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Elisabete Frollini - One of the best experts on this subject based on the ideXlab platform.
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tannin phenolic resins synthesis characterization and application as matrix in biobased composites reinforced with Sisal fibers
Composites Part B-engineering, 2012Co-Authors: Elaine C Ramires, Elisabete FrolliniAbstract:Abstract A tannin–phenolic resin (40 wt% of tannin, characterized by 1 H nuclear magnetic resonance (NMR) and 13 C NMR, Fourier transform infrared, thermogravimetry, differential scanning calorimetry) was used to prepare composites reinforced with Sisal fibers (30–70 wt%). Inverse gas chromatography results showed that the Sisal fibers and the tannin–phenolic thermoset have close values of the dispersive component and also have predominance of acid sites (acid character) at the surface, confirming the favoring of interaction between the Sisal fibers and the tannin–phenolic matrix at the interface. The Izod impact strength increased up to 50 wt% of Sisal fibers. This composite also showed high storage modulus, and the lower loss modulus, confirming its good fiber/matrix interface, also observed by SEM images. A composite with good properties was prepared from high content of raw material obtained from renewable sources (40 wt% of tannin substituted the phenol in the preparation of the matrix and 50 wt% of matrix was replaced by Sisal fibers).
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Some aspects of acetylation of untreated and mercerized Sisal cellulose
Journal of the Brazilian Chemical Society, 2010Co-Authors: Gabriela T. Ciacco, Elisabete Frollini, Daniella Lury Morgado, Shirley Possidonio, Omar A. El SeoudAbstract:We report here on some aspects of the acetylation in LiCl/N,N-dimethylacetamide, DMAc, of untreated and mercerized Sisal cellulose, hereafter designated as Sisal and M-Sisal, respectively. Fiber mercerization by NaOH solution has resulted in the following changes: 29.9% decrease in the index of crystallinity; 16.2% decrease in the degree of polymerization and 9.3% increase in α-cellulose content. A light scattering study of solutions of Sisal, M-Sisal, microcrystalline and cotton celluloses in LiCl/DMAc has shown that they are present as aggregates, with (an apparent) average aggregation numbers of 5.2, 3.2, 9.8, and 35.3, respectively. The presence of these aggregates affects the accessibility of cellulose during its functionalization. A study of the evolution of the degree of substitution, DS, of cellulose acetate as a function of reaction time showed an increase up to 5 h, followed by a decrease at 7 h. Possible reasons for this decrease are discussed. As expected, M-Sisal gave a higher DS that its untreated counterpart.
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Sisal cellulose acetates obtained from heterogeneous reactions
Express Polymer Letters, 2008Co-Authors: M. Peres De Paula, Talita M. Lacerda, Elisabete FrolliniAbstract:In the present work, cellulose obtained from Sisal, which is a source of rapid growth, was used. Cellulose acetates were produced in heterogeneous medium, using acetic anhydride as esterifying agent and iodine as catalyst, to check if the procedure described in the literature for commercial cellulose also is adequate to Sisal cellulose. The results indicated that iodine is an excellent catalyst to obtain Sisal cellulose acetates, but the reaction is so fast as described in the literature when, instead of Sisal, lower average molar weight cellulose (microcrystalline) is used. The crystallinity index (Ic) of Sisal cellulose acetates diminished compared to Sisal cellulose, but there was no direct correlation between their degree of substitution (DS) and Ic. Probably acetyl groups were introduced more homogeneously along the short chains of microcrystalline cellulose, when compared to Sisal cellulose, and then for microcrystalline cellulose acetates the Ic decreases as DS increases. Using the linear correlation that was found between degree of substitution (DS) and time reaction is possible to control the DS of Sisal cellulose acetates, considering a large interval of degrees of substitution (0.3–2.8).
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unmodified and modified surface Sisal fibers as reinforcement of phenolic and lignophenolic matrices composites thermal analyses of fibers and composites
Macromolecular Materials and Engineering, 2006Co-Authors: Jane M F Paiva, Elisabete FrolliniAbstract:The study and development of polymeric composite materials, especially using lignocellulosic fibers, have received increasing attention. This is interesting from the environmental and economical viewpoints as lignocellulosic fibers are obtained from renewable resources. This work aims to contribute to reduce the dependency on materials from nonrenwable sources, by utilizing natural fibers (Sisal) as reinforcing agents and lignin (a polyphenolic macromolecule obtained from lignocellulosic materials) to partially substitute phenol in a phenol-formaldehyde resin. Besides, it was intented to evaluate how modifications applied on Sisal fibers influence their properties and those of the composites reinforced with tem, mainly thermal properties. Sisal fibers were modified by either (i) mercerization (NaOh 10%), (ii) esterification (succinic anhydride), or (iii) ionized air treatment (discharge current of 5 mA). Composites were made by mould compression, of various Sisal fibers in combination with either phenol-formaldehyde or lignin-phenol-formaldehyde resins. Sisal fibers and composites were characterized by thermogravimetry (TG) and DSC to establish their thermal stability. Scanning electron microscopy (SEM) was used to investigate the morphology of unmodified and modified surface Sisal fibers as well as the fractured composites surface. Dynamic mechnical thermoanalysis (DMTA) was used to examine the influence of temperature on the composite mechanical properties. The results obtained for Sisal fiber-reinforced phenolic and lignophenolic composites showed that the use of lignin as a partial substitute of phenol in phenolic resins in applications different from the traditional ones, as for instance in other than adhesives is feasible.
