The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Romildo Dias Toledo Filho - One of the best experts on this subject based on the ideXlab platform.
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influence of water amount and immersion time on the sisal fibers Hornification process
Journal of Natural Fibers, 2019Co-Authors: Sophia Mendes, Romildo Dias Toledo Filho, Lisiane Nunes Hugen, Renata Daniel Santos, Saulo Rocha FerreiraAbstract:Hornification is phenomenon that can be promoted by wetting and drying treatment, which modify the microstructure of the lignocellulosic fibers, by promoting the stiffening of the polymeric structu...
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effect of Hornification on the structure tensile behavior and fiber matrix bond of sisal jute and curaua fiber cement based composite systems
Construction and Building Materials, 2017Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Abstract Several fiber treatments are used to mitigate the high water absorption of vegetable fibers. Wetting and drying cycles are usually performed in the industry of paper and cellulose to reduce the volume variation of these fibers. This procedure stiffens the polymeric structure of the fiber-cells (this process is known as Hornification) resulting in a higher dimensional stability. The aim of this study is to determine the effect of the Hornification on the chemical and mechanical behavior of natural fibers and how these properties influence the fiber matrix bond. For this purpose, 5 and 10 cycles of wet and drying were applied to curaua, jute and sisal fibers. Fiber pull-out tests were performed in the embedment length of 25 mm. Direct tensile tests were performed in natural and hornified fibers. Furthermore, X-ray diffraction, thermogravimetry analysis, infra red spectroscopy and nuclear magnetic resonance were used to investigate the influence of the Hornification on the chemical properties of the studied fibers. Modifications on the fiber morphology were observed with a scanning electron microscope. The results indicate changes on the tensile strength and strain capacity of the studied fibers, showing that morphology, physical aspects and chemical composition play an important role on the efficiency rate of Hornification. Significant improvement in the fiber-matrix interface was observed through the pullout tests. It was concluded that 5 cycles promotes a better performance to curaua and sisal fibers. Only the sisal fibers show improvement on its bond mechanisms after 10 cycles.
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Effect of fiber treatments on the sisal fiber properties and fiber–matrix bond in cement based systems
Construction and Building Materials, 2015Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Abstract This experimental research investigation aims to explain the influence of several treatments on the sisal fiber properties and bonding strength with a cement based matrix free of calcium hydroxide. Four different treatments were studied: Hornification, alkali treatment with calcium hydroxide, polymer impregnation with styrene butadiene and a combination of Hornification and polymer impregnation. Modifications in the sisal fiber structure were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM). Water absorption and direct tensile tests were performed on the fibers to determine the influence of the treatments on their physical and mechanical properties. In order to study the sisal fiber–matrix bond, pullout tests were performed in fiber embedment lengths of 5, 10, 25 and 50 mm. All applied treatments resulted in a reduction of the water absorption capacity and increase in tensile strength and stiffness. Significant improvements in the fiber–matrix interface were verified through the pullout test for the several used treatments. The Hornification treatment increased the elastic and frictional bond, whereas the polymer and hybrid treatments resulted in a fiber slip-hardening behavior.
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effect of natural fiber Hornification on the fiber matrix interface in cement based composite systems
Key Engineering Materials, 2015Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Several fiber treatments can be applied to mitigate the high water absorption of vegetal fibers. Wetting and drying cycles are usually performed in the industry of paper and cellulose to reduce the volume variation of the natural fibers. This procedure stiffens the polymeric structure of the fiber-cells (process known as Hornification) resulting in a higher dimensional stability. The aim of this study is to determine the effect of the Hornification on the interface of natural fibers. For this purpose, cycles of wet and drying was applied on Sisal, Curaua and Jute fibers. Fiber pull-out tests were performed in embedment lengths of 25mm. Furthermore, the influence of the Hornification in the fibers mechanical (under tensile loading) and microstructural (surface modifications of the fiber and changes in the fiber-cell structure) behavior were investigated. The results indicate changes on the tensile strength and strain capacity of the studied fibers, showing that morphology and chemical composition play an important role on the efficiency rate of Hornification.
