Photodegradation of sugarcane bagasse fibers: influence of acetylation or grafting UV-absorber and/or hindered nitroxide radical on their photostability

Abstract

um radical nitróxido do tipo piperidiniloxi (3). As fibras FBC-AP foram também acetiladas com anidrido acético. A fotossensibilidade dessas fibras à radiação UV foi avaliada comparativamente, empregando coordenadas Lab color, assim como pela monitoração dos seus espectros de reflectância difusa no UV-Visível. As fibras FBC mostraram-se fotoestáveis, enquanto que as FBC-AP apresentaram certa sensibilidade à radiação UV. A estabilidade das FBC deve-se à presença de unidades do composto fotoestável p-hidroxifenilpropano, proveniente dos fragmentos de lignina. As fibras FBC enxertadas e não-enxertadas apresentam comportamentos similares frente à radiação UV e Visível enquanto que as FBC-AP enxertadas são fotoestabilizadas pela presença de 2 ou 4, ou ambos. A acetilação das fibras FBC-AP induz a fotoestabilização, em adição a certo efeito de fotoalvejamento. O fotoalvejamento foi também apresentado por medidas de emissão de fluorescência. Como conseqüência dessas observações, as fibras FBC devem ser consideradas como materiais lignocelulósicos com elevado potencial de aplicação em ambientes externos.Unbleached (SCB) and peroxide bleached (PB-SCB) sugarcane bagasse fibers were grafted with hydroxyphenylbenzotriazole UV absorber (1) and/or hindered nitroxide radical of piperidinyloxy type (3). PB-SCB fibers were also acetylated with acetic anhydride. The photosensitivity of the various fibers to UV light was comparatively evaluated using Lab color coordinates and by monitoring their UV-Visible diffuse reflectance spectra. SCB fibers were found to be photostable whereas PB-SCB fibers presented some sensitivity to UV light. The stability of SCB fibers was attributed to the presence of photostable para-hydroxyphenylpropane units in SCB lignin. The grafted and non-grafted SCB fibers showed similar behaviors against UV-Visible light whereas grafted PB-SCB were photostabilized by the presence of 2 or 4 or both. Acetylation of PB-SCB fibers induced photostabilization in addition to some photobleaching effect. The photobleaching was also revealed by fluorescence emission studies. As a consequence of these observations, SCB fibers might be considered to have a high potential for lignocellulosic materials to be used outdoors. Keywords: bagasse fibers, photodegradation, photoprotection IntroductionFibers obtained from biomass are cheap, non-toxic and easily recyclable. Their use contributes to environmental protection.1 Among them, sugarcane bagasse is a poorly valorized waste residue from sugar and alcohol industries.It is usually burnt for energy supply. Valorization of this material includes pulps, 2 thermoset composites, 3 outdoor usages, 4 cement strengtheners 5 and materials for cleaning water from heavy metal contaminants. 6 Another important research field involving this material is its bioconversion to produce protein rich animal aliment, enzymes, amino acids and pharmacological compounds.7 Lignocellulosic materials are sensitive to irradiation in the range from 764 Ruggiero et al. J. Braz. Chem. Soc. 300 to 400 nm a...

Vegetal fibers in polymeric composites: a review

“…Ruggiero et al [78] analyzed unbleached (SCB) and peroxide bleached (PB-SCB) sugarcane bagasse fibers grafted with hydroxyphenylbenzotriazole UV absorber (1) and/or hindered nitroxide radical of piperidinyloxy type [3] . PB-SCB fibers were also acetylated with acetic anhydride.…”

Hydrophobic treatment of natural fibers and their composites—A review

“…Only slightly improved initial delignification by sodium chlorite grafting, but in the presence of only 0.8% lignin, the grafting efficiency was doubled [131]. Bleached and unbleached sugarcane fibers were grafted with hydroxy phenyl benzotriazole UV absorber and nitroxide radical of piperidinyloxy followed by treatment with acetic anhydride [135].…”

Mechanical properties of trays based on starch of native plant species and fiber of agroindustrial wastes

“…En este trabajo, las diferentes fibras provenientes de los residuos agroindustriales, como el bagazo de caña de azúcar o la peladilla de espárrago, fueron utilizadas como componentes en las bandejas de almidón para reducir su sensibilidad a la humedad. Por otra parte, al ser barato, no tóxico, y fácil de reciclar, el uso de este tipo de material contribuye en la protección del medio ambiente (Ruggiero et al, 2006). Así, el objetivo de este trabajo fue evaluar el efecto de la adición de fibras naturales obtenidas de residuos agroindus-triales en la densidad, el gramaje y las propiedades mecánicas de las espumas termoprensadas elaboradas de almidón de las especies nativas camote, oca y arracacha.…”