Urea formaldehyde (UF) resins are widely used as adhesives for wood-based composites. These thermosetting polymers have advantages of relative low price, fast curing speed, and relative good bonding performance. However, UF resin bonded composites are designed for interior applications due to its weak water resistance. Moreover, traditional prevalent ways for recycling wood-based composites face problems caused by UF resins. In this project, the reuse of cured UF resins was systematically studied. The verification and characterization of crystalline structures in cured UF resins were conducted. The results showed that the crystalline regions were accounted for nearly 14.48% in a typical 1.2 formaldehyde to urea (F/U) molar ratio UF resin. The details of the resin crystalline regions, such as grain sizes and interplanar spacing (d-spacing), were characterized. The crystalline structures, nevertheless, did not affect the UF resin hydrothermal hydrolysis in this study. The reuse of cured UF resin was started with a hydrothermal hydrolysis. Under 140 °C and 2 h of hydrothermal process, 20 mL of 30 w.t. % formaldehyde water solution was able to depolymerize up to 1.7 g of cured UF resin. The hydrolyzed formaldehyde solutions were directly used as normal formaldehyde solutions for UF resin synthesis. The synthesized resin (named as UUF resin) contained about 6 w.t. % of cured UF resin and presented similar chemical structures and bonding performance as normal UF resins. Hybrid resins made of UUF resin and polymeric 4-4 diphenyl methane diisocyanate (pMDI) were prepared. The pMDI was found evenly dispersed in the hybrid resins by using acetone as its solvent. These hybrid resins resulted in faster curing and stronger bonding performance than pure UUF resins. Furthermore, the hybrid resin was used in a new bonding design, which used southern pine wood radial section features. This design generated finger joint like bonding interfaces by hot pressing two resin coated wood radial sections. The bonding strength and bond line stability were enhanced by this design.

The objective of this study was to investigate the effects of melamine and ether contents on the curing and performance properties of UF resins as binders for wood composites. Various UF and UMF resins were synthesized with three different synthesis procedures. These resins were examined by 13C NMR, rheometer, and other methods and evaluated as particleboard binders. Three-layer particleboards were prepared with the resins catalyzed with various catalysts and levels, applied in face and core layers. The board test results were compared. Only about half of added melamine had reacted with formaldehyde. UMF resins were found to be catalyzed with stronger catalysts at suitable levels depending on melamine levels and on which layer of particleboard the UMF resins are to be applied. Even catalyzed with a stronger catalyst, the curing rates of UMF resins were still slower, and storage stabilities were shorter than UF resins, but the pot lives were longer, and internal bond strength and water resistance were higher. Moreover, resins synthesized with procedures 2 and 3 showed obviously longer storage times, longer pot lives, and longer gel times, and the particleboards bonded with these resins showed significant improvements in internal bond strength and water absorption values but the formaldehyde contents increased. The increased formaldehyde content test values indicated that linear methylene-ether groups in UF resins decompose in the hot-pressing of boards to emit formaldehyde, most of which is not captured back into the UF resin matrix. Uron-type methylene-ether groups decompose in the hot-pressing of boards to participate in the curing process and enhance the bonding of boards, but it could also emit extra formaldehyde which may not be effectively captured by UF resins but more effectively by UMF resins if the amount of melamine is high enough because of the increased reactive capacities of melamine. The results of this research offered a new hypothesis that the linear methyleneether bonds in UF resins might be a major contributor of the high free formaldehyde contents of particleboards. Decreasing the linear methylene-ether groups contents might effectively bring down the formaldehyde content of boards.

