85 documents found, page 1 of 9
Quality Education for All: A Fuzzy Set Analysis of Sustainable Development Goal...
Luísa Carvalho; Dora Almeida; Ana Loures; Paulo Ferreira; Fernando Rebola; Carvalho, Luisa; Almeida, Dora; et al.The relationship between education and societal development is unquestionable. Education contributes to achieving both societies’ and individuals’ social and economic goals. Quality education is recognized as one of the Sustainable Development Goals (SDGs), which, jointly with other behaviors and attitudes, could impact the development of societies in other fields like health and well-being, cultural preservati...
Life Cycle Analysis of a Particleboard Based on Cardoon and Starch/Chitosan
António A. Martins; Teresa M. Mata; Clara Freitas; G. V. Silva; Sandra Monteiro; Jorge Manuel Santos Silva Martins; Luísa Carvalho; Luis Manuel SilvaThis work analyzes the life cycle environmental impacts of producing a particleboard based on cardoon fibers and a starch/chitosan adhesive from a cradle-to-gate perspective, considering the following life cycle steps: raw material production, adhesive preparation (component mixing and heating), cardoon fiber preparation (crushing and sieving), adhesive and fiber mixing, hot-pressing and final processing. The f...
Multi-Performance Characterization of a Modular Wooden House
J.M.P.Q. Delgado; Ana Mafalda Matos; Ana Sofia Guimarães; Eva Barreira; Luísa Carvalho; Jorge Manuel Santos Silva Martins; R.M.S.F. Almeida; N. FerreiraAlthough not a new concept, modular construction has been the target of increasing interest and investment in recent years. Modular wood construction systems have economic and environmental advantages, as wood is a natural and locally available raw material with interesting thermal properties. In this context, the BlueWoodenHouse Project, a closed cooperation project between academy and industry, aims to improv...
Classification of amino resins and formaldehyde near infrared spectra using K-n...
Miguel Gonçalves; N. T. Paiva; J. M. Ferra; Jorge Martins; Fernão D. Magalhães; Luísa CarvalhoAmino resins are synthetic adhesives that can be divided into three major types: urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF), or melamine-formaldehyde (MF). When less than 5% of melamine is added to a UF resin, the resin is called a melamine-fortified UF (mUF) resin. The extensive application of these resins in wood-based products is due to their many advantages: ease of use, strong bonding, resist...
Low density wood particleboards bonded with starch foam-study of production pro...
Sandra Monteiro; Jorge Martins; Fernão D. Magalhães; Luísa CarvalhoIt has been shown that wood particleboards bonded with sour cassava starch can display low density combined with good physico-mechanical performance, thanks to starch being able to produce a strong foam that fills the interparticular space. Here we optimize the pressing conditions for the production of these panels. The procedure involved hot-plate pressing in two stages: (1) lowering the top platen to a specif...
Improvement of storage stability of UF resins by adding caprolactam
P. Pereira; M. Almeida; J. Pereira; N. T. Paiva; J. M. Ferra; Jorge Martins; Luísa Carvalho; Fernão D. MagalhãesDuring storage, the structure of urea-formaldehyde (UF) resins suffers modifications due to reactions between monomers, oligomers, polymer and free formaldehyde, leading to increase in viscosity and decrease in pH. Eventually, viscosity reaches a value that renders the resin unusable, and it must be disposed off. This aging process is accelerated if storage temperature increases. The aim of this work is to obta...
Chemical composition of melamine-urea-formaldehyde (MUF) resins assessed by nea...
Miguel Gonçalves; N.T. Paiva; J. M. Ferra; Jorge Martins; Fernão D. Magalhães; Luísa CarvalhoMelamine-urea-formaldehyde (MUF) resins are commonly used in the production of wood-based panels. The composition of the resin influences many properties of the final product. In industrial production, some properties, such as viscosity, pH, solid content, or molar ratio, are assessed after resin production in order to evaluate if they are within the desired parameters. These properties are useful for quality c...
Impact of the Synthesis Procedure on Urea-Formaldehyde Resins Prepared by Alkal...
Carolina Gonçalves; João Pereira; Nádia Paiva; João Ferra; Jorge Martins; Fernão D. Magalhães; Ana Barros Timmons; Luísa CarvalhoIn this work, two synthesis procedures for the preparation of urea-formaldehyde (UF) resins, based on the alkaline-acid process, are studied in order to better understand the chemical reactions involved. For that purpose, the number of urea loads and the methyolation temperature were varied. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatogra...
Effect of peroxide oxidation on the expansion of potato starch foam
Joana V. Barbosa; Jorge Martins; Luísa Carvalho; Margarida M. S. M. Bastos; Fernão D. MagalhãesStarch-based foams are drawing increasing interest as bio-sourced alternatives to petroleum-based products when a low-density or air-filled cell structure combined with reasonable mechanical resistance is required. The chemical modification of starch, mainly via oxidation, can improve its expansion capability and, thus, reduce the density of the resulting foam. This study was done to investigate how the oxidati...
Introducing Flexibility in Urea-Formaldehyde Resins: Copolymerization with Poly...
Ana Antunes; Maria Rêgo; Nádia Paiva; João Ferra; Jorge Martins; Luísa Carvalho; Ana Barros Timmons; Fernão D. MagalhãesAdhesives obtained by copolymerizing urea, formaldehyde, and difunctional polyetheramine with different molecular weights (230, 600, 900, and 2000 gmol(-1)) are presented as a more resilient alternative to conventional urea-formaldehyde resins. Urea and polyetheramine contents were varied and the resulting resins characterized by FTIR, C-13-NMR, and TGA. These resins were used for production of agglomerated cor...