RESUMO
The present paper describes the preparation and characterization of polysaccharides-based bio-composite films obtained by the incorporation of 10, 20 and 30 wt% birch cellulose (BC) within a glycerol plasticized matrix constituted by the corn starch (S) and chemical modified starch microparticles (MS). The obtained materials (coded as MS/S, respectively MS/S/BC) were further characterized. FTIR spectroscopy and X-ray diffraction were used to evidence structural and crystallinity changes in starch based films. Morphological, thermal, mechanical, and water resistance properties were also investigated. Addition of cellulose alongside modified starch microparticles determined a slightly improvement of the starch-based films water resistance. Some reduction of water uptake for any given time was observed mainly for samples containing 30% BC. Some compatibility occurred between MS and BC fillers, as evidenced by mechanical properties. Tensile strength increased from 5.9 to 15.1 MPa when BC content varied from 0 to 30%, while elongation at break decreased significantly.
Assuntos
Materiais Biocompatíveis/síntese química , Celulose/química , Plastificantes/química , Amido/química , Tartaratos/química , Betula/química , Materiais Biocompatíveis/química , Fenômenos Biomecânicos , Cristalização , Glicerol/química , Espectroscopia de Infravermelho com Transformada de Fourier , Resistência à Tração , Água/química , Difração de Raios X , Zea mays/químicaRESUMO
The study reported here presents a comparative screening of three medicinal plants including oregano (Origanum vulgare L.), lavender (Lavandula angustifolia) and lemon balm (Melissa officinalis) having the same geographical origin, the Southeast region of Romania, and growing in the same natural conditions. The contents of total phenolics and total flavonoids for the extracts of these were determined. Furthermore, the total antioxidant capacity was also evaluated. It was found that Origanum vulgare and Melissa officinalis extracts present the most effective antioxidant capacity in scavenging DPPH radicals, while Lavandula angustifolia is less active. High performance liquid chromatography-mass spectrometry analysis was used to identify the components of extracts. Major phenolic acids identified in the analysed species were ferulic, rosmarinic, p-coumaric and caffeic, while predominant flavonoids were quercetin, apigenin kaempherol, which were present as glucosides.
Assuntos
Antioxidantes/farmacologia , Flavonoides/análise , Lavandula/química , Melissa/química , Origanum/química , Fenóis/análise , Extratos Vegetais/análise , Folhas de Planta/química , Compostos de Bifenilo/metabolismo , Cromatografia Líquida de Alta Pressão , Radicais Livres/metabolismo , Concentração Inibidora 50 , Espectrometria de Massas , Picratos/metabolismo , RomêniaRESUMO
The effect of UV-visible light irradiation on the changes in color and chemical composition of the surfaces of Abies alba L. (fir, a softwood), non-modified and chemically modified, was studied. Chemical modification of the wood was performed by reaction with succinic anhydride in xylene at different concentration values. The wood samples were irradiated in air using a rotative device equipped with a middle pressure mercury lamp. Analysis of the color changes in wood surfaces during photo-degradation was carried out by measuring CIELAB parameters. Fourier transform infrared spectroscopy was used to study chemical changes caused by light irradiation. Irradiation modified physical and chemical characteristics of wood surfaces and resulted in rapid color changes, degradation of lignin and increased content of chromophoric groups on the wood surfaces. Color changes (DeltaE(ab)) correlate well with degradation of lignin.