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Polymers
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Natural Fibres and their Composites II
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Natural Fibres and their Composites II

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Composites and Nanocomposites".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 49463

Special Issue Editors

Prof. Dr. Vincenzo Fiore

E-Mail Website
Guest Editor
Department of Engineering, University of Palermo, Viale delle Scienze ed.6, 90128 Palermo, Italy
Interests: natural fibres; polymer composites; biobased materials; hybrid composites; fiber-matrix adhesion; structural joints; mechanical properties
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Fabrizio Sarasini

E-Mail Website
Guest Editor
Department of Chemical Engineering Materials Environment, University of Rome La Sapienza, 00184 Roma, Italy
Interests: fibre/matrix interfacial modification and assessment; use of plant fibres in biopolymers (biodegradable or from renewable resources) for designing biocomposites with reduced environmental impact; combination of natural fibres (mineral and vegetal) in hybrid composites for designing sustainable composites for semi-structural applications; valorization of agro-industrial wastes as fillers in thermoplastic matrices (micro- and nanoscale); durability of composite materials based on thermoplastic and thermoset matrices
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

An increasing interest in environmentally friendly fibre reinforced composites (i.e., derived from materials coming from renewable resources) has been recorded over the past few decades, due to our global awareness of environmental issues. In this context, natural fibres from different bio-renewable resources (i.e., vegetable, mineral and animal ones) have attracted great attention, both from academia and from several industrial fields, thanks to their specific properties, low price, great availability, health advantages, easy processing, renewability, biodegradability and recyclability.

This Special Issue aims to update the state-of-the-art and the developments made in the field of natural fibres and their composites, including, but not limited to, the following aspects:

  • Fibre extraction and retting processes;
  • Fibre properties’ characterisation;
  • Fibre treatments;
  • Composites’ manufacturing processes;
  • Composites’ properties characterisation;
  • Composites’ aging resistance evaluation.

Original research and review papers are invited for this Special Issue.

Prof. Dr. Vincenzo Fiore
Prof. Dr. Fabrizio Sarasini
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • natural fibres
  • polymer composites
  • bio-based materials
  • hybrid composites
  • fibre–matrix adhesion

Published Papers (16 papers)

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17 pages, 3257 KiB  
Article
Effect of Glass Fiber Hybridization on the Durability in Salt-Fog Environment of Pinned Flax Composites
by Vincenzo Fiore and Luigi Calabrese
Polymers 2021, 13(23), 4201; https://doi.org/10.3390/polym13234201 - 30 Nov 2021
Cited by 7 | Viewed by 1823
Abstract
The aim of the present paper is to evaluate the effect of the hybridization with external layers of glass fibers on the durability of flax fiber reinforced composites in severe aging conditions. To this scope, full glass, full flax and hybrid glass–flax pinned [...] Read more.
The aim of the present paper is to evaluate the effect of the hybridization with external layers of glass fibers on the durability of flax fiber reinforced composites in severe aging conditions. To this scope, full glass, full flax and hybrid glass–flax pinned laminates were exposed to a salt-fog environment for up to 60 days. Double-lap pinned joint tests were performed to assess the pin-hole joints performances at varying the laminate stacking sequence. In order to better discriminate the relationship between the mechanical behavior and the fracture mechanisms of joints at increasing the aging time, different geometries (i.e., by varying both the hole diameter D and the free edge distance from the center of the hole E) were investigated after 0 (i.e., unaged samples), 30 and 60 days of salt-fog exposition. It was shown that the hybridization positively affects the mechanical performance as well as the stability of pinned composites: i.e., improvements in both strength and durability against the salt-fog environment were evidenced. Indeed, the hybrid laminate exhibited a reduction in the bearing strength of about 20% after 60 days of aging, despite to full flax laminate, for which a total reduction in the bearing strength of 29% was observed. Finally, a simplified joint failure map was assessed, which clusters the main failure mechanisms observed for pinned composites at varying aging conditions, thus assisting the joining design of flax–glass hybrid laminates. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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16 pages, 9508 KiB  
Article
Use of Biochar as Filler for Biocomposite Blown Films: Structure-Processing-Properties Relationships
by Luigi Botta, Rosalia Teresi, Vincenzo Titone, Giusi Salvaggio, Francesco Paolo La Mantia and Francesco Lopresti
Polymers 2021, 13(22), 3953; https://doi.org/10.3390/polym13223953 - 16 Nov 2021
Cited by 22 | Viewed by 2680
Abstract
In this work, biocomposite blown films based on poly(butylene adipate-co-terephthalate) (PBAT) as biopolymeric matrix and biochar (BC) as filler were successfully fabricated. The materials were subjected to a film-blowing process after being compounded in a twin-screw extruder. The preliminary investigations conducted on melt-mixed [...] Read more.
