No description available.

Dielectric monitoring and supporting techniques (differential Scanning calorimetry, infra-red spectrosoopy, viscometry, dynamic mechanical thermal analysis and light transmittance) were used to study the isothermal cure reaction of the CTBN rubber modified DGEBA resin/amine hardener blends. The neat system was also examined for the required knowledge of the matrix properties. The complexity of the cure kinetics was demonstrated by the use of a rapid technique for kinetic parameters evaluation. The utility of the dielectric cure monitoring is focused at the observation of evidence o phase separation, gelation and vitrification. The phase separatlon which the blends underwent during the cure was detected by the dielectric »monitoring through a permittivity increase at the low frequency response. The onset of the rapid viscosity increase leading to gelation was also indicated by the sharp decrease o the dielectric constant atlhigh frequencies. The frequency dependence of the times reach the dielectric loss peaks was used to predict successfully the vitrification times during the isothermal reactions o the blends. The in-situ nature o the technique and the basic understanding o the features appearing in the dielectric signal during the cure reaction provide the basis for the use of dielectric monitoring in the process of composite materials, manufacture.

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Submitted by José Eduardo Estevam da Silva (eduardoposmat@gmail.com) on 2018-04-15T21:56:51Z No. of bitstreams: 1 DISSERTAÇÃO VERSÃO FINAL.pdf: 4070557 bytes, checksum: fb263583bfb8f6573957500e76dce18a (MD5) / Approved for entry into archive by Minervina Teixeira Lopes null (vina_lopes@bauru.unesp.br) on 2018-04-16T19:34:27Z (GMT) No. of bitstreams: 1 silva_jee_me_bauru.pdf: 3974286 bytes, checksum: c0b61a56b4e52184bb3bdb58c2d99f52 (MD5) / Made available in DSpace on 2018-04-16T19:34:27Z (GMT). No. of bitstreams: 1 silva_jee_me_bauru.pdf: 3974286 bytes, checksum: c0b61a56b4e52184bb3bdb58c2d99f52 (MD5) Previous issue date: 2018-01-26 / O processo de fabricação de painéis MDF é muito dinâmico e a todo instante surgem novidades tecnológicas buscando não somente otimizar custos de processo, mas incrementar novas características ou melhorar a resistência mecânica e usinabilidade. As fibras de madeira de eucalipto e as resinas termofixas como a uréia-formaldeído desempenham papel importantíssimo no contexto industrial. Um grande número de pesquisas e estudos se direciona a aperfeiçoar os processos de fabricação por meio do aprimoramento da matéria-prima. Muitos materiais foram desenvolvidos e adicionados tanto as fibras como as resinas sendo muito comum a busca por melhorias na resistência mecânica nas chapas MDF. A resina MDI (metileno difenil diisocianato), por exemplo, possui muitas vantagens conhecidas como a isenção de emissão de formol e a alta resistência a água, porém, outras características relacionadas à interação química com a madeira são pouco estudadas. Nesse contexto tecnológico, o presente trabalho se dedicou ao uso das técnicas termoanalíticas TG/DTG-DTA e DSC para investigar e compreender melhor a interação química entre as fibras de madeira de eucalipto e as resinas sintéticas termofixas e por fim, sugerir melhorias ao processo produtivo buscando assim, reduzir custos de fabricação. Além das técnicas termogravimétricas, a espectroscopia vibracional de absorção na região infravermelho médio com transformada de Fourier também foi usada para auxiliar na proposta reacional de polimerização e principalmente na identificação da estrutura química dos produtos gerados. Investigou-se também o processo de polimerização térmica do monômero MDI bem como sua degradação térmica seguindo as recomendações do ICTAC. As curvas TG/DTG-DTA mostraram que a polimerização foi incompleta em todas as resinas indicando a necessidade de ajustes no processo. A proposta reacional para as resinas UF e MDI está de acordo com os dados das curvas TG e espectros de MIR. A partir da polimerização da resina MDI sugeriu-se a formação de carbodiimidas como produto final. Ao final da pesquisa, algumas melhorias foram propostas como o aumento da temperatura da prensa e a diminuição da concentração de resina visto que na situação atual, a polimerização é incompleta e deixa resíduos nas chapas MDF. Comprovou-se também que as chapas fora de especificação podem ser usadas como biomassa combustível nas caldeiras em substituição ao cavaco de eucalipto, pois liberam mais calor quando estão em combustão. / The process of manufacturing MDF panels is very dynamic and at every moment technological innovations are emerging, seeking not only to optimize process costs, but to increase new characteristics or improve mechanical strength and machinability. Eucalyptus wood fibers and thermoset resins such as urea-formaldehyde play a very important role in the industrial context. A great number of researches and studies are directed at perfecting the manufacturing processes through the improvement of the raw material. Many materials have been developed and added to both fibers and resins, and the search for improvements in mechanical strength in MDF sheets is very common. MDI resin (methylene diphenyl diisocyanate), for example, has many advantages known as formaldehyde emission exemption and high water resistance, but other characteristics related to the chemical interaction with wood are little studied. In this technological context, the present work was dedicated to the use of TG / DTG-DTA and DSC thermoanalytical techniques to investigate and better understand the chemical interaction between eucalyptus wood fibers and thermosetting synthetic resins and, finally, to suggest improvements to the production process thus seeking to reduce manufacturing costs. In addition to the thermogravimetric techniques, the vibrational absorption spectroscopy in the medium infrared region with Fourier transform was also used to aid in the polymerization reaction proposal and mainly in the identification of the chemical structure of the generated products. The thermal polymerization process of the MDI monomer as well as its thermal degradation following the recommendations of the ICTAC were also investigated. The TG / DTG-DTA curves showed that the polymerization was incomplete in all resins indicating the need for process adjustments. The reaction proposal for the UF and MDI resins is in agreement with the data of the TG curves and MIR spectra. From the polymerization of MDI resin the formation of carbodiimides was suggested as the final product. At the end of the research, some improvements were proposed, such as the increase in the temperature of the press and the decrease of the resin concentration, since in the current situation the polymerization is incomplete and leaves residues in the MDF sheets. It has also been proven that non-specification sheets can be used as biomass fuel in boilers instead of eucalyptus chips, as they release more heat when they are in combustion.

