Thermally modified wood exposed to different weathering conditions: A review

ReviewOutdoor wood applications are exposed to several different biotic and abiotic factors, and for that reason, they require protection to increase their service life. Several technologies of wood protection are already commercialized. One of these technologies is thermal modification, which refers to the structural, mechanical, and chemical transformations occurring in the lignocellulosic material when gradually heated up to specific temperature ranges. In the past few years, several researchers have undertaken weathering resistance evaluations on different wood species. Some cases have considered natural exposure in different countries with different climatic conditions, while others focused on artificial exposure under UV and xenon radiation tests. Most works evaluated the weathering effects on the chemical, mechanical and physical, and anatomical shifts compared to the original characteristics of the material. This review has established a considerable lack of studies in the bibliography focusing on abiotic factors, such as the industrial and maritime environment, or even isolated climatic factors such as salt spray (simulating maritime environments) or pollutant gases (simulating industrial environments). This lack of information can be an opportunity for future work. It could help to understand if thermally modified wood is or is not sensitive to pollutant gases or salinity, or to a combination of both. By knowing the degradation mechanisms caused by these factors, it will be possible to study other forms of protectioninfo:eu-repo/semantics/publishedVersio

An Integrated Similarity Analysis of Anatomical and Physical Wood Properties of Tropical Species from India, Mozambique, and East Timor

Tropical species are highly valued timber sources showing a large diversity of wood characteristics. Since there are major concerns regarding the sustainability of these tropical species in many tropical regions, knowledge of the variability in wood properties is therefore a valuable tool to design targeted exploitation and to enlarge the wood resources base, namely by identifying alternatives for CITES-listed species. In this study, 98 tropical wood species belonging to 73 genera from India, Mozambique, and East Timor were investigated regarding wood anatomy and physical properties. Numerical taxonomy, by means of cluster analysis and principal component analysis grouped species with anatomical and physical similarities from different geographical origins. In addition to wood density, ray and vessel characteristics as well as wood moisture and wood shrinkage properties explained the main variability of these species. The contribution of wood color patterns was highlighted as consistently separating the Mozambique woods. A distinct geographical pattern was not observed, reinforcing that species from India, Mozambique, and East Timor show similar anatomical and physical wood properties, which could be useful to increase timber trade diversity. The multivariate analysis showed that species from Mozambique, such as Morus mesozygia, and Millettia stuhlmannii and Swartzia madagascariensis, could be alternatives for the CITES-listed species Cedrela odorata and Dalbergia melanoxylon, respectivelyinfo:eu-repo/semantics/publishedVersio

Xiloteca virtual - colecção de madeiras da India portuguesa

Congresso Florestal Nacional: A floresta e as gentes - Actas das ComunicaçõesCom base na colecção de amostras de madeira existente na xiloteca e respectiva laminoteca do Centro de Estudos de Tecnologia Florestal (IICT), apresenta-se uma base de dados de madeiras da Índia Portuguesa, que inclui 17 espécies xilógenas, selecionadas por serem das mais abundantes e com maior interesse em Goa. O objectivo deste trabalho é a criação de uma Xiloteca Virtual, que reuna toda a informação existente sobre as madeiras, prevendo-se uma série de interacções que possibilitem dar rápida resposta a questões concretas do utilizador, como sejam a identificação botânica, as propriedades anatómicas e físicas da madeira e ainda os diferentes usos. Para cada espécie indica-se a família, o nome botânico, os nomes indígenas, a distribuição geográfica e as características da madeira. A caracterização da madeira inclui os aspectos gerais tais como, a cor, o desenho, a textura, o estudo anatómico, com as descrições macro e microscópicas e as propriedades físicas (densidade e retracção) com interesse na identificação e utilização final da madeira. Exemplifica-se o trabalho com saídas tipo, referente ao aspecto geral da madeira, propriedades anatómicas e físicas, fotomicrografias e possíveis interacções

Avaliação durabilidade de madeiras termo-modificadas à exposição atmosférica

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Thermally modified wood of Acacia melanoxylon preliminary results