Submitted by Ana Laura Soler Cunha Buzo (analaurasolercunha@gmail.com) on 2018-09-28T22:21:33Z No. of bitstreams: 1 DISSERTAÇÃO FINAL .pdf: 3047917 bytes, checksum: 4b9d9190322307f4e23c7de4f21936e9 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-10-01T13:05:23Z (GMT) No. of bitstreams: 1 buzo_alsc_me_ilha.pdf: 3047917 bytes, checksum: 4b9d9190322307f4e23c7de4f21936e9 (MD5) / Made available in DSpace on 2018-10-01T13:05:23Z (GMT). No. of bitstreams: 1 buzo_alsc_me_ilha.pdf: 3047917 bytes, checksum: 4b9d9190322307f4e23c7de4f21936e9 (MD5) Previous issue date: 2018-07-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O desenvolvimento de estudos para produção de derivados de madeira tem representado uma real alternativa para contribuir as políticas de sustentabilidade, principalmente de espécies arbóreas nativas. Nesse contexto, o reaproveitamento de resíduos lignocelulósicos tem contribuído como uma alternativa para a produção industrial de painéis de madeira. Dentro desse contexto este trabalho se constitui do estudo para produção e avaliação de painéis aglomerados, empregando-se partículas de bagaço de cana-de-açúcar (Saccharum officinarum) e partículas de madeira de pinus (Pinus taeda; Pinus elliottii) e utilizando-se dois tipos de aglutinantes, o Poliuretano derivado do óleo de mamona (PU-M) e a Resina Ureia-formaldeído (UF). Para produção dos painéis foram propostos diferentes tratamentos com variações entre as proporções de massas das partículas, densidade nominal dos painéis de 0,80 g/cm3 e pressão de prensagem de 50 kgf/cm2 durante 10 min. As misturas de partículas foram utilizadas com 10% de umidade para o adesivo PU-M e 3% de umidade para a resina UF ambos com um conteúdo de 10% em relação à massa seca das partículas. Para prensagem dos painéis com PU-M empregou-se 100 ºC e para os painéis com UF 130 ºC. Os painéis foram submetidos a ensaios para avaliação das propriedades físicas (densidade, umidade e inchamento) e mecânicas (módulo de elasticidade, módulo de ruptura à flexão e tração perpendicular) de acordo com a ABNT NBR 14810-1 e 2 (2013). Os resultados obtidos evidenciaram ser possível a utilização das partículas provenientes do bagaço de cana e de pinus para a produção de painéis aglomerados de alta densidade. Verificou-se que os painéis produzidos com o poliuretano apresentaram maior eficiência e suas propriedades físicas e mecânicas encontram-se compatíveis com os requisitos da Norma Brasileira para painéis do tipo P6 - Painéis estruturais para uso em condições severas de carga, em condições secas. Entretanto, verificou-se que os painéis produzidos com UF podem ser classificados como painéis do Tipo P2 - Painéis não estruturais para uso em condições secas. / The development of studies for the production of wood derivatives has represented a real alternative to improve sustainability policies, mainly of native tree species. In this context, the reuse of lignocellulosic waste has contributed as an alternative to the industrial production of wood panels. This way, this work aims to produce and evaluate chipboards using particles of sugarcane bagasse (Saccharum officinarum) and particles of pine wood (Pinus taeda; Pinus elliottii) and using two types of binders, the Polyurethane derived from castor oil (PU-Castor) and Urea formaldehyde resin (UF). Different treatments were proposed for the production of boards with variations between the particle mass ratios, panels’ nominal density of 0.80 g/cm3 and pressing pressure of 50 kgf/cm2 for 10 minutes. Particle mixtures were used at 10% moisture for the PU-Castor adhesive and 3% moisture for the UF resin both with a content of 10% relative to the dry mass of the particles. For the pressing of panels with PU-Castor was used 100 °C and of panels with UF was used 130 °C. The boards were submitted to tests to evaluate the physical properties (density, moisture and swelling after 24 hours) and mechanical (modulus of elasticity, modulus of resistance to bending and perpendicular traction) according to the ABNT NBR 14810-1 and 2 (2013). The results showed that it is possible to use particles from sugarcane bagasse and pine wood for high density chipboards production. It was found that the boards produced with polyurethane presented higher efficiency and their physical and mechanical properties are compatible with the requirements of Brazilian Standard Regulations for P6 boards (Structural boards for use under severe load conditions for dry conditions use). However, it has been found that panels made with UF can be classified as type P2 panels – Non-structural boards for dry conditions use. / CAPES - DS

Orientador: Sérgio Augusto Mello da Silva / Resumo: O desenvolvimento de estudos para produção de derivados de madeira tem representado uma real alternativa para contribuir as políticas de sustentabilidade, principalmente de espécies arbóreas nativas. Nesse contexto, o reaproveitamento de resíduos lignocelulósicos tem contribuído como uma alternativa para a produção industrial de painéis de madeira. Dentro desse contexto este trabalho se constitui do estudo para produção e avaliação de painéis aglomerados, empregando-se partículas de bagaço de cana-de-açúcar (Saccharum officinarum) e partículas de madeira de pinus (Pinus taeda; Pinus elliottii) e utilizando-se dois tipos de aglutinantes, o Poliuretano derivado do óleo de mamona (PU-M) e a Resina Ureia-formaldeído (UF). Para produção dos painéis foram propostos diferentes tratamentos com variações entre as proporções de massas das partículas, densidade nominal dos painéis de 0,80 g/cm3 e pressão de prensagem de 50 kgf/cm2 durante 10 min. As misturas de partículas foram utilizadas com 10% de umidade para o adesivo PU-M e 3% de umidade para a resina UF ambos com um conteúdo de 10% em relação à massa seca das partículas. Para prensagem dos painéis com PU-M empregou-se 100 ºC e para os painéis com UF 130 ºC. Os painéis foram submetidos a ensaios para avaliação das propriedades físicas (densidade, umidade e inchamento) e mecânicas (módulo de elasticidade, módulo de ruptura à flexão e tração perpendicular) de acordo com a ABNT NBR 14810-1 e 2 (2013). Os resultados obtidos evidenciara... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The development of studies for the production of wood derivatives has represented a real alternative to improve sustainability policies, mainly of native tree species. In this context, the reuse of lignocellulosic waste has contributed as an alternative to the industrial production of wood panels. This way, this work aims to produce and evaluate chipboards using particles of sugarcane bagasse (Saccharum officinarum) and particles of pine wood (Pinus taeda; Pinus elliottii) and using two types of binders, the Polyurethane derived from castor oil (PU-Castor) and Urea formaldehyde resin (UF). Different treatments were proposed for the production of boards with variations between the particle mass ratios, panels’ nominal density of 0.80 g/cm3 and pressing pressure of 50 kgf/cm2 for 10 minutes. Particle mixtures were used at 10% moisture for the PU-Castor adhesive and 3% moisture for the UF resin both with a content of 10% relative to the dry mass of the particles. For the pressing of panels with PU-Castor was used 100 °C and of panels with UF was used 130 °C. The boards were submitted to tests to evaluate the physical properties (density, moisture and swelling after 24 hours) and mechanical (modulus of elasticity, modulus of resistance to bending and perpendicular traction) according to the ABNT NBR 14810-1 and 2 (2013). The results showed that it is possible to use particles from sugarcane bagasse and pine wood for high density chipboards production. It was found that the boards... (Complete abstract click electronic access below) / Mestre

No description available.