Sjöfarten använder sig i stor utsträckning av färg förstärkt med härdplaster. Dessa kan vara hälsovådliga utan rätt skyddsutrustning och det ställs krav på att alla som handhar härdplaster ska ha genomgått en utbildning och regelbundna spirometriundersökningar. Studenter från Sveriges två sjöfartshögskolor går idag ut på fartygsförlagd utbildning med olika grundkunskaper om härdplaster. Vissa har fått härdplastutbildning och andra har ännu inte hunnit få det. Denna studie har genom en serie kvalitativa intervjuer försökt att kartlägga effekterna av detta. Intervjuerna med studenter och matroser har visat att de studenter som hade fått härdplastutbildning också hade en mycket bättre förståelse för riskerna med härdplaster och för hur de kunde exponeras för faran. Studenterna utan utbildning förstod risken med det skadliga elementet men saknade kunskapen för att adekvat kunna skydda sig. Studien visar också att faktorer som påverkar användandet av personlig skyddsutrustning i stor utsträckning är kopplat till ålder, erfarenhet och den övriga besättningens attityd till riskerna. / The maritime world makes use of paint reinforced with thermosetting polymers. These may be harmful without the correct protective equipment and there are regulations stating that anyone working with it must be educated in the handling and risks associated with said paint as well as regularly undergo a spirometric test. Today students from the two Swedish maritime universities undertake their onboard studies under different conditions, some with the correct education and some without. This study has through a series of qualitative interviews tried to expose the effects. The interviews have shown that students with the correct education have a much better knowledge of the risks associated with thermosetting polymers and the different ways it might be exposed to them. The uneducated students were aware of the dangers but lacked the knowledge to adequately protect themselves. However, the study showed that this did not determine whether the students use personal protection as much as such factors as age, experience and the rest of the crew's attitude towards the risks.