Due to the urban development and the continuous growth of cities, architects, engineers, and constructors are choosing sustainable materials. Wood is a natural, sustainable, and low-carbon material. However, wood presents some disadvantages (e.g. hygroscopicity and anisotropy), that can be overcome by thermal treatments [1]. The wood thermal modification only requires temperature and an oxygen-free atmosphere, it does not use any kind of chemical products and improves some wood properties such as dimensional stability, water resistance, and biological attack resistance [1]. Acacia melanoxylon is among the most widespread invasive plants in Europe. Today, Acacias are widely naturalized and have become an environmental problem in Southwestern Europe, particularly in Portugal. Its presence can be a threat to native species and has been declared ‘‘invaders’’ due to its rapid growth rate, prolific production of seeds with high longevity, and germination stimulated by fire. Acacia wood has very interesting mechanical properties which can be used in building construction, façades, walkways, and decks, among others. This study aimed to thermally modify Acacia wood in collaboration with a Portuguese company, Santos & Santos. Then the unmodified (A) and modified (MA) woods were exposed to weathering in two different environments (urban and industrial/maritime) and the color, chemical, and morphological changes were evaluated over time. The wood color was determined by a portable spectrometer measuring the CIELab parameters. The summative chemical analysis (e.g. total extractives and lignin contents) was made and the lignin monomeric composition was accessed by analytical pyrolysis (Py-GC/MS). Additionally, the samples were characterized by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The treatment induced a decrease in the soluble lignin content (1.1% for A and 0.70% for MA) and an increase in Klason lignin (17.2% for A and 27.0% for MA), which can be caused by a lignin degradation during the thermal treatment [2]. Py-GC/MS showed a decrease in S/G ratio in modified wood (2.2 vs. 1.7), caused by an increase of G-lignin units and a decrease of S-units in the modified acacia wood. This could be explained by lignin modifications during the treatment [2]. Through SEM/EDS analysis, some cracks in fibers and particles were detected in samples exposed to both environments. Some deposition of dust, aerosols from pollution, and salt particles were found in woods exposed to the industrial/maritime environment. Likewise, woods from the urban environment also had some deposition of dust. The study is still running and for that reason is not possible to present all the results, namely those from the analysis of the weathered samples.info:eu-repo/semantics/publishedVersio

Quercus rotundifolia bark as a source of polar extracts: structural and chemical characterization

Quercus rotundifolia bark was studied regarding anatomical, chemical, and antioxidant properties from trees in two sites in southern Portugal and are here reported for the first time. The general structure and anatomy of Q. rotundifolia bark showed a rhytidome with sequential undulated and anastomosed periderms with a small proportion of cork, while the phloem included broad rays with strong cell sclerification, groups of sclereids with embed large prismatic crystals, and abundant druses in parenchyma cells. The mean chemical composition was 15.5% ash, 1.6% dichloromethane extractives, 6.4% ethanol and 9.3% water extractives, 3.0% suberin, 30.5% total lignin, and 33.8% carbohydrates. Carbohydrates included mainly glucose (50.7% of total monomers) and xylose (23.8%), with uronic (3.0%) and acetic acids (1.0%). Suberin was mainly composed of !-hydroxyacids (48.0% of all compounds) and ,!-diacids (19.5%). The main compounds found in the lipophilic extracts were triterpenes (43.6%–56.2% of all compounds) and alkanoic acids (32.7%–41.7%). Phenolic content was high especially in the ethanol extracts, ranging from 219.5–572.9 mg GAE/g extract and comprising 162.5–247.5 CE/g extract of flavonoids and 41.2–294.1 CE/g extract of condensed tannins. The extracts revealed very good antioxidant properties with IC50 values of 4.4 g ethanol extract/mL and 4.7 g water extract/mL. Similar anatomical, chemical, and antioxidant characteristics were found in the bark from both sites. The high phenolic content and excellent antioxidant characteristics of polar extracts showed holm oak barks to be a promising natural source of antioxidants with possible use in industry and pharmaceutical/medical areasinfo:eu-repo/semantics/publishedVersio

The anatomy as a tool for the identification of the bark of Pterocarpus angolensis and Terminalia sericea

Pterocarpus angolensis and Terminalia sericea are two African species with medicinal potential. Despite the importance of their bark as a powerful astringent to treat various diseases it is poor described. In order to provide referential information for correct identification and standardization of the plant material, bark samples from each two species were collected and analyzed under light and electron microscopy. Some important anatomical features to identification were: the sclerenchyma tissue mostly in form of fibre-sclereids and the large secretory cells arranged in conspicuous rows or tangential bands in the conducting phloem in P. angolensis; the crystalliferous cells arranged in very regular tangential rows (druses) and the occurrence of large crystal cells near or including the tangential fibre bundles in T. sericea bark.The results obtained show that the anatomy of the bark can be used as an important subsidy in identification and standardization of the studied species contributing the scientific knowledge for more effective forms of scrutiny in preventing commercial adulteration of species

Narrating codex history: the case study of a psalter-hymnal from Alcobaça Monastery, Portugal

