers. Wheat gluten is an inexpensive and abun dant co-product derived from renewable resources and is biodegradable but non-thermoplastic. Previous attempts at developing biocomposites from wheat gluten have used plasticizers such as glycerol or chemical modifications to make gluten thermoplastic. However, plasticizers have a considerably negative effect on the mechanical properties of the composites and chemical modifications make wheat gluten less biode gradable, expensive and/or environmentally unfriendly. In the research reported, we developed composites from wheat gluten using water as a plasticizer without any chemicals. Water plasticizes wheat gluten but evaporates during compression molding and therefore does not affect the mechanical properties of the composites. The effect of composite fabrication conditions on the flexural, tensile and acoustic properties was studied in comparison to polypropylene composites reinforced with jute fibers. Wheat gluten composites had flexural strength (20 MPa), tensile strength (69 MPa) and tensile modulus (7.7 GPa) values approximately twice those of polypropylene composites. Water is an effective plasticizer for wheat gluten and could be used to develop various types of inexpensive and biodegradable wheat gluten-based thermoplastics.
TL;DR: In this paper, a statistical strength model of continuous UD fiber reinforced composites is applied to assess the upper limit of tensile strength of such slightly misoriented, nominally UD natural fiber composite, and it is found that the experimental strength of UD flax composites, produced from rovings or manually aligned fibers, approaches the theoretical limit only at relatively low fiber volume fraction ca 0.2, being markedly below it at higher fiber content.
Abstract: Unidirectional orientation of natural fibers in a polymer composite ensures the highest efficiency of reinforcement. Flax fiber reinforcement is discontinuous due to limited fiber length and heterogeneous due to the presence of elementary fibers and their bundles. In order to assess the upper limit of tensile strength of such slightly misoriented, nominally UD natural fiber composite, a statistical strength model of continuous UD fiber reinforced composites is applied. It is found that the experimental strength of UD flax composites, produced from rovings or manually aligned fibers, approaches the theoretical limit only at relatively low fiber volume fraction ca. 0.2, being markedly below it at higher fiber content.