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- Thermally modified wood exposed to different weathering conditions: A reviewPublication . Godinho, Delfina; Araújo, Solange; Quilhó, Teresa; Diamantino, Teresa; Gominho, JorgeOutdoor 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 protection
- Avaliação durabilidade de madeiras termo-modificadas à exposição atmosféricaPublication . Godinho, Delfina; Quilhó, Teresa; Diamantino, Teresa; Gominho, Jorge
- Exposição atmosférica de madeiras termo-modificadas – Avaliação da degradação superficialPublication . Godinho, Delfina; Araújo, Solange; Paiva, Teresa; Ferreira, Cristina; Quilhó, Teresa; Diamantino, Teresa C.; Gominho, JorgeA 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.
- Tropical mobola plum (Parinari Curatellifolia): a full characterization of wood and bark within the scope of biorefineriesPublication . Malengue, Abílio; Lourenço, Ana; Patrício, Helena; Costa, Ricardo A.; Quilhó, Teresa; Gominho, JorgeParinari curatellifolia is the main species used to produce charcoal in Angola. Its chemical, anatomical, and thermal prop- erties were analyzed. The bark is dark grey, rough, and corky, and the wood is brown to yellow-red. Compared to wood, bark fibers presented lower length, lumen, and wall thickness. There is not much difference between height and cell num- bers of rays. Sieve tube elements appear solitary or in small groups (2–3 cells), and vessels were of two diameter classes but diffuse-porous. Bark basic density was lower than wood (505 kg.m− 3vs. 580 kg.m− 3). The mean chemical composition from bark vs. wood of P. curatellifolia was ash (3.2% vs. 1.6%), total extractives (12.2% vs. 10.0%), total lignin (42.4% vs. 28.4%), and suberin 5.4%. Families identified by GC-MS from DCM extracts were predominated by fatty acids in wood and triterpenoid contents in bark. Bark and wood had higher antioxidant activity in FRAP and DPPH methods. The bark had a monomeric lignin composition richer in guaiacyl-units (25.9% vs. 22.5%) and lower syringyl-units (5.7% vs. 8.5%). Potassium was the most abundant mineral, while the least was cadmium found in wood and bark. Regarding ther- mal properties, bark presented higher moisture content (9.0% vs. 8.0%), ash (3.33% vs. 1.61%), total volatiles (27.5% vs. 20.7%), lower fixed carbon (69.1% vs. 77.7%) and higher heating value (20.9 MJ/kg vs. 19.1 MJ/kg). According to these characteristics, both biomasses are interesting for developing more value-added products (e.g., charcoal, bio-chemicals with phytochemistry and pharmacology activities) besides burning under the context of biorefineries.
- The behavior of thermally modified wood after exposure in maritime/industrial and urban environmentsPublication . Godinho, Delfina; Ferreira, Cristina; Lourenço, Ana; Araújo, Solange; Quilhó, Teresa; Diamantino, Teresa C.; Gominho, JorgeNatural and thermally modified Pine, Ash, and Acacia woods were exposed in two different en- vironments: urban and maritime/industrial. The weathering effects were evaluated during 24 months regarding color, chemical, and structural changes. In all wood species, thermal modifi- cation induced color, chemical, and structural changes. All woods became darker (Pine ΔL*: 32.01; Ash ΔL*: 36.83; Acacia ΔL*: 27.50), total extractives content increased (Pine: 19 %; Ash: 32 % and Acacia: 18 %), and the samples presented deformation and damaged cells. Total lignin was not significantly changed, although there were detected changes in lignin, namely the reduction of G-units in Pine (≈2 %) and reduction of S/G ratio in Acacia (≈0.04 %). Ash remained almost the same. After weathering, modified woods suffered fewer color changes, indicating that the thermal modification could improve the resistance to color change. Acacia wood, when exposed to maritime/industrial conditions, revealed a higher color change (ΔE: 35.7 at 24 months) when compared with urban conditions (ΔE: 23.5 at 24 months). Delignification, possibly caused by photodegradation, occurred in all wood samples, and the loss of extractive happened, perhaps caused by rain. Modified woods were slightly less resistant to weathering in maritime/ industrial environments. Some structural damage, namely cracked cells, the appearance of molds, blue staining, and particle deposition, was observed. The thermal modification enables color stabilization but does not seem to improve the weathering resistance in all studied wood species. Exposure to the different environments did not lead to significant differences in the morphology and chemical composition of the three natural and modified wood species.
- Thermally modified wood of Acacia melanoxylon preliminary resultsPublication . Godinho, Delfina; Lourenço, Ana; Araújo, Solange de Oliveira; Quilhó, Teresa; Diamantino, Teresa; Gominho, JorgeDue 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.
- Avaliação da resistência à exposição atmosférica de madeiras termo-modificadasPublication . Godinho, Delfina; Araújo, Solange; Paiva, T.; Ferreira, C.; Quilhó, Teresa; Gominho, JorgeEm sentido lato pode-se afirmar que a madeira sofre biocorrosão, o que constitui um fator limitante para a sua aplicação no exterior, caso não haja uma proteção adequada. A termo-modificação 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 provoca alterações nas propriedades mecânicas, nomeadamente a diminuição do módulo de elasticidade (MOE) e de rotura (MOR). O presente trabalho teve como objetivo 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, a acácia (Acacia melanoxylon) e o freixo (Fraxinus excelsior). Amostras destas madeiras termo-modificadas foram depois, expostas durante 2 anos em duas estações de ensaio representativas de dois ambientes diferentes, no Lumiar (ambiente urbano) e em Sines (ambiente marítimo/industrial). A avaliação da resistência da madeira à exposição atmosférica, incluiu a recolha de amostras ao longo de 24 meses de exposição e a análise das superfícies das amostras por espetroscopia de infravermelho com transformada de Fourier (FTIR) com acessório de refletância total atenuada (ATR) e por microscopia eletrónica de varrimento (SEM) com um espectrómetro de raios X de energia dispersiva (EDS) associado. Os resultados preliminares indicam um comportamento semelhante para todas as madeiras expostas em ambas as estações. Verificou-se, contudo, que embora se tivesse observado o aparecimento de fendas e de inúmeras partículas na superfície de todas as madeiras, houve uma 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.