This article provides the first in-depth study of historic content and materials used in the production of a liturgical codex from the collection of manuscripts of the Monastery of Alcobaça: the Psalter-hymnal (Lisbon, National Library, Alc. 11). To answer provenance questions and trace the manuscript’s history, a multidisciplinary team studied the entire procedure of making the codex, which went from in-depth textual, liturgical, and codicological analyses, to examining material composition and bookbinding methods with complementary analytical techniques. The team was able to track the manuscript’s historical trajectory through successive additions and interventions/alterations. Interpretation of the historic information and the resulting technical data confirmed the belief that this is a twelfth-century manuscript produced in the scriptorium of Alcobaça and underlined the role that the manuscript played in this Cistercian monastery during the Middle Ages, and possibly throughout the following centuries. This led the team to approach the codex’s “cultural significance” and perceive later alterations and interventions as evidence of the monks’ intensive use of this manuscript and the great care they took to preserve their monastic library. The new data and knowledge acquired about this precious codex proved to be fundamental for future digital access policy definition and the conservation making decisioninfo:eu-repo/semantics/publishedVersio

Variabilidade anatómica da teca (Tectona grandis) de Timor-Leste

A teca (Tectona grandis) é uma importante espécie indígena do sudeste asiático, produtora de madeira nobre com excelente qualidade e grande procura no mercado mundial pela sua resistência, durabilidade e beleza. Estas propriedades dependem, entre outras, da estrutura e variabilidade da madeira, na espécie, entre árvores e na árvore consoante as condições ambientais. Não existem estudos publicados sobre a variabilidade anatómica da madeira para a teca proveniente de Timor-Leste. O estudo incidiu em três árvores, em amostras retiradas a três níveis de altura total e da medula para a periferia da árvore. Realizaram-se observações à lupa e ao microscópio e foram determinados: n.º e área de vasos por anel de crescimento, comprimento, largura e espessura da parede de fibras, utilizando um sistema de análise de imagem. Os resultados indicam que da base para o topo da árvore houve um aumento do número médio e um decréscimo da área média de vasos por anel de crescimento, do comprimento e largura média das fibras. Radialmente, da medula para a periferia, diminuiu o número e aumentou a área média de vasos por anel de crescimento, o comprimento, a largura e a espessura da parede das fibras

Exposição atmosférica de madeiras termo-modificadas – Avaliação da degradação superficial

A madeira é um material biodegradável e isso constitui um fator limitante para a sua aplicação no exterior, caso não haja uma proteção adequada. Neste sentido, o tratamento térmico é um dos métodos utilizados para aumentar a durabilidade da madeira. Uma das vantagens deste processo é que não requer qualquer tipo de adição de químicos. A temperatura utilizada no processo induz a alterações químicas dos constituintes da matriz celular que promovem o aumento da durabilidade aos agentes bióticos e abióticos, mas também a alterações estruturais, que provocam redução das propriedades mecânicas [1].O presente trabalho teve como objectivo a avaliação da durabilidade da madeira termo-modificada de 3 espécies: o pinheiro-bravo (Pinus pinaster), a principal espécie utilizada pela indústria portuguesa de madeira sólida, e ainda acácia (Acacia melanoxylon) e o freixo (Fraxinus excelsior), espécies com potencial valorização da madeira sólida como matéria-prima. A termomodificação foi efectuada pela empresa Santos & Santos Madeiras (usando uma temperatura média de 210°C). Amostras destas madeiras termomodificadas foram depois, expostas ao envelhecimento natural durante 2 anos em duas estações de ensaio representativas de dois ambientes diferentes, no Lumiar (ambiente urbano) e Sines (ambiente marítimo/industrial).A avaliação do processo de envelhecimento natural incluiu a recolha de amostras ao longo do tempo (0, 9, 12 e 24 meses) onde foram avaliadas: i) a medição da cor ao longo do tempo, através do sistema CIELab; ii) análise das superfícies das amostras por espectroscopia de infravermelho com transformada de Fourier (FTIR) com acessório de refletância total atenuada (ATR) e por microscopia eletrónica de varrimento (SEM) associada a um espectrómetro de raios X de energia dispersiva (EDS).Os resultados preliminares apontam que as madeiras expostas apresentaram um comportamento semelhante em ambas as estações: as madeiras naturais ficaram mais escuras e as termomodificada mais claras, pelo facto de as naturais serem mais suscetíveis ao ataque de fungos. O aparecimento de fendas e de inúmeras partículas ocorreu na superfície de todas as madeiras, embora com maior incidência nas expostas em Sines (zona com maiores variações de humidade e temperatura), nomeadamente nas amostras de 9 meses onde se observaram na superfície cristais de NaCl, devido à proximidade desta estação da orla marítima. Os espetros de FTIR-ATR indicam ter ocorrido diminuição do teor em hemiceluloses e de lenhina na superfície das amostras principalmente nas amostras recolhidas após os 24 meses de exposição, tanto em Sines como no Lumiar.info:eu-repo/semantics/publishedVersio