Influence of juvenile wood proportion on density and modulus of elasticity in softwood boards for structural use: a preliminary study.

Juvenile wood (JW) can influence the performance of structural boards since it presents lower physical and mechanical properties. This study aimed evaluate the influence of JW proportion on density and modulus of elasticity (MOE) on boards for structural use. Pinus taeda logs 30 years old, had growth rings manually counted (on the pith to bark direction), and the first six rings were painted with color red (0-6), followed by blue (6.1-12), orange (12.1-18), green (18.1-24), and yellow (over 24.1), successively, and cut into boards. The proportion of each color was obtained by analysis of the transversal areas of boards with software. MOE was obtained by a nondestructive test. Multiple linear regression models were applied with 5% of significance. The estimated MOE indicates that boards with at least 57% of orange and green colors (between 12.1 - 24 years old) can achieve the minimum MOE value for using as structural as well as boards without red color but with the presence of green and yellow can have MOE bigger than 7000 MPa. The study indicates a behavior tendency about which proportion and mixed colors can affect the MOE of the board to be classified as structural.

Sludge Fiber Waste and Kraft Lignin Powder as Fillers in Polylactic Acid Biocomposites: Physical, Mechanical, and Thermal Properties.

In this investigation, sludge fibre waste (SFW) and Kraft lignin powder (KLP) are introduced into polylactic acid (PLA) matrix biocomposites. These alternative materials allow for both the reuse of fibre waste from paper mill sludge and a reduction in the amount of high-cost biopolymer used in the same volume. Proportions from 10 to 40 wt.% of SFW with the addition of 2.5% and 5% of KLP are incorporated in PLA by extrusion and injection moulding. The thermogravimetric properties, water absorption, tensile and flexural properties, and morphology of the fabricated biocomposites were investigated. According to the results, KLP contributes to thermically stabilising the loss resulting from the incorporation of SFW. Flexural and tensile tests reveal a more pronounced decrease in strength with an SFW ratio above 10%. The modulus of elasticity increases significantly with an SFW ratio above 20%. The strength properties are stabilised with the addition of 5% KLP. The addition of KLP presents a tendency to reduce water absorption obtained by the incorporation of SFW into biocomposites. Scanning electron micrographs evidence that KLP improves the interfacial adhesion by reducing the voids between fibres and PLA.

Avaliação das propriedades de painéis aglomerados produzidos com resíduos de serrarias de nove espécies de madeiras tropicais da Amazônia / Evaluation of the properties of particleboard made from sawmill waste of nine tropical wood species of Amazon

Esta pesquisa teve como objetivo avaliar a qualidade de painéis aglomerados produzidos com resíduos de processamento em serraria de nove espécies de madeiras tropicais da Amazônia. As espécies estudadas foram: Scleronema micranthum Ducke (Cardeiro), Ecclinusa guianensis Eyma (Caucho), Scleronema sp. (Castanha-de-paca), Copaifera multijuga Hayne (Copaíba), Ocotea sp. (Louro), Ocotea guianensis Aubl (Louro-espinho), Caryocar villosum Pers. (Piquiarana), Couratari oblongifolia Ducke & R. Knuth (Tauari) e Virola surinamensis Rol. Warb (Virola). Foram produzidos painéis experimentais com densidade nominal de 0,75 g.cm-3, utilizando a resina uréia-formaldeído na proporção de 8 por cento de sólidos - base peso seco das partículas. Os painéis foram prensados com pressão específica de 4,0 MPa, temperatura de 160 ºC e tempo de prensagem de oito minutos. As avaliações dos resultados de ensaios obtidos nesta pesquisa indicam a viabilidade técnica de utilização das nove espécies provenientes de florestas tropicais da Amazônia na produção de painéis de madeira aglomerada, com destaque para Ecclinusa guianensis Eyma (Caucho) que, de uma forma geral, apresentou melhores resultados de propriedades físico-mecânicas.

This research was developed to evaluate the quality of particleboards manufactured from sawmill waste of nine tropical wood species of Amazônia. The following species were studied: Scleronema micranthum Ducke (Cardeiro), Ecclinusa guianensis Eyma (Caucho), Scleronema sp. (Castanha-de-paca), Copaifera multijuga Hayne (Copaíba), Ocotea sp. (Louro), Ocotea guianensis Aubl (Louro-espinho), Caryocar villosum Pers. (Piquiarana), Couratari oblongifolia (Tauari) e Virola surinamensis Rol. Warb (Virola). The experimental boards were manufactured with the nominal density of 0.75 g.cm-3, using the urea-formaldehyde resin in the proportion of 8 percent of solid content based on oven dried wood particles. The boards were pressed at the specific pressure of 40 kgf/cm², temperature of 160 ºC and press time of eight minutes. The evaluations of test results obtained in this study indicate the potential use of the nine species from Amazon rainforest in the production of particleboard, highlighting Ecclinusa guianensis (Caucho) that, in general, showed better results of physical and mechanical properties.