In this work, biocomposite blown films based on poly(butylene adipate-co-terephthalate) (PBAT) as biopolymeric matrix and biochar (BC) as filler were successfully fabricated. The materials were subjected to a film-blowing process after being compounded in a twin-screw extruder. The preliminary investigations conducted on melt-mixed PBAT/BC composites allowed PBAT/BC 5% and PBAT/BC 10% to be identified as the most appropriate formulations to be processed via film blowing. The blown films exhibited mechanical performances adequate for possible application as film for packaging, agricultural, and compost bags. The addition of BC led to an improvement of the elastic modulus, still maintaining high values of deformation. Water contact angle measurements revealed an increase in the hydrophobic behavior of the biocomposite films compared to PBAT. Additionally, accelerated degradative tests monitored by tensile tests and spectroscopic analysis revealed that the filler induced a photo-oxidative resistance on PBAT by delaying the degradation phenomena. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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16 pages, 2999 KiB  
Article
Enhanced Mechanical and Thermal Properties of Modified Oil Palm Fiber-Reinforced Polypropylene Composite via Multi-Objective Optimization of In Situ Silica Sol-Gel Synthesis
by Nasrullah Mat Rozi, Hamidah Abdul Hamid, Md. Sohrab Hossain, Nor Afifah Khalil, Ahmad Naim Ahmad Yahaya, Ahmad Noor Syimir Fizal, Mohd Yusoff Haris, Norkhairi Ahmad and Muzafar Zulkifli
Polymers 2021, 13(19), 3338; https://doi.org/10.3390/polym13193338 - 29 Sep 2021
Cited by 4 | Viewed by 1668
Abstract
A multi-objective optimization of in situ sol-gel process was conducted in preparing oil palm fiber-reinforced polypropylene (OPF-PP) composite for an enhancement of mechanical and thermal properties. Tetraethyl orthosilicate (TEOS) and butylamine were used as precursors and catalysts for the sol-gel process. The face-centered [...] Read more.
A multi-objective optimization of in situ sol-gel process was conducted in preparing oil palm fiber-reinforced polypropylene (OPF-PP) composite for an enhancement of mechanical and thermal properties. Tetraethyl orthosilicate (TEOS) and butylamine were used as precursors and catalysts for the sol-gel process. The face-centered central composite design (FCCD) experiments coupled with response surface methodology (RSM) has been utilized to optimize in situ silica sol-gel process. The optimization process showed that the drying time after the in-situ silica sol-gel process was the most influential factor on silica content, while the molar ratio of TEOS to water gave the most significant effect on silica residue. The maximum silica content of 34.1% and the silica residue of 35.9% were achieved under optimum conditions of 21.3 h soaking time, 50 min drying time, pH value of 9.26, and 1:4 molar ratio of TEOS to water. The untreated oil palm fiber (OPF) and silica sol-gel modified OPF (SiO2-OPF) were used as the reinforcing fibers, with PP as a matrix and maleic anhydride grafted polypropylene (MAgPP) as a compatibilizer for the fiber-reinforced PP matrix (SiO2-OPF-PP-MAgPP) composites preparation. The mechanical and thermal properties of OPF-PP, SiO2-OPF-PP, SiO2-OPF-PP-MAgPP composites, and pure PP were determined. It was found that the OPF-S-PP-MAgPP composite had the highest toughness and stiffness with values of tensile strength, Young’s modulus, and elongation at break of 30.9 MPa, 881.8 MPa, and 15.1%, respectively. The thermal properties analyses revealed that the OPF-S-PP-MAgPP exhibited the highest thermally stable inflection point at 477 °C as compared to pure PP and other composites formulations. The finding of the present study showed that the SiO2-OPF had the potential to use as a reinforcing agent to enhance the thermal-mechanical properties of the composites. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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14 pages, 4850 KiB  
Article
Extraction of Cellulose Polymeric Material from Populus tremula Fibers: Characterization and Application to the Adsorption of Methylene Blue and Crystal Violet
by Faisal Muteb Almutairi, Yassine El-Ghoul and Mahjoub Jabli
Polymers 2021, 13(19), 3334; https://doi.org/10.3390/polym13193334 - 29 Sep 2021
Cited by 14 | Viewed by 1872
Abstract
Cellulose is the most widely available biopolymer which is extensively used for several applications including textiles, composites, pharmaceutical, water treatment, etc. In this investigation, cellulose was chemically extracted from Populus tremula seed fibers. Samples were characterized using FT-IR, SEM, XRD, and TGA-DTA analyses. [...] Read more.
