Fibers

12 pages, 3178 KiB

Open AccessEditor’s ChoiceArticle

Production of Nanocellulose from Pineapple Leaf Fibers via High-Shear Homogenization and Ultrasonication

by Melbi Mahardika, Hairul Abral, Anwar Kasim, Syukri Arief and Mochamad Asrofi

Fibers 2018, 6(2), 28; https://doi.org/10.3390/fib6020028 - 3 May 2018

Cited by 163 | Viewed by 16613

In this study, the isolation and characterization of nanocellulose from pineapple leaf fibers (PLF) were carried out. Chemical pretreatment included pulping, bleaching, and acid hydrolysis to remove lignin, hemicellulose, and extractive substances were conducted. This was followed by high-shear homogenization and ultrasonication to [...] Read more.

In this study, the isolation and characterization of nanocellulose from pineapple leaf fibers (PLF) were carried out. Chemical pretreatment included pulping, bleaching, and acid hydrolysis to remove lignin, hemicellulose, and extractive substances were conducted. This was followed by high-shear homogenization and ultrasonication to produce nanocellulose. Morphological changes to the PLF due to treatment were investigated using scanning electron microscopy (SEM). This showed that the PLF had a diameter of 1–10 µm after high-shear homogenizing. Transmission electron microscopy (TEM) indicated that the nanofibers after ultrasonication for 60 min showed 40–70 nm diameters. Particle size analysis (PSA) indicates that the fibers had an average diameter of 68 nm. Crystallinity index was determined by X-ray diffraction (XRD) and had the highest value after acid hydrolysis at 83% but after 60 min ultrasonication, this decreased to 62%. Meanwhile, Fourier transform infrared (FTIR) spectroscopy showed there was no chemical structure change after acid hydrolysis. The most significant finding from thermal gravimetric analysis (TGA) is that the higher degradation temperature of nanofibers indicates superior thermal stability over untreated fiber. These results indicate that PLF waste could become a viable source of commercially valuable nanocellulose. Full article

(This article belongs to the Special Issue Biopolymer Nanofiber)

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8 pages, 3287 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Shatter-Proof Metal Hollow-Core Optical Fibers for Endoscopic Mid-Infrared Laser Applications

by Katsumasa Iwai, Hiroyuki Takaku, Mitsunobu Miyagi, Yi-Wei Shi and Yuji Matsuura

Fibers 2018, 6(2), 24; https://doi.org/10.3390/fib6020024 - 18 Apr 2018

Cited by 11 | Viewed by 6739

Abstract

A method for fabricating robust and thin hollow-core optical fibers that carry mid-infrared light is proposed for use in endoscopic laser applications. The fiber is made of stainless steel tubing, eliminating the risk of scattering small glass fragments inside the body if the [...] Read more.

A method for fabricating robust and thin hollow-core optical fibers that carry mid-infrared light is proposed for use in endoscopic laser applications. The fiber is made of stainless steel tubing, eliminating the risk of scattering small glass fragments inside the body if the fiber breaks. To reduce the inner surface roughness of the tubing, a polymer base layer is formed prior to depositing silver and optical-polymer layers that confine light inside the hollow core. The surface roughness is greatly decreased by re-coating thin polymer base layers. Because of this smooth base layer surface, a uniform optical-polymer film can be formed around the core. As a result, clear interference peaks are observed in both the visible and mid-infrared regions. Transmission losses were also low for the carbon dioxide laser used for medical treatments as well as the visible laser diode used for an aiming beam. Measurements of bending losses for these lasers demonstrate the feasibility of the designed fiber for endoscopic applications. Full article

(This article belongs to the Special Issue Hollow Core Optical Fibers)

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11 pages, 18662 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Key Stages of Fiber Development as Determinants of Bast Fiber Yield and Quality

by Natalia Mokshina, Tatyana Chernova, Dmitry Galinousky, Oleg Gorshkov and Tatyana Gorshkova

Fibers 2018, 6(2), 20; https://doi.org/10.3390/fib6020020 - 2 Apr 2018

Cited by 27 | Viewed by 12657

Abstract

Plant fibers find wide application in various fields that demand specific parameters of fiber quality. To develop approaches for the improvement of yield and quality of bast fibers, the knowledge of the fiber developmental stages and of the key molecular players that are [...] Read more.