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effect of sisal fiber Hornification on the fiber matrix bonding characteristics and bending behavior of cement based composites
Key Engineering Materials, 2014Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Cycles of wetting and drying can change the microstructure of vegetable fibers through a mechanism known as Hornification, which modifies the polymeric structure of the fiber-cells resulting in a higher dimensional stability. In the present work the influence of Hornification on the sisal fiber-matrix bond adhesion as well as in the sisal fiber dimensional stability and mechanical behaviour under direct tension was evaluated. Furthermore, cementitious composites reinforced with randomly dispersed hornified sisal fibers were developed and characterized under bending loads. The results show that the tensile strength and strain at failure of the hornified sisal fibers were increased by about 5% and 39%, respectively, whereas the modulus of elasticity was reduced by 9%. The fibers also presented higher dimensional stability with the Hornification process. The fiber-matrix bonding was improved and the pull-out resistance of the fibers submitted to ten cycles of wetting and drying was increased by about 40% to 50%. The higher fiber-matrix bond strength contributed to an increase in the ductility and post-cracking behaviour of the composite. The fracture process was characterized by the formation of multiple cracks with the hornified sisal fibers presenting a higher ability to bridge and arrest the cracks.
Juliano Fiorelli - One of the best experts on this subject based on the ideXlab platform.
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Synergic effect of fiber and matrix treatments for vegetable fiber reinforced cement of improved performance
Construction and Building Materials, 2019Co-Authors: Julian Eduardo Mejia Ballesteros, Gonzalo Mármol, Rafael Filomeno, Loïc Rodier, Holmer Savastano, Juliano FiorelliAbstract:Abstract This paper assesses for the first time the effect of accelerated carbonation and Hornification treatments on fiber-cement composites, both combined and independently. In order to improve the mechanical performance and durability of the material, the influence of each treatment over matrix and fiber is analyzed along time. The results indicate that Hornification treatment yields greater dimensional stability improving the fiber-matrix interface and greater Specific Energy of the composites, while accelerated carbonation generates denser matrices, which increases Modulus of Rupture. After accelerated aging, the combined effect of both treatments improved the mechanical performance compared to the rest of the samples. In addition, cellulose material is preserved, showing the potential efficiency of both treatments combined on fiber/matrix.
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Potential of the Hornification treatment on eucalyptus and pine fibers for fiber-cement applications
Cellulose, 2017Co-Authors: Julian Eduardo Mejia Ballesteros, Valdemir Santos, Gonzalo Mármol, Moisés Frías, Juliano FiorelliAbstract:In the industry of cement-based products, various lignocellulosic materials are used as reinforcing elements. These cellulosic materials are presented as potential alternatives because of their sustainability, low cost and technical features. However, plant fibers, in spite of good mechanical performance as reinforcement materials, exhibit a number of shortcomings in relation to durability in the alkaline environment of cementitious materials as well as dimensional variation due to their characteristic hygroscopic behavior. Thus, Hornification emerges as an alternative, economic and simple pretreatment that is expected to minimize these problems. This study evaluated the physical, chemical and morphological effects of four Hornification cycles on pine pulp and innovative eucalyptus pulps, both bleached and unbleached, proving that the treatment does not deteriorate the characteristics of interest of the fibers. Hornification modifies fiber surfaces and reduces their water absorption capacity, turning the pulps into more suitable materials and giving them the technical capability to reinforce brittle inorganic matrices.
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evaluation of cellulosic pulps treated by Hornification as reinforcement of cementitious composites
Construction and Building Materials, 2015Co-Authors: Julian Eduardo Mejia Ballesteros, Gonzalo Mármol, Holmer Savastano, S F Santos, Juliano FiorelliAbstract:Abstract This study evaluated the effect of the Hornification process on cellulosic fibers of bleached pine and unbleached eucalyptus with in order to improve its durability and volume stability to be used as reinforcement in cementitious matrices. The study indicated that the treatment did not deteriorate the properties of viscosity and index of crystallinity and decreased the capacity of water retention. Composites reinforced with hornificated and untreated pulps with thermal curing or accelerated aging were produced and evaluated to assess their physical and mechanical behavior. The use of hornificated fibers as reinforcement generated improvements in the modulus of rupture and specific energy of the composites.