Cellulose is the most widely available biopolymer which is extensively used for several applications including textiles, composites, pharmaceutical, water treatment, etc. In this investigation, cellulose was chemically extracted from Populus tremula seed fibers. Samples were characterized using FT-IR, SEM, XRD, and TGA-DTA analyses. FT-IR spectrum of the extracted cellulose confirmed that hemicellulose and lignin were removed during alkali and bleaching treatments. SEM images showed the partially roughened surface of the fiber due to the removal of non-cellulosic elements and surface impurities during chemical modification. The crystallinity index values for untreated Populus tremula fibers and extracted cellulose were calculated to be 32.8% and 58.9%, respectively. The obvious increase in the crystallinity index for the extracted cellulose confirmed the removal of amorphous compounds present in raw populus. Alkali-treated populus fibers were more thermally stable than raw fibers. All changes observed after alkali and bleaching treatments evidenced the removal of amorphous contents and non-cellulosic components in raw populus fibers. Extracted cellulose exhibited excellent adsorption capacities of methylene blue (140.4 mg g−1) and crystal violet (154 mg g−1). The pseudo second order equation fitted well the kinetic data indicating a chemi-sorption process. The Freundlich model complied well with the experimental data suggesting that the adsorption of the studied dyes was multilayer. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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13 pages, 12461 KiB  
Article
PBAT Based Composites Reinforced with Microcrystalline Cellulose Obtained from Softwood Almond Shells
by Luigi Botta, Vincenzo Titone, Maria Chiara Mistretta, Francesco Paolo La Mantia, Aurora Modica, Maurizio Bruno, Francesco Sottile and Francesco Lopresti
Polymers 2021, 13(16), 2643; https://doi.org/10.3390/polym13162643 - 09 Aug 2021
Cited by 20 | Viewed by 3615
Abstract
This study explores the processability, mechanical, and thermal properties of biocompostable composites based on poly (butylene adipate-co-terephthalate) (PBAT) as polymer matrix and microcrystalline cellulose (MCC) derived from softwood almond (Prunus dulcis) shells (as-MCC) as filler at two different weight concentration, i.e., [...] Read more.
This study explores the processability, mechanical, and thermal properties of biocompostable composites based on poly (butylene adipate-co-terephthalate) (PBAT) as polymer matrix and microcrystalline cellulose (MCC) derived from softwood almond (Prunus dulcis) shells (as-MCC) as filler at two different weight concentration, i.e., 10 wt% and 20 wt%. The materials were processed by melt mixing and a commercial MCC (c-MCC) was used as filler comparison. The fibrillar shape of as-MCC particles was found to change the rheological behavior of PBAT, particularly at the highest concentration. The melt mixing processing allowed obtaining a uniform dispersion of both kinds of fillers, slightly reducing the L/D ratio of as-MCC fibers. The as-MCC particles led to a higher increase of the elastic modulus of PBAT if compared to the c-MCC counterparts. Both the MCC fillers caused a drastic reduction of the elongation at break, although it was higher than 120% also at the highest filler concentrations. DSC analysis revealed that both MCC fillers poorly affected the matrix crystallinity, although as-MCC induced a slight PBAT crystallinity increase from 8.8% up to 10.9% for PBAT/as-MCC 20%. Therefore, this work demonstrates the great potential of MCC particles derived from almond shells as filler for biocompostable composites fabrication. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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12 pages, 13305 KiB  
Article
Investigations by AFM of Ageing Mechanisms in PLA-Flax Fibre Composites during Garden Composting
by Alessia Melelli, Delphin Pantaloni, Eric Balnois, Olivier Arnould, Frédéric Jamme, Christophe Baley, Johnny Beaugrand, Darshil U. Shah and Alain Bourmaud
Polymers 2021, 13(14), 2225; https://doi.org/10.3390/polym13142225 - 06 Jul 2021
Cited by 9 | Viewed by 2586
Abstract
PLA-flax non-woven composites are promising materials, coupling high performance and possible degradation at their end of life. To explore their ageing mechanisms during garden composting, microstructural investigations were carried out through scanning electron microscopy (SEM) and atomic force microscopy (AFM). We observe that [...] Read more.