Nantaya Yanumet - One of the best experts on this subject based on the ideXlab platform.
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Mechanical property improvement of unsaturated polyester composite reinforced with admicellar-treated Sisal fibers
Composites Part A: Applied Science and Manufacturing, 2009Co-Authors: Supranee Sangthong, Thirawudh Pongprayoon, Nantaya YanumetAbstract:Sisal fiber was treated by admicellar polymerization with a poly(methyl methacrylate) film coating in order to enhance the interfacial adhesion of the fiber/polymer composite for mechanical property improvement. Properties of the admicellar-treated Sisal fiber were investigated by measuring its moisture absorption and electrostatic charge. Thermal stability study by thermogravimetric analysis and film identification by FTIR was also carried out. The treatment was shown to improve the tensile and flexural properties, impact strength, and hardness of the composite. SEM micrographs of the tensile fracture surface of Sisal/unsaturated polyester composites also show interfacial adhesion improvement of the composite prepared with admicellar-treated Sisal. © 2009.
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Surface Treatment of Sisal Fiber with Polymethylmethacrylate by Admicellar Polymerization
2006Co-Authors: Supranee Sangthong, Thirawudh Pongprayoon, Nantaya YanumetAbstract:Admicellar polymerization was applied to modify Sisal surface with polymethylmethacrylate (PMMA) to improve the compatibility of composite materials between natural fiber and polymeric matrix. This work studied the effects of varying amount of monomer (methylmethacrylate (MMA)) and initiator (sodium persulfate) on the hydrophobicity behavior of the surface of admicellar-treated Sisal. The increase in the hydrophobicity of the treated fiber surface was examined by the flotation test and electrostatic charge (or zeta potential) measurement. The PMMA film formed on Sisal fiber surface was identified by Fourier transforms infrared (FTIR). The results show that the thin film of PMMA was successfully formed on Sisal fiber to develop its surface to be hydrophobic surface that will enhance the compatibility of natural fiber composites. The admicellar-treated Sisal can float on water surface for longer than half an hour and the zeta potential of its surface also shows a significant change compared to the untreated Sisal. The results of both techniques showed that the amount of monomer and initiator had the effect on the hydrophobic characteristic of the treated Sisal surface.
Supranee Sangthong - One of the best experts on this subject based on the ideXlab platform.
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Mechanical property improvement of unsaturated polyester composite reinforced with admicellar-treated Sisal fibers
Composites Part A: Applied Science and Manufacturing, 2009Co-Authors: Supranee Sangthong, Thirawudh Pongprayoon, Nantaya YanumetAbstract:Sisal fiber was treated by admicellar polymerization with a poly(methyl methacrylate) film coating in order to enhance the interfacial adhesion of the fiber/polymer composite for mechanical property improvement. Properties of the admicellar-treated Sisal fiber were investigated by measuring its moisture absorption and electrostatic charge. Thermal stability study by thermogravimetric analysis and film identification by FTIR was also carried out. The treatment was shown to improve the tensile and flexural properties, impact strength, and hardness of the composite. SEM micrographs of the tensile fracture surface of Sisal/unsaturated polyester composites also show interfacial adhesion improvement of the composite prepared with admicellar-treated Sisal. © 2009.
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Surface Treatment of Sisal Fiber with Polymethylmethacrylate by Admicellar Polymerization
2006Co-Authors: Supranee Sangthong, Thirawudh Pongprayoon, Nantaya YanumetAbstract:Admicellar polymerization was applied to modify Sisal surface with polymethylmethacrylate (PMMA) to improve the compatibility of composite materials between natural fiber and polymeric matrix. This work studied the effects of varying amount of monomer (methylmethacrylate (MMA)) and initiator (sodium persulfate) on the hydrophobicity behavior of the surface of admicellar-treated Sisal. The increase in the hydrophobicity of the treated fiber surface was examined by the flotation test and electrostatic charge (or zeta potential) measurement. The PMMA film formed on Sisal fiber surface was identified by Fourier transforms infrared (FTIR). The results show that the thin film of PMMA was successfully formed on Sisal fiber to develop its surface to be hydrophobic surface that will enhance the compatibility of natural fiber composites. The admicellar-treated Sisal can float on water surface for longer than half an hour and the zeta potential of its surface also shows a significant change compared to the untreated Sisal. The results of both techniques showed that the amount of monomer and initiator had the effect on the hydrophobic characteristic of the treated Sisal surface.