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Evaluation of the Effect of Drying and Rewetting Cycles in Eucalyptus Pulps
International journal of engineering and technology, 2015Co-Authors: Julian E. Mejia B, Juliano Fiorelli, Holmer Savastano, Lisa VidilAbstract:In the fibrocement industry of tiles and sheets, various kinds of natural fibers are used as reinforcement to improve the properties of the products. Although the use of fibrocement material presents a great potential due to the low cost and the high availability of vegetable fibers, several investigations have showed a behavior of low durability and rapid deterioration of the cellulosic material in an alkaline medium. With the purpose of contributing to this knowledge, the present study evaluated bleached and unbleached cellulosic pulp of eucalyptus before and after the thermal treatment consisting of 4 cycles of drying and rewetting denominated Hornification. Analysis by scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed. SEM images indicated morphological changes on the surface of treated bleached and unbleached eucalyptus cellulosic pulps. Based on XRDresults, the treatment Hornification did not cause the deterioration of crystalline cellulose of the fibers.
Tekla Tammelin - One of the best experts on this subject based on the ideXlab platform.
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prevention of interfibril Hornification by replacing water in nanocellulose gel with low molecular weight liquid poly ethylene glycol
Carbohydrate Polymers, 2020Co-Authors: Alba Santmarti, Tekla TammelinAbstract:Abstract Nanocellulose is typically stored and transported as a gel with a nominal solid content of up to 5 wt.-% to avoid interfibril Hornification, i.e. the formation of irreversible hydrogen bonds between adjacent nanocellulose upon drying, which makes nanocellulose not cost-effective. In this work, we report the use of low molecular weight liquid poly(ethylene glycol) (PEG-200) as a replacement for the water phase in nanocellulose aqueous gel. Our results indicated that nanocellulose can be stored in PEG-200 at a solid content of up to 70 wt.-% without interfibril Hornification, even when exposed to the ambient environment. This is due to the low vapour pressure and high boiling point of PEG-200. ATR-FTIR and ζ-potential measurements confirmed that PEG-200 can be easily washed out from the nanocellulose as PEG-200 is water miscible. Using PEG-200 as a replacement for the water phase in nanocellulose aqueous gel could improve the cost-efficiency of nanocellulose storage and transportation. The tensile properties of the cellulose nanopaper prepared from the various never-dried and once-dried nanocellulose are also discussed in this work.
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Prevention of interfibril Hornification by replacing water in nanocellulose gel with low molecular weight liquid poly(ethylene glycol)
Carbohydrate Polymers, 2020Co-Authors: Alba Santmarti, Tekla TammelinAbstract:Abstract Nanocellulose is typically stored and transported as a gel, with a nominal solid content of up to ∼5 wt.-% to avoid interfibril Hornification, i.e. the formation of irreversible hydrogen bonds between adjacent nanocellulose upon drying, which makes nanocellulose not cost-effective. In this work, we report the use of low molecular weight liquid poly(ethylene glycol) (PEG-200) as a replacement for the water phase in nanocellulose aqueous gel. Our results indicated that nanocellulose can be stored in PEG-200 at a solid content of up to 70 wt.-% without interfibril Hornification, even when exposed to the ambient environment. This is due to the low vapour pressure and high boiling point of PEG-200. ATR-FTIR and ζ-potential measurements confirmed that PEG-200 can be easily washed out from the nanocellulose as PEG-200 is water miscible. Using PEG-200 as a replacement for the water phase in nanocellulose aqueous gel could improve the cost-efficiency of nanocellulose storage and transportation. The tensile properties of the cellulose nanopaper prepared from the various never-dried nanocellulose and once-dried nanocellulose are also discussed in this work.
Saulo Rocha Ferreira - One of the best experts on this subject based on the ideXlab platform.