Plant fibers find wide application in various fields that demand specific parameters of fiber quality. To develop approaches for the improvement of yield and quality of bast fibers, the knowledge of the fiber developmental stages and of the key molecular players that are responsible for a certain parameter, are vitally important. In the present review the key stages of fiber development, such as initiation, intrusive growth, and formation of thickened cell wall layers (secondary and tertiary cell walls) are considered, as well as the impact of each of these stages on the final parameters of fiber yield and quality. The problems and perspectives of crop quality regulation are discussed. Full article

(This article belongs to the Special Issue Plant Bast Fibers)

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19 pages, 11998 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Synthetic Strategies for the Fabrication of Cationic Surface-Modified Cellulose Nanocrystals

by Rajesh Sunasee and Usha D. Hemraz

Fibers 2018, 6(1), 15; https://doi.org/10.3390/fib6010015 - 5 Mar 2018

Cited by 38 | Viewed by 12616

Abstract

Cellulose nanocrystals (CNCs) are renewable nanosized materials with exceptional physicochemical properties that continue to garner a high level of attention in both industry and academia for their potential high-end material applications. These rod-shaped CNCs are appealing due to their non-toxic, carbohydrate-based chemical structure, [...] Read more.

Cellulose nanocrystals (CNCs) are renewable nanosized materials with exceptional physicochemical properties that continue to garner a high level of attention in both industry and academia for their potential high-end material applications. These rod-shaped CNCs are appealing due to their non-toxic, carbohydrate-based chemical structure, large surface area, and the presence of ample surface hydroxyl groups for chemical surface modifications. CNCs, generally prepared from sulfuric acid-mediated hydrolysis of native cellulose, display an anionic surface that has been exploited for a number of applications. However, several recent studies showed the importance of CNCs’ surface charge reversal towards the design of functional cationic CNCs. Cationization of CNCs could further open up other innovative applications, in particular, bioapplications such as gene and drug delivery, vaccine adjuvants, and tissue engineering. This mini-review focuses mainly on the recent covalent synthetic methods for the design and fabrication of cationic CNCs as well as their potential bioapplications. Full article

(This article belongs to the Special Issue Current Developments in Cellulose Based Nanomaterials)

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13 pages, 7356 KiB

Open AccessEditor’s ChoiceReview

Advances on Polymer Optical Fiber Gratings Using a KrF Pulsed Laser System Operating at 248 nm

by Carlos A. F. Marques, Arnaldo G. Leal-Junior, Rui Min, Maria Domingues, Cátia Leitão, Paulo Antunes, Beatriz Ortega and Paulo André

Fibers 2018, 6(1), 13; https://doi.org/10.3390/fib6010013 - 1 Mar 2018

Cited by 68 | Viewed by 6576

Abstract

This paper presents the achievements and progress made on the polymer optical fiber (POF) gratings inscription in different types of Fiber Bragg Gratings (FBGs) and long period gratings (LPGs). Since the first demonstration of POFBGs in 1999, significant progress has been made where [...] Read more.

This paper presents the achievements and progress made on the polymer optical fiber (POF) gratings inscription in different types of Fiber Bragg Gratings (FBGs) and long period gratings (LPGs). Since the first demonstration of POFBGs in 1999, significant progress has been made where the inscription times that were higher than 1 h have been reduced to 15 ns with the application of the krypton fluoride (KrF) pulsed laser operating at 248 nm and thermal treatments such as the pre-annealing of fibers. In addition, the application of dopants such as benzyl dimethyl ketal (BDK) has provided a significant decrease of the fiber inscription time. Furthermore, such improvements lead to the possibility of inscribing POF gratings in 850 nm and 600 nm, instead of only the 1550 nm region. The progress on the inscription of different types of polymer optical fiber Bragg gratings (POFBGs) such as chirped POFBGs and phase-shifted POFBGs are also reported in this review. Full article

(This article belongs to the Special Issue Optical Fiber Communications)

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13 pages, 7458 KiB

Open AccessEditor’s ChoiceArticle

Restrained Shrinkage Cracking of Fiber-Reinforced High-Strength Concrete

by Ashkan Saradar, Behzad Tahmouresi, Ehsan Mohseni and Ali Shadmani

Fibers 2018, 6(1), 12; https://doi.org/10.3390/fib6010012 - 19 Feb 2018

Cited by 76 | Viewed by 10539

Abstract

Concrete shrinkage and volume reduction happens due to the loss of moisture, which eventually results in cracks and more concrete deformation. In this study, the effect of polypropylene (PP), steel, glass, basalt, and polyolefin fibers on compressive and flexural strength, drying shrinkage, and [...] Read more.

