Sisal chemically modified with lignins: Correlation between fibers and phenolic composites properties

Megiatto, Jackson D.; Silva, Cristina G.; Rosa, Derval dos Santos; Frollini, Elisabete

doi:10.1016/j.polymdegradstab.2008.03.011

Cited by 76 publications

(48 citation statements)

References 38 publications

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“…The fibers were then treated with a flow of ionized air blown the surface for 1, 3 and 5 h and immediately used to prepare the composite [2,5] . Fiber characterization: The untreated and treated fibers were characterized by determining the crystallinity index of the cellulose and subjecting them to inverse gas chromatography (IGC), as described elsewhere [1,12] . Tensile strength: Tensile strength was tested in fiber bundles 15 mm long and 0.5 mm in diameter, dried previously in a vacuum oven for 4 h, at 100 °C, and kept under vacuum, at room temperature.…”

Section: Ionized Air Treatmentmentioning

confidence: 99%

“…Pre-polymer synthesis: Phenolic pre-polymer was synthesized by mixing phenol (Synth, 99%), formaldehyde (Synth, 37%) and potassium hydroxide (Synth, 85%) (1.38:1.00:0.06) as described by Megiatto et al [1] . Cure reaction and composite preparation: Thermoset materials were prepared under conditions similar to those described by Silva et al [12] .…”

Section: Ionized Air Treatmentmentioning

confidence: 99%

“…However, matrix-fiber interactions could be further intensified, for example, by treating the surface of the fibers. In previous studies we have reported on chemical modifications of the surface of lignocellulosic fibers using furfuryl and polyfurfuryl alcohols, as well as using hydroxymethylated lignins [1] . Treatment of natural fibers with an alkaline solution (mercerization) is widely used.…”

Section: Introductionmentioning

confidence: 99%

“…Treatment of natural fibers with an alkaline solution (mercerization) is widely used. This treatment can increase the fiber surface roughness, separate the fiber bundles and remove cell wall components [1][2][3][4][5][6] . Usually, the wettability of the mercerized fibers is greater than that of unmodified fibers, thus improving strength of bonding between the fibers and the matrix [7] .…”

Section: Introductionmentioning

confidence: 99%

“…The dispersive component of surface free energy (g S D ) and specific interaction parameters describing the ability of the surface to act as an electron acceptor (AN s ) or electron donor (DN s ) are used to quantify the properties of the polymer surface. These surface parameters can be estimated by Inverse Gas Chromatography (IGC) [1,11,12] . In this study, IGC was used to characterize the surface properties of the fibers before and after modification (ionized-air and mercerization).…”

Section: Introductionmentioning

confidence: 99%

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Treatments of jute fibers aiming at improvement of fiber-phenolic matrix adhesion

2014

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Abstract:Composites based on a thermoset phenolic matrix and jute fibers were prepared and characterized. The fibers were alternatively treated with ionized air or aqueous alkaline solution (mercerization) with the aim of introducing changes in the morphology, dispersive component of surface free energy, g S D (estimated by Inverse Gas Chromatography, IGC) and the acid/base character of their surfaces, shown by their AN s /DN s ratio (estimated by IGC), and their degree of crystallinity. The final objective was to investigate the influence of these modifications on the adhesion at the jute fiber/phenolic matrix interface in the composites. The untreated jute fiber showed 50% crystallinity, g S D =18 mJ m -2 and AN s /DN s = 0.9 (amphoteric surface), tensile strength = 460 MPa and maximum elongation = 0.7%, while the respective composite had an impact strength of 72.6 J m -1 . The treatments positively modified the fibers and the adhesion at the interface was better in the composites reinforced with treated fibers than with untreated fibers. The best set of results was exhibited by the fiber treated with 10% NaOH [46% crystallinity, , AN s /DN s = 2.1 (acidic surface)] for further use as reinforcement of a phenolic matrix, but their partial degradation during the treatment decreased their tensile properties (395 MPa and 0.5% for tensile strength and maximum elongation, respectively) and their action as reinforcement (impact strength of the respective composite approximately 73 J m -1 ).

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Section: Ionized Air Treatmentmentioning

confidence: 99%

Section: Ionized Air Treatmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Treatments of jute fibers aiming at improvement of fiber-phenolic matrix adhesion

2014

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Phenolic Resins and Composites

Frollini

Castellan

2012

Wiley Encyclopedia of Composites

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One of the major contributions of phenolic resins is their use as a matrix in fiber‐reinforced composites to prepare materials with low fire‐smoke toxicity coupled with favorable economics and excellent properties. New formulations became available in the 1980s and were developed mainly to meet requirements of the mass‐transit fire code, which allowed the application of phenolic composites in new areas, such as in mass‐transit car interiors and architectural and marine components. These facts, along with their properties, led to a favorable conjunction for phenolic composites, making them widely used when the requirements of both public and worker safety are of primary importance. Currently, there are basically three types of phenolic resins: the traditional resoles and novolacs and the more recent polybenzoxazines. Lignin, a phenolic biopolymer present in wood and non‐wood plants, is a by‐product of the pulp and paper industry. The growing number of biorefineries in many countries, aiming to convert lignocellulosic wastes into fuels and chemical raw materials, will lead to the availability of large quatities of lignin, which gives it strategic importance as a substitute of phenol in phenolic resins. Aside from lignins, the condensed tannins, also obtained from renewable sources, are suitable to prepare a phenolic‐type polymeric matrix because of the presence of phenolic rings with a larger number of free positions where the electrophilic attack can occur. To decrease the dependence of phenol–formaldehyde (PF) resins on formaldehyde, and hence their formaldehyde emissions, phenolic–furfural (PFu) resins have been developed. In addition, the low vapor tension and low toxicity of glyoxal (OHC–CHO) solutions represent some of the advantages of using glyoxal instead of formaldehyde for many applications. Concerning the reinforcement of phenolic‐type composites, the properties required for a particular application, along with other questions such as cost, define the fiber to be used as reinforcement. The prerequisites for a given application define the fiber length, the diameter, and the need for surface modifications of the fiber, among other characteristics. In addition to the traditional fibers used (as glass, carbon, aramids), agro‐fibers can be mentioned, going by the growing interest this material has aroused. Lignocellulosic fibers are particularly interesting as plastic reinforcements because of their low cost, low density, process flexibility, and modest equipment requirement. These fibers are renewable, widely grown, moldable, anisotropic, nonabrasive, porous, viscoelastic, biodegradable, compostable, and reactive. Lignocellulosic fibers have many hydroxyl groups on the surface, mainly from cellulose and lignin, which may interact easily with the phenolic or lignophenolic polar matrices. The use of nanofibers or nanoparticles as reinforcement can be highlighted, as they can improve several properties of the related composite, such as thermal, flame, chemical, and moisture resistance, and decreased permeability. The set of properties of phenolic‐type matrices, as well as both the flexibility to make changes in their formulations and possible use of different reinforcements, in addition to their favorable cost/performance characteristics, place these materials in a prominent position in relation to other thermoset matrix composites.

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