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influence of water amount and immersion time on the sisal fibers Hornification process
Journal of Natural Fibers, 2019Co-Authors: Sophia Mendes, Romildo Dias Toledo Filho, Lisiane Nunes Hugen, Renata Daniel Santos, Saulo Rocha FerreiraAbstract:Hornification is phenomenon that can be promoted by wetting and drying treatment, which modify the microstructure of the lignocellulosic fibers, by promoting the stiffening of the polymeric structu...
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effect of Hornification on the structure tensile behavior and fiber matrix bond of sisal jute and curaua fiber cement based composite systems
Construction and Building Materials, 2017Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Abstract Several fiber treatments are used to mitigate the high water absorption of vegetable fibers. Wetting and drying cycles are usually performed in the industry of paper and cellulose to reduce the volume variation of these fibers. This procedure stiffens the polymeric structure of the fiber-cells (this process is known as Hornification) resulting in a higher dimensional stability. The aim of this study is to determine the effect of the Hornification on the chemical and mechanical behavior of natural fibers and how these properties influence the fiber matrix bond. For this purpose, 5 and 10 cycles of wet and drying were applied to curaua, jute and sisal fibers. Fiber pull-out tests were performed in the embedment length of 25 mm. Direct tensile tests were performed in natural and hornified fibers. Furthermore, X-ray diffraction, thermogravimetry analysis, infra red spectroscopy and nuclear magnetic resonance were used to investigate the influence of the Hornification on the chemical properties of the studied fibers. Modifications on the fiber morphology were observed with a scanning electron microscope. The results indicate changes on the tensile strength and strain capacity of the studied fibers, showing that morphology, physical aspects and chemical composition play an important role on the efficiency rate of Hornification. Significant improvement in the fiber-matrix interface was observed through the pullout tests. It was concluded that 5 cycles promotes a better performance to curaua and sisal fibers. Only the sisal fibers show improvement on its bond mechanisms after 10 cycles.
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Effect of fiber treatments on the sisal fiber properties and fiber–matrix bond in cement based systems
Construction and Building Materials, 2015Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Abstract This experimental research investigation aims to explain the influence of several treatments on the sisal fiber properties and bonding strength with a cement based matrix free of calcium hydroxide. Four different treatments were studied: Hornification, alkali treatment with calcium hydroxide, polymer impregnation with styrene butadiene and a combination of Hornification and polymer impregnation. Modifications in the sisal fiber structure were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM). Water absorption and direct tensile tests were performed on the fibers to determine the influence of the treatments on their physical and mechanical properties. In order to study the sisal fiber–matrix bond, pullout tests were performed in fiber embedment lengths of 5, 10, 25 and 50 mm. All applied treatments resulted in a reduction of the water absorption capacity and increase in tensile strength and stiffness. Significant improvements in the fiber–matrix interface were verified through the pullout test for the several used treatments. The Hornification treatment increased the elastic and frictional bond, whereas the polymer and hybrid treatments resulted in a fiber slip-hardening behavior.
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effect of natural fiber Hornification on the fiber matrix interface in cement based composite systems
Key Engineering Materials, 2015Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Several fiber treatments can be applied to mitigate the high water absorption of vegetal fibers. Wetting and drying cycles are usually performed in the industry of paper and cellulose to reduce the volume variation of the natural fibers. This procedure stiffens the polymeric structure of the fiber-cells (process known as Hornification) resulting in a higher dimensional stability. The aim of this study is to determine the effect of the Hornification on the interface of natural fibers. For this purpose, cycles of wet and drying was applied on Sisal, Curaua and Jute fibers. Fiber pull-out tests were performed in embedment lengths of 25mm. Furthermore, the influence of the Hornification in the fibers mechanical (under tensile loading) and microstructural (surface modifications of the fiber and changes in the fiber-cell structure) behavior were investigated. The results indicate changes on the tensile strength and strain capacity of the studied fibers, showing that morphology and chemical composition play an important role on the efficiency rate of Hornification.