PLA-flax non-woven composites are promising materials, coupling high performance and possible degradation at their end of life. To explore their ageing mechanisms during garden composting, microstructural investigations were carried out through scanning electron microscopy (SEM) and atomic force microscopy (AFM). We observe that flax fibres preferentially degrade ‘inwards’ from the edge to the core of the composite. In addition, progressive erosion of the cell walls occurs within the fibres themselves, ‘outwards’ from the central lumen to the periphery primary wall. This preferential degradation is reflected in the decrease in indentation modulus from around 23 GPa for fibres located in the preserved core of the composite to 3–4 GPa for the remaining outer-most cell wall crowns located at the edge of the sample that is in contact with the compost. Ageing of the PLA matrix is less drastic with a relatively stable indentation modulus. Nevertheless, a change in the PLA morphology, a significant decrease in its roughness and increase of porosity, can be observed towards the edge of the sample, in comparison to the core. This work highlights the important role of intrinsic fibre porosity, called lumen, which is suspected to be a major variable of the compost ageing process, providing pathways of entry for moisture and microorganisms that are involved in cell wall degradation. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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15 pages, 6338 KiB  
Article
Biocomposites of Low-Density Polyethylene Plus Wood Flour or Flax Straw: Biodegradation Kinetics across Three Environments
by Anna K. Zykova, Petr V. Pantyukhov, Elena E. Mastalygina, Christian Chaverri-Ramos, Svetlana G. Nikolaeva, Jose J. Saavedra-Arias, Anatoly A. Popov, Sam E. Wortman and Matheus Poletto
Polymers 2021, 13(13), 2138; https://doi.org/10.3390/polym13132138 - 29 Jun 2021
Cited by 14 | Viewed by 2601
Abstract
The purpose of this study was to assess the potential for biocomposite films to biodegrade in diverse climatic environments. Biocomposite films based on polyethylene and 30 wt.% of two lignocellulosic fillers (wood flour or flax straw) of different size fractions were prepared and [...] Read more.
The purpose of this study was to assess the potential for biocomposite films to biodegrade in diverse climatic environments. Biocomposite films based on polyethylene and 30 wt.% of two lignocellulosic fillers (wood flour or flax straw) of different size fractions were prepared and studied. The developed composite films were characterized by satisfactory mechanical properties that allows the use of these materials for various applications. The biodegradability was evaluated in soil across three environments: laboratory conditions, an open field in Russia, and an open field in Costa Rica. All the samples lost weight and tensile strength during biodegradation tests, which was associated with the physicochemical degradation of both the natural filler and the polymer matrix. The spectral density of the band at 1463 cm−1 related to CH2-groups in polyethylene chains decreased in the process of soil burial, which is evidence of polymer chain breakage with formation of CH3 end groups. The degradation rate of most biocomposites after 20 months of the soil assays was greatest in Costa Rica (20.8–30.9%), followed by laboratory conditions (16.0–23.3%), and lowest in Russia (13.2–22.0%). The biocomposites with flax straw were more prone to biodegradation than those with wood flour, which can be explained by the chemical composition of fillers and the shape of filler particles. As the size fraction of filler particles increased, the biodegradation rate increased. Large particles had higher bioavailability than small spherical ones, encapsulated by a polymer. The prepared biocomposites have potential as an ecofriendly replacement for traditional polyolefins, especially in warmer climates. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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12 pages, 37986 KiB  
Article
Tribological Behavior of a Rubber-Toughened Wood Polymer Composite
by Valentina Mazzanti, Annalisa Fortini, Lorenzo Malagutti, Giulia Ronconi and Francesco Mollica
Polymers 2021, 13(13), 2055; https://doi.org/10.3390/polym13132055 - 23 Jun 2021
Cited by 4 | Viewed by 1835
Abstract
Wood polymer composites or WPCs are increasingly used as substitutes for natural wood in outdoor applications due to their better environmental sustainability and the consequent reduction in carbon footprint. In this paper, the presence of an elastomer used as a toughening agent (Santoprene [...] Read more.
