LIMA, D. R. Avaliação do desempenho anticorrosivo do revestimento de polibenzoxazina sintetizada a partir do líquido da castanha de caju. 2017. 44 