Lei Tian - One of the best experts on this subject based on the ideXlab platform.
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Effect of Sisal Fiber Surface Treatments on Sisal Fiber Reinforced Polypropylene (PP) Composites
Advanced Materials Research, 2014Co-Authors: Hou Lei Gan, Lei TianAbstract:Abstract: The Interface of Sisal fiber which was treated by using alkali, potassium permanganate, atmospheric plasma and silane reinforced polypropylene composites were investigated by single fiber pull-out testes and surface morphology were studied. The results indicated that the morphological changes observed on the Sisal fiber surface were obviously evident. Untreated, permanganate and plasma treated Sisal fiber reinforced PP show a stable debonding process. Silane treated Sisal fiber reinforced PP show an unstable debonding process. Single fiber pull-out tests indicated that the IFSS value was in the order of FIB < FIBKMnO4 < FIBP < FIBKH-550 < FIBKH-570. As can be seen from surface morphology of pull-out fiber, a little of PP resin was adhered to the pull-out FIB, FIBKMnO4, FIBP of Sisal fiber. In contrast, PP resin at the surface of pull-out fiber was flaked off and Sisal fibril was drawn out from Sisal fiber were observed from pull-out fibers of FIBKH-550 and FIBKH-570.
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Crystalline transition behavior of Sisal in cycle process
Polymer Composites, 2009Co-Authors: Lei Tian, Fen Tang, Luoxin Wang, Hantao ZouAbstract:In this study, the effects of cycle process on crystalline transition behavior of Sisal fiber were investigated in various conditions (in air, in composites and in argon) by XRD analysis. The results indicated that the Sisal cellulose falls into cellulose I, and the polymorphic transformation didn't occur for Sisal cellulose after cycle process. With increasing of thermal cycle times, the crystalline size of Sisal became smaller gradually, but the change was not obvious when Sisal fiber was treated thermally in air and in argon before five times. The change trend of crystalline index of Sisal after cycle process in air and in argon was similar. However, it is different in composites. From once to 10 times cycle process, the crystalline index of Sisal fiber was degressive. When the cycle times was close to 15, crystalline index increased gradually. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
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Thermal stability and mechanical properties of Sisal in cycle process
Journal of Thermal Analysis and Calorimetry, 2008Co-Authors: Lei Tian, Y. TongAbstract:In this study, the thermal stability of Sisal in cycle process was investigated between room temperatures and 600°C in various conditions (in air, in composites, in argon) by thermogravimetry and mechanical testing measurement. The results indicated that the thermal stability of Sisal was worse in air before five times of thermal cycles, but after the five times thermal stability of Sisal in composites was better. In different conditions of same cycles process, the thermal stability of Sisal was different. With increasing of thermal cycles times, the max. load (is the maximum strength in stress-strain curve) of Sisal fiber showed downtendency in different conditions and decreased most obviously in composites.
A Valenza - One of the best experts on this subject based on the ideXlab platform.
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a new eco friendly chemical treatment of natural fibres effect of sodium bicarbonate on properties of Sisal fibre and its epoxy composites
Composites Part B-engineering, 2016Co-Authors: V Fiore, T Scalici, Francesco Nicoletti, Giuseppe Vitale, M Prestipino, A ValenzaAbstract:Abstract Several researchers have shown how Sisal fibres possess remarkable tensile properties that yield them good candidates as reinforcement in biocomposite materials. This work aims to evaluate the effect of an eco-friendly and cost effective surface treatment method based on the use of commercial sodium bicarbonate (i.e. baking soda) on properties of Sisal fibre and its epoxy composites. In particular, raw Sisal fibres were treated with a 10%w/w of sodium bicarbonate solution for different periods (24, 120 and 240 h), at room temperature. Changes occurring in Sisal fibres were characterized through scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis and helium pycnometer analysis. The mechanical characterization of Sisal fibre was carried out through single fibre tensile tests and a reliability analysis of the experimental data was performed. A mathematical model was also applied to investigate the relation between the transverse dimension of the fibres and their tensile properties. Interfacial adhesion of Sisal fibre with an epoxy matrix was investigated using single fibre pull out technique. Moreover, to deeper investigate the effect of the proposed treatment, epoxy based composites reinforced with short randomly oriented Sisal fibres were manufactured and characterized by means of quasi-static flexural tests. The experimental results showed that 120 h is the optimum time for treating Sisal fibre to achieve highest interfacial adhesion and mechanical properties with epoxy matrix.