Concrete shrinkage and volume reduction happens due to the loss of moisture, which eventually results in cracks and more concrete deformation. In this study, the effect of polypropylene (PP), steel, glass, basalt, and polyolefin fibers on compressive and flexural strength, drying shrinkage, and cracking potential, using the ring test at early ages of high-strength concrete mixtures, was investigated. The restrained shrinkage test was performed on concrete ring specimens according to the ASTM C1581 standard. The crack width and age of restrained shrinkage cracking were the main parameters studied in this research. The results indicated that the addition of fiber increases the compressive strength by 16%, 20%, and 3% at the age of 3, 7, and 28 days, respectively, and increases the flexural toughness index up to 7.7 times. Steel and glass fibers had a better performance in flexural strength, but relatively poor action in the velocity reduction and cracking time of the restrained shrinkage. Additionally, cracks in all concrete ring specimens except for the polypropylene-containing mixture, was developed to a full depth crack. The mixture with polypropylene fiber indicated a reduction in crack width up to 62% and an increasing age cracking up to 84%. Full article

(This article belongs to the Special Issue Recent Advancements in Fiber Reinforced Concrete And its Applications)

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9 pages, 2113 KiB

Open AccessFeature PaperEditor’s ChoiceCommunication

Investigation of the Mechanical Properties of Flax Cell Walls during Plant Development: The Relation between Performance and Cell Wall Structure

by Camille Goudenhooft, David Siniscalco, Olivier Arnould, Alain Bourmaud, Olivier Sire, Tatyana Gorshkova and Christophe Baley

Fibers 2018, 6(1), 6; https://doi.org/10.3390/fib6010006 - 17 Jan 2018

Cited by 47 | Viewed by 8150

Abstract

The development of flax (Linum usitatissimum L.) fibers was studied to obtain better insight on the progression of their high mechanical performances during plant growth. Fibers at two steps of plant development were studied, namely the end of the fast growth period [...] Read more.

The development of flax (Linum usitatissimum L.) fibers was studied to obtain better insight on the progression of their high mechanical performances during plant growth. Fibers at two steps of plant development were studied, namely the end of the fast growth period and at plant maturity, each time at three plant heights. The indentation modulus of the fiber cell wall was characterized by atomic force microscopy (AFM) using peak-force quantitative nano-mechanical property mapping (PF-QNM). Changes in the cell wall modulus with the cell wall thickening were highlighted. For growing plants, fibers from top and middle heights show a loose inner Gn layer with a lower indentation modulus than mature fibers, which exhibit thickened homogeneous cell walls made only of a G layer. The influence of these changes in the fiber cell wall on the mechanical performances of extracted elementary fibers was also emphasized by tensile tests. In addition, Raman spectra were recorded on samples from both growing and mature plants. The results suggest that, for the fiber cell wall, the cellulose contribution increases with fiber maturity, leading to a greater cell wall modulus of flax fibers. Full article

(This article belongs to the Special Issue Plant Bast Fibers)

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10 pages, 2949 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Filler Orientation on the Electrical Conductivity of Carbon Fiber/PMMA Composites

by Muchao Qu, Fritjof Nilsson and Dirk W. Schubert

Fibers 2018, 6(1), 3; https://doi.org/10.3390/fib6010003 - 1 Jan 2018

Cited by 40 | Viewed by 9719

Abstract

The electrical conductivity of extruded carbon fiber (CF)/Polymethylmethacrylate (PMMA) composites with controlled CF aspect ratio and filler fractions ranging from 0 to 50 vol. % has been investigated and analyzed. The composites were extruded through a capillary rheometer, utilizing either 1-mm or 3-mm [...] Read more.

The electrical conductivity of extruded carbon fiber (CF)/Polymethylmethacrylate (PMMA) composites with controlled CF aspect ratio and filler fractions ranging from 0 to 50 vol. % has been investigated and analyzed. The composites were extruded through a capillary rheometer, utilizing either 1-mm or 3-mm diameter extrusion dies, resulting in cylindrical composite filaments of two different diameters. Since the average CF orientation becomes more aligned with the extrusion flow when the diameter of the extrusion dies decreases, the relationship between conductivity and average fiber orientation could therefore be examined. The room temperature conductivities of the extruded filaments as a function of CF fractions were fitted to the McLachlan general effective medium (GEM) equation and the percolation thresholds were determined to 20.0 ± 2.5 vol. % and 32.0 ± 5.9 vol. % for the 3-mm (with CFs oriented less) and 1-mm (with CFs oriented more) filaments, respectively. It turned out that the oriented CFs in the composite shift the percolation threshold to a higher value, however, the conductivity above the percolation threshold is higher for composites with oriented CFs. A novel approach based on the Balberg excluded volume theory was proposed to explain this counterintuitive phenomenon. Full article

(This article belongs to the Special Issue Carbon Fiber Reinforced Composites)

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