Wood polymer composites or WPCs are increasingly used as substitutes for natural wood in outdoor applications due to their better environmental sustainability and the consequent reduction in carbon footprint. In this paper, the presence of an elastomer used as a toughening agent (Santoprene by Exxon Mobil) in a polypropylene-based WPC containing 50 wt % wood flour was investigated in terms of its tribological behavior by dry sliding wear tests. These were performed after two environmental pre-conditioning treatments, i.e., drying and water soaking. The ball-on-disk configuration under a constant load was chosen along two sliding distances. Dynamic mechanical thermal analyses were used to reveal the effect of the toughening agent on the storage modulus and damping factor of the composites. Results in terms of weight loss measurement and coefficient of friction were obtained, together with surface morphology analysis of the worn surfaces at the scanning electron microscope and 3D profilometer. An abrasive wear mechanism was identified, and it was shown that the toughening agent improved wear resistance after both pre-treatments. This beneficial effect can be explained by the increase in strain at break of the WPC containing the elastomer. On the other hand, the water soaking pre-treatment produced severe damage, and the loss of material cannot be completely compensated by the presence of the toughening agent. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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13 pages, 3934 KiB  
Article
Fracture Characteristics and Energy Dissipation of Textile Bamboo Fiber Reinforced Polymer
by Chun-Wei Chang and Feng-Cheng Chang
Polymers 2021, 13(4), 634; https://doi.org/10.3390/polym13040634 - 20 Feb 2021
Cited by 8 | Viewed by 2086
Abstract
The fracture theory of fiber-reinforced polymer (FRP) composites is complicated compared to that of homogeneous materials. Textile FRPs need to consider crimp, fiber off-axis and various weaving parameters in a two-dimensional scale, which makes research of failure and fracture difficult. The objective and [...] Read more.
The fracture theory of fiber-reinforced polymer (FRP) composites is complicated compared to that of homogeneous materials. Textile FRPs need to consider crimp, fiber off-axis and various weaving parameters in a two-dimensional scale, which makes research of failure and fracture difficult. The objective and main contribution of the present research lie in taking textile bamboo FRP as an example and using tools such as toughness, load and deflection curves analysis, energy analysis, and first-order derivative signals to establish the preliminary information needed for fracture theory. This is followed by observing the fracture characteristics of the material under bending. The identification of fracture modes, corresponding energy, and energy dissipation are all prerequisites for developing fracture models in the future. Differences in the direction of force, weaving method, and number of laminates will cause the amount and direction of fibers to vary, which makes the type and progression of fracture different. Combining signal analysis, fracture images and energy dissipation curves, there are different modes of fracture between various groups due to different energy storage forms and crack types, which ultimately lead to different energy dissipation behaviors. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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19 pages, 5133 KiB  
Article
An Innovative Treatment Based on Sodium Citrate for Improving the Mechanical Performances of Flax Fiber Reinforced Composites
by Vincenzo Fiore, Dionisio Badagliacco, Carmelo Sanfilippo, Riccardo Miranda and Antonino Valenza
Polymers 2021, 13(4), 559; https://doi.org/10.3390/polym13040559 - 13 Feb 2021
Cited by 9 | Viewed by 1880
Abstract
The goal of this paper is to evaluate the effectiveness of a cost-effective and eco-friendly treatment based on the use of sodium citrate (Na3C6H5O7) on the mechanical properties of flax fiber reinforced composites. To this [...] Read more.