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effect of sisal fiber Hornification on the fiber matrix bonding characteristics and bending behavior of cement based composites
Key Engineering Materials, 2014Co-Authors: Saulo Rocha Ferreira, Flavio De Andrade Silva, Paulo Roberto Lopes Lima, Romildo Dias Toledo FilhoAbstract:Cycles of wetting and drying can change the microstructure of vegetable fibers through a mechanism known as Hornification, which modifies the polymeric structure of the fiber-cells resulting in a higher dimensional stability. In the present work the influence of Hornification on the sisal fiber-matrix bond adhesion as well as in the sisal fiber dimensional stability and mechanical behaviour under direct tension was evaluated. Furthermore, cementitious composites reinforced with randomly dispersed hornified sisal fibers were developed and characterized under bending loads. The results show that the tensile strength and strain at failure of the hornified sisal fibers were increased by about 5% and 39%, respectively, whereas the modulus of elasticity was reduced by 9%. The fibers also presented higher dimensional stability with the Hornification process. The fiber-matrix bonding was improved and the pull-out resistance of the fibers submitted to ten cycles of wetting and drying was increased by about 40% to 50%. The higher fiber-matrix bond strength contributed to an increase in the ductility and post-cracking behaviour of the composite. The fracture process was characterized by the formation of multiple cracks with the hornified sisal fibers presenting a higher ability to bridge and arrest the cracks.
Julian Eduardo Mejia Ballesteros - One of the best experts on this subject based on the ideXlab platform.
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Synergic effect of fiber and matrix treatments for vegetable fiber reinforced cement of improved performance
Construction and Building Materials, 2019Co-Authors: Julian Eduardo Mejia Ballesteros, Gonzalo Mármol, Rafael Filomeno, Loïc Rodier, Holmer Savastano, Juliano FiorelliAbstract:Abstract This paper assesses for the first time the effect of accelerated carbonation and Hornification treatments on fiber-cement composites, both combined and independently. In order to improve the mechanical performance and durability of the material, the influence of each treatment over matrix and fiber is analyzed along time. The results indicate that Hornification treatment yields greater dimensional stability improving the fiber-matrix interface and greater Specific Energy of the composites, while accelerated carbonation generates denser matrices, which increases Modulus of Rupture. After accelerated aging, the combined effect of both treatments improved the mechanical performance compared to the rest of the samples. In addition, cellulose material is preserved, showing the potential efficiency of both treatments combined on fiber/matrix.
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Potential of the Hornification treatment on eucalyptus and pine fibers for fiber-cement applications
Cellulose, 2017Co-Authors: Julian Eduardo Mejia Ballesteros, Valdemir Santos, Gonzalo Mármol, Moisés Frías, Juliano FiorelliAbstract:In the industry of cement-based products, various lignocellulosic materials are used as reinforcing elements. These cellulosic materials are presented as potential alternatives because of their sustainability, low cost and technical features. However, plant fibers, in spite of good mechanical performance as reinforcement materials, exhibit a number of shortcomings in relation to durability in the alkaline environment of cementitious materials as well as dimensional variation due to their characteristic hygroscopic behavior. Thus, Hornification emerges as an alternative, economic and simple pretreatment that is expected to minimize these problems. This study evaluated the physical, chemical and morphological effects of four Hornification cycles on pine pulp and innovative eucalyptus pulps, both bleached and unbleached, proving that the treatment does not deteriorate the characteristics of interest of the fibers. Hornification modifies fiber surfaces and reduces their water absorption capacity, turning the pulps into more suitable materials and giving them the technical capability to reinforce brittle inorganic matrices.
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evaluation of cellulosic pulps treated by Hornification as reinforcement of cementitious composites
Construction and Building Materials, 2015Co-Authors: Julian Eduardo Mejia Ballesteros, Gonzalo Mármol, Holmer Savastano, S F Santos, Juliano FiorelliAbstract:Abstract This study evaluated the effect of the Hornification process on cellulosic fibers of bleached pine and unbleached eucalyptus with in order to improve its durability and volume stability to be used as reinforcement in cementitious matrices. The study indicated that the treatment did not deteriorate the properties of viscosity and index of crystallinity and decreased the capacity of water retention. Composites reinforced with hornificated and untreated pulps with thermal curing or accelerated aging were produced and evaluated to assess their physical and mechanical behavior. The use of hornificated fibers as reinforcement generated improvements in the modulus of rupture and specific energy of the composites.