Departamento de Engenharia de Madeiras (DEM)
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- Ensino Superior e a Realidade Empresarial: em busca do adequado interposicionamentoPublication . Figueiredo, António JoséO grande "divórcio" que tem caracterizado o interrelacionamento entre ensino superior e a realidade do jogo económico tem - salvo honrosas e escassíssimas excepções - resistido tenazmente quer a críticas quer às variadas tentativas dos "conselheiros matrimoniais" mais empenhados. Se, por um lado, a realidade empresarial se queixa do grande desajuste entre a formação com que os alunos saem das nossas escolas de ensino superior e as reais necessidades das empresas e demais organizações, por outro assiste-se à lamentação das escolas em relação à falta de interesse com que empresários e outros responsáveis encaram a sua participação - supostamente activa - nos conselhos consultivos e, de um modo geral, sempre que são chamados a sugerir, colaborar, ou seja, a contribuir para o almejado ajustamento de posicionamentos.
- PRODESIGN - Desenhadores com Qualificação em Design de Mobiliário Um projecto Leonardo da VinciPublication . Santos, AntónioO ISPV, por intermédio do Departamento de Engenharia de Madeiras - DEMad, encontra-se integrado, no âmbito do programa comunitário Leonardo da Vinci, no projecto "PRODESIGN - Desenhadores com Qualificação em Design de Mobiliário", que se encontra a ser desenvolvido por uma parceria transnacional que inclui as seguintes instituições, ligadas directa ou indirectamente à área do design de mobiliário:
- Technological improvement of Portuguese eucalypt and pine woods by heat treatmentPublication . Esteves, BrunoHeat treatments for technological improvement of wood were made in the presence of air using Eucalyptus globulus. The heat treatment was made using an oven during 2 to 24 h and temperatures of 170 ºC, to 200 ºC. Mass losses increased with treatment time and temperature. Anti Shrinking Efficiency (ASE) between treated and untreated samples was calculated at 35%, 65% and 85% relative humidity for radial and tangential directions. Bending strength and MOE were also determined. Equilibrium moisture content of heat-treated wood decreased by 67%. 87%Radial ASE35% for Tangential ASE35% was usually higher than radial. ASE65% and ASE85% showed behaviour similar to ASE35% but smaller. All ASE values increased with temperature and treatment time. Bending strength and MOE decreased with mass loss.
- Pulping yield and delignification kinetics of heartwood and sapwood of maritime pinePublication . Esteves, Bruno; Gominho, J.; Rodrigues, J.C.; Miranda, I.; Pereira, H.In maritime pine (Pinus pinaster Ait.), heartwood represents a substantial part of the tree stem at final harvest age (80 years) corresponding to 42% at the base of the stem wood diameter and decreasing upward. The rate of heartwood formation was estimated at 0.35 rings/year, beginning at 18 years of age. Differences in the chemical composition between heartwood and sapwood were mainly in the extractives, 19.7% and 5.8%, respectively. The lignin content was 23.1% and 24.5% in the heartwood and sapwood, respectively. Pulping yield of the heartwood was lower than that of the sapwood (40.0% vs. 49.7%) and was negatively correlated with the extractives content. Extraction of heartwood prior to pulping increased the pulp yield and the delignification (lower residual lignin in pulps). Pulping kinetics showed lower yields for heartwood at all pulping stages, the difference occurring especially in the initial reaction phase. However, delignification rate constants were similar for heartwood and sapwood (3.1 1022 min21 and 2.7 1022 min21 for the main delignification phase for sapwood and heartwood, respectively), with a lower activation energy for sapwood (68.3 vs. 90.0kJ.mol21). The presence of heartwood decreases the raw-material quality for pulping and this should be taken into account when harvesting trees for pulping processes.
- Influence of steam heating on the properties of pine (Pinus pinaster) and eucalypt (Eucalyptus globulus) woodPublication . Esteves, Bruno; Velez Marques, António; Domingos, Idalina; Pereira, HelenaHeat treatment of Pinus pinaster and Eucalyptus globulus woods, two important species in Portugal, was made in the absence of air by steaming, inside an autoclave, for 2 to 12h at 190 ºC to 210ºC. Mass losses increased with treatment time and temperature reaching 7.3% for pine and 14.5% for eucalypt wood. The wood behaviour with moisture was improved. The equilibrium moisture content decreased by 46% for pine and 61% for eucalypt, the dimensional stability increased (maximum anti-shrinking efficiency in the radial direction of 57% and 90% for pine and eucalypt respectively) and the surface wettability was lowered. In relation to mechanical properties, the modulus of elasticity was little affected (maximum decrease of 5% for pine and 15% for eucalypt) but the bending strength was reduced (by 40% at 8% mass loss for pine and 50% at 9% mass loss for eucalypt wood). The variation of properties was related to treatment intensity and mass loss but significant improvements could already be obtained for a 3-4% mass loss without impairing the mechanical resistance. The response of eucalypt was higher than that of pinewood. Heat treatment of eucalypt wood shows an interesting potential to improve the wood quality for solid timber products.