The goal of this paper is to evaluate the effectiveness of a cost-effective and eco-friendly treatment based on the use of sodium citrate (Na3C6H5O7) on the mechanical properties of flax fiber reinforced composites. To this scope, flax fibers were soaked in mildly alkaline solutions of the sodium salt at different weight concentration (i.e., 5%, 10% and 20%) for 120 h at 25 °C. The modifications on fibers surface induced by the proposed treatment were evaluated through Fourier transform infrared analysis (FTIR), whereas scanning electron microscope (SEM) and helium pycnometer were used to obtain useful information about composites morphology. The effect of the concentration of the treating solution on the mechanical response of composites was determined through quasi-static tensile and flexural tests, Charpy impact tests and dynamical mechanical thermal (DMTA) tests. The results revealed that composites reinforced with flax fibers treated in 10% solution exhibit the best mechanical performances as well as the lowest void contents. SEM analysis supported these findings showing that, by treating fibers in solutions with concentration up to 10%, composites having better morphology can be manufactured, in comparison to untreated ones. Conversely, higher Na3C6H5O7 concentrations negatively affect both the morphology and the mechanical properties of composites. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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17 pages, 12789 KiB  
Article
Mechanical Properties of Natural-Fiber-Reinforced Biobased Epoxy Resins Manufactured by Resin Infusion Process
by Mauricio Torres-Arellano, Victoria Renteria-Rodríguez and Edgar Franco-Urquiza
Polymers 2020, 12(12), 2841; https://doi.org/10.3390/polym12122841 - 29 Nov 2020
Cited by 38 | Viewed by 3845
Abstract
This work deals with the manufacture and mechanical characterization of natural-fiber-reinforced biobased epoxy resins. Biolaminates are attractive to various industries because they are low-density, biodegradable, and lightweight materials. Natural fibers such as Ixtle, Henequen, and Jute were used as reinforcing fabrics for two [...] Read more.
This work deals with the manufacture and mechanical characterization of natural-fiber-reinforced biobased epoxy resins. Biolaminates are attractive to various industries because they are low-density, biodegradable, and lightweight materials. Natural fibers such as Ixtle, Henequen, and Jute were used as reinforcing fabrics for two biobased epoxy resins from Sicomin®. The manufacture of the biolaminates was carried out through the vacuum-assisted resin infusion process. The mechanical characterization revealed the Jute biolaminates present the highest stiffness and strength, whereas the Henequen biolaminates show high strain values. The rigid and semirigid biolaminates obtained in this work could drive new applications targeting industries that require lightweight and low-cost sustainable composites. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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11 pages, 4469 KiB  
Article
Tensile and Flexural Properties of Silica Nanoparticles Modified Unidirectional Kenaf and Hybrid Glass/Kenaf Epoxy Composites
by Napisah Sapiai, Aidah Jumahat, Mohammad Jawaid, Mohamad Midani and Anish Khan
Polymers 2020, 12(11), 2733; https://doi.org/10.3390/polym12112733 - 18 Nov 2020
Cited by 39 | Viewed by 2978
Abstract
This paper investigates the influence of silica nanoparticles on the mechanical properties of a unidirectional (UD) kenaf fiber reinforced polymer (KFRP) and hybrid woven glass/UD kenaf fiber reinforced polymer (GKFRP) composites. In this study, three different nanosilica loadings, i.e., 5, 13 and 25 [...] Read more.
