The bark of the tree species Myrcia eximia DC., which occurs in secondary forests in the Brazilian Amazon, is described for the first time. The aim was to provide a broad knowledge of its composition, to add value, and to direct uses to the bark of this species based on its polyphenolic content and antioxidant capacity. The bark is formed by conducting phloem, nonconducting phloem, and rhytidome. In addition, dead phloem occurs between the periderms. The average chemical composition of the bark was 45.6% total extractives, 1.4% suberin, 1.7% ash, and 21.1% lignin. The ethanol-water extract had a high content of flavonoids and condensed tannins [300.8 and 877.3 mg catechin equivalents (CE) g−1 of the extract, respectively]. High-performance liquid chromatography (HPLC) was used to quantify the presence of rutin, quercetin, and gallic, ferulic, and o-coumaric acids. The bark extract showed strong 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radical scavenging activity, which was superior to that of the commercial antioxidant butylated hydroxytoluene (BHT), with an IC50 of 85.2 μg mL−1. Based on these results, it is evident that the bark of M. eximia from the Brazilian Amazon rainforest is a new and potential natural source of phenolic compounds and antioxidants, and its extracts can be used in the food and pharmaceutical industry and in various condensed tannin-based products.
Adhesives based on vegetable tannins are already a reality in the market. However, their use is still limited due to their low mechanical resistance and weak humidity resistance. Cellulose nanofibrils (CNFs) are being used as reinforcing materials in various composites, resulting in an improvement of mechanical proprieties in general. The objective of this work was to evaluate the incorporation of CNFs in adhesives made of tannins obtained from the Angico tree (Anadenanthera peregrine). Concentrations of nanofibrils at 1, 5, and 10% were added to the adhesives on a dry basis. Tests of viscosity, pH, solids content, and gel time were performed to determine the physical proprieties of the adhesives. The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Raman spectra measurements were also determined to understand the interaction between tannins and CNFs. Thermogravimetric analyses (TGA) were carried out to determine the thermal resistance of the composite. The FTIR and Raman characterization identified some differences in the peaks in the chemical composition of the adhesives with different percentages of CNFs. The adhesives showed no different decomposition in the thermogravimetric analyses. The shear strength in the glue line of the adhesive with 5% of CNFs in Toona ciliata woods was determined. Among all the adhesives analyzed, the one with 5% of CNFs produced an improvement in the mechanical resistance and humidity resistance on the glue line.
No presente estudo foram caracterizadas as propriedades tecnológicas de painéis de fibras de média densidade (MDF), em diferentes horários de produção em uma linha industrial brasileira, com o objetivo de avaliar a variabilidade tecnológica das chapas e sua qualidade em relação à norma técnica comercial. Painéis MDF confeccionados com fibras de Eucalyptus spp. (70%), Schizolobium parahyba (20%) e madeiras residuais de serraria (10%), aglutinados com resina ureia-formaldeído foram coletadas em intervalos de duas horas de um turno de produção da empresa. Foram determinadas às propriedades físicas (umidade, densidade aparente, absorção superficial, absorção de água, inchamento em espessura e taxa de não retorno de espessura) e resistência mecânica (flexão estática, dureza janka, tração perpendicular e arrancamento de parafuso). Os painéis de início e final do turno foram submetidos ao ciclo de envelhecimento acelerado, sendo avaliados posteriormente à densidade, tração e flexão estática. Do total das propriedades avaliadas nos painéis MDF, um percentual de 55% não apresentaram variações entre os horários de produção, e se enquadraram aos valores da norma. Apenas as propriedades de inchamento em espessura (IE 24h) e tração em 80% dos horários, não atenderam aos valores estipulados pela ABNT NBR 15316-1, variando de 11,2 a 15,6% e 0,42 a 0,62 N/mm², respectivamente, entre o início e o final do turno. O envelhecimento acelerado promoveu diminuição expressiva na qualidade das chapas. Os painéis MDF estudados apresentam bom desempenho tecnológico para uso em ambiente seco, e sua variação tecnológica decorreu do uso de fibras de diferentes madeiras na produção das chapas.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.