- Improvement of technological quality of eucalypt wood by heat treatment in air at 170-200ºCPublication . Esteves, BrunoEucalypt wood is a low value wood considered a non durable species with low dimensional stability, used almost exclusively for pulp and paper or as firewood. The heat treatment was made in an oven in the presence of oxygen during 2 to 24 h and temperatures of 170-200ºC. Mass loss with treatment, equilibrium moisture content, dimensional stability measured as ASE in radial and tangential directions and at 35%, 65% and 85% relative humidity, MOE, bending strength and wettability were determined. Mass loss increased with treatment time and temperature reaching 9.5% for wood treated at 190ºC for 24h. Equilibrium moisture content decreased more than 50% (at 35% relative humidity) reaching a maximum of 61% reduction. At higher air relative humidity the reduction was smaller, 49% and 38% at the most for 65% and 85% relative humidity. Dimensional stability (ASE) increased with maximum values of 88% and 96% in radial and tangential direction, respectively. The improvement was higher for lower relative humidity. There was a reduction on mechanical resistance with heat treatment especially for bending strength that decreased about 20% for 3% mass loss, reaching 60% for mass losses higher than 10%. MOE decreased with heat treatment the reduction was under 10% until 8% mass loss. The contact angle increased until 5% mass loss, decreasing slightly afterwards. Heat treatment was shown to be a useful method to improve the technological quality of eucalypt wood as regards dimensional stability allowing it to compete with higher cost woods for some applications.
- Pine wood modification by heat treatment in airPublication . Esteves, BrunoMaritime pine (Pinus pinaster) wood has low dimensional stability and durability. Heat treatment was made in an oven using hot air during 2 to 24 h and at 170-200 ºC. A comparison was made against steam heat treatment. The equilibrium moisture content and the dimensional stability (ASE) in radial and tangential directions were evaluated at 35%, 65% and 85% relative humidity. MOE, bending strength and wettability were also determined. At the same mass loss improvements of equilibrium moisture content and dimensional stability were higher for oven heat treatment but the same happened for mechanical strength degradation. A 50% decrease in hemicellulose content led to a similar decrease in bending strength.
- Heat induced colour changes of pine (Pinus pinaster) and eucalypt (Eucalyptus globulus) woodPublication . Esteves, BrunoHeat treatment of Pinus pinaster and Eucalyptus globulus wood was made by hot air in an oven during 2 to 24 h at 170-200 ºC and by steam in an autoclave during 2 to 12 h at 190- 210 ºC. The colour parameters L*, a* and b* were determined by the CIELAB method on radial, tangential and transverse sections for untreated and treated wood, and their variation with the treatment (ΔL*, Δa* and Δb*) were calculated in percent. In the untreated woods, for eucalypt wood lightness (L*) varied between 54.1- 63.8% with a* between 7.4-8.5 and b* 15.7-19.9, and for pine wood L* varied between 67.3-76.1%, a* between 6.9 -7.6 and b* 16.3 -24.1. With the heat treatment wood became darker, more for oven treatment (ΔL* about 50% for 4% mass loss), and at the same treatment conditions more for eucalypt wood. In general the contribution of the red colour (a*) and yellow (b*) decreased with the heat treatment. The transverse section darkened less in the two species and for both treatments, with small differences between radial and tangential sections. Lightness decrease was related to chemical changes, with good correlations with glucose (R2= 0.96), hemicelluloses (R2 = 0.92) and lignin (R2 = 0.86). As regards colour, the heat treatments showed an interesting potential to improve the wood quality for solid timber products from pine and eucalypt.
- Novos métodos de protecção da madeiraPublication . Esteves, Bruno; Pereira, HelenaEm Portugal, a preservação de madeiras para a Classe de risco 4 é feita através da impregnação com produtos de elevada toxicidade. O estudo de métodos alternativos de preservação é crítico para as empresas de preservação de madeira, alarmadas pelas limitações contínuas no uso dos produtos químicos. A modificação da madeira é um processo que melhora as propriedades como a resistência à biodegradação, a estabilidade dimensional, a resistência à radiação ultravioleta, entre outras, produzindo um material novo que no fim do ciclo de vida do produto não apresenta um perigo ambiental superior ao da madeira não tratada. Existem quatro tipos de processos: a modificação térmica, química, da superfície e a impregnação. A modificação térmica é aquela que tem mais sucesso sendo o processo Thermowood o mais utilizado. De entre os outros processos comerciais a acetilação (modificação química) e a furfurilação (modificação por impregnação) também se encontram bem implantados no mercado. De momento ainda nenhum processo de modificação superficial foi industrializado devido ao elevado custo. Neste artigo é feito um resumo dos principais processos de cada tipo de modificação apresentando as melhorias em relação à madeira não tratada, as vantagens e desvantagens de cada processo e a evolução em termos comerciais.
- Wood modification by heat treatment: a reviewPublication . Esteves, BrunoWood heat treatment has increased significantly in the last few years and is still growing as an industrial process to improve some wood properties. The first studies on heat treatment investigated mainly equilibrium mois-ture, dimensional stability, durability and mechanical properties. Mass loss, wettability, wood color, and chemical transformations have been subsequently extensively studied, while recent works focus on quality control, modeling, and study the reasons for the improvements. This review explains the recent interest on the heat treatment of wood and synthesizes the major publications on this subject on wood properties, chemical changes, wood uses, and quality control.