This paper investigates the influence of silica nanoparticles on the mechanical properties of a unidirectional (UD) kenaf fiber reinforced polymer (KFRP) and hybrid woven glass/UD kenaf fiber reinforced polymer (GKFRP) composites. In this study, three different nanosilica loadings, i.e., 5, 13 and 25 wt %, and untreated kenaf fiber yarns were used. The untreated long kenaf fiber yarn was wound onto metal frames to produce UD kenaf dry mat layers. The silane-surface-treated nanosilica was initially dispersed into epoxy resin using a high-vacuum mechanical stirrer before being incorporated into the UD untreated kenaf and hybrid woven glass/UD kenaf fiber layers. Eight different composite systems were made, namely KFRP, 5 wt % nanosilica in UD kenaf fiber reinforced polymer composites (5NS-KFRP), 13% nanosilica in UD kenaf fiber reinforced polymer composites (13NS-KFRP), 25 wt % nanosilica in UD kenaf fiber reinforced polymer composites (25NS-KFRP), GKFRP, 5 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (5NS-GKFRP), 13 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (13NS-GKFRP) and 25 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (25NS-GKFRP). All composite systems were tested in tension and bending in accordance with ASTM standards D3039 and D7264, respectively. Based on the results, it was found that the incorporation of homogeneously dispersed nanosilica significantly improved the tensile and flexural properties of KFRP and hybrid GKFRP composites even at the highest loading of 25 wt % nanosilica. Based on the scanning electron microscopy (SEM) examination of the fractured surfaces, it is suggested that the silane-treated nanosilica exhibits good interactions with epoxy and the kenaf and glass fibers. Therefore, the presence of nanosilica in an epoxy polymer contributes to a stiffer matrix that, effectively, enhances the capability of transferring a load to the fibers. Thus, this supports greater loads and improves the mechanical properties of the kenaf and hybrid composites. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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16 pages, 22905 KiB  
Article
The Effect of Jackfruit Skin Powder and Fiber Bleaching Treatment in PLA Composites with Incorporation of Thymol
by Muhammad Najib Ahmad Marzuki, Intan Syafinaz Mohamed Amin Tawakkal, Mohd Salahuddin Mohd Basri, Siti Hajar Othman, Siti Hasnah Kamarudin, Ching Hao Lee and Abdan Khalina
Polymers 2020, 12(11), 2622; https://doi.org/10.3390/polym12112622 - 07 Nov 2020
Cited by 12 | Viewed by 4013
Abstract
Food packaging has seen a growth in the use of materials derived from renewable resources such as poly(lactic acid) (PLA). However, the initial costs to produce bioplastics are typically high. Tropical fruit waste as naturally sourced fibres, such as jackfruit skin, can be [...] Read more.
Food packaging has seen a growth in the use of materials derived from renewable resources such as poly(lactic acid) (PLA). However, the initial costs to produce bioplastics are typically high. Tropical fruit waste as naturally sourced fibres, such as jackfruit skin, can be used as a cost-reducing filler for PLA. The main objective in this study is to fabricate a low-cost natural fibre-reinforced polymer that potentially applies in packaging with the aid of bleaching treatment. The treatment shows a rougher surface fibre in Scanning electron microscopy (SEM) micrographs and it is expected to have better mechanical locking with the matrix, and this is found similar with a Fourier-transform infrared spectroscopy (FTIR) analysis. Unfortunately, fibre insertion does find low tensile performances, yet bleached-fibre composites improved its performance significantly. A similar situation was found in the thermal characterization where a low-thermal stability natural fibre composite has lower thermal behaviour and this increased with bleaching treatment. Besides, bleached-fibre composites have a longer service period. Besides, a 15 wt% thymol insertion inhibits the growth of Gram-positive bacteria in the composites and the non-treated fibre composite has better thymol effects. The 30 wt% of the bleached-fibre insertion composite has a high potential to reduce the cost of bioplastic products with minimum alterations of overall performances. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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21 pages, 4407 KiB  
Article
Thermal and Structural Analysis of Epoxidized Jatropha Oil and Alkaline Treated Kenaf Fiber Reinforced Poly(Lactic Acid) Biocomposites
by Siti Hasnah Kamarudin, Luqman Chuah Abdullah, Min Min Aung and Chantara Thevy Ratnam
Polymers 2020, 12(11), 2604; https://doi.org/10.3390/polym12112604 - 06 Nov 2020
Cited by 28 | Viewed by 2981
Abstract
New environmentally friendly plasticized poly(lactic acid) (PLA) kenaf biocomposites were obtained through a melt blending process from a combination of epoxidized jatropha oil, a type of nonedible vegetable oil material, and renewable plasticizer. The main objective of this study is to investigate the [...] Read more.
New environmentally friendly plasticized poly(lactic acid) (PLA) kenaf biocomposites were obtained through a melt blending process from a combination of epoxidized jatropha oil, a type of nonedible vegetable oil material, and renewable plasticizer. The main objective of this study is to investigate the effect of the incorporation of epoxidized jatropha oil (EJO) as a plasticizer and alkaline treatment of kenaf fiber on the thermal properties of PLA/Kenaf/EJO biocomposites. Kenaf fiber was treated with 6% sodium hydroxide (NaOH) solution for 4 h. The thermal properties of the biocomposites were analyzed using a differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It must be highlighted that the addition of EJO resulted in a decrease of glass transition temperature which aided PLA chain mobility in the blend as predicted. TGA demonstrated that the presence of treated kenaf fiber together with EJO in the blends reduced the rate of decomposition of PLA and enhanced the thermal stability of the blend. The treatment showed a rougher surface fiber in scanning electron microscopy (SEM) micrographs and had a greater mechanical locking with matrix, and this was further supported with Fourier-transform infrared spectroscopy (FTIR) analysis. Overall, the increasing content of EJO as a plasticizer has improved the thermal properties of PLA/Kenaf/EJO biocomposites. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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Review

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19 pages, 2334 KiB  
Review
Current State and Challenges of Natural Fibre-Reinforced Polymer Composites as Feeder in FDM-Based 3D Printing
by Nishata Royan Rajendran Royan, Jie Sheng Leong, Wai Nam Chan, Jie Ren Tan and Zainon Sharmila Binti Shamsuddin
Polymers 2021, 13(14), 2289; https://doi.org/10.3390/polym13142289 - 13 Jul 2021
Cited by 34 | Viewed by 4492
Abstract
As one of the fastest-growing additive manufacturing (AM) technologies, fused deposition modelling (FDM) shows great potential in printing natural fibre-reinforced composites (NFRC). However, several challenges, such as low mechanical properties and difficulty in printing, need to be overcome. Therefore, the effort to improve [...] Read more.
As one of the fastest-growing additive manufacturing (AM) technologies, fused deposition modelling (FDM) shows great potential in printing natural fibre-reinforced composites (NFRC). However, several challenges, such as low mechanical properties and difficulty in printing, need to be overcome. Therefore, the effort to improve the NFRC for use in AM has been accelerating in recent years. This review attempts to summarise the current approaches of using NFRC as a feeder for AM. The effects of fibre treatments, composite preparation methods and addition of compatibilizer agents were analysed and discussed. Additionally, current methods of producing feeders from NFRCs were reviewed and discussed. Mechanical property of printed part was also dependent on the printing parameters, and thus the effects of printing temperature, layer height, infill and raster angle were discussed, and the best parameters reported by other researchers were identified. Following that, an overview of the mechanical properties of these composites as reported by various researchers was provided. Next, the use of optimisation techniques for NFRCs was discussed and analysed. Lastly, the review provided a critical discussion on the overall topic, identified all research gaps present in the use of NFRC for AM processes, and to overcome future challenges. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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30 pages, 1489 KiB  
Review
Review of Hybrid Fiber Based Composites with Nano Particles—Material Properties and Applications
by Ayyappa Atmakuri, Arvydas Palevicius, Andrius Vilkauskas and Giedrius Janusas
Polymers 2020, 12(9), 2088; https://doi.org/10.3390/polym12092088 - 14 Sep 2020
Cited by 46 | Viewed by 6347
Abstract
The present review article provides an overview of the properties of various natural and synthetic fibers for the fabrication of pure natural composites and the combination of both natural/synthetic fibers-based hybrid composites, bio-based resins, various fabrication techniques, chemical and mechanical properties of fibers, [...] Read more.
The present review article provides an overview of the properties of various natural and synthetic fibers for the fabrication of pure natural composites and the combination of both natural/synthetic fibers-based hybrid composites, bio-based resins, various fabrication techniques, chemical and mechanical properties of fibers, the effect of chemical treatment and the influence of nanoparticles on the composite materials. Natural fibers are becoming more popular and attractive to researchers, with satisfactory results, due to their availability, ease of fabrication, cost-effectiveness, biodegradable nature and being environmentally friendly. Hybrid composites made up of two different natural fibers under the same matrix material are more popular than a combination of natural and synthetic fibers. Recent studies relevant to natural fiber hybrid composites have stated that, due to their biodegradability and the strength of individual fibers causing an impact on mechanical properties, flame retardancy and moisture absorption, natural fibers need an additional treatment like chemical treatment for the fibers to overcome those drawbacks and to enhance their better properties. The result of chemical treatment on composite material properties such as thermal, mechanical and moisture properties was studied. Researchers found that the positive influence on overall strength by placing the filler materials (nanoparticles) in the composite materials. Hybrid composites are one of the fields in polymer science that are attracting consideration for various lightweight applications in a wide range of industries such as automobile, construction, shipping, aviation, sports equipment, electronics, hardware and biomedical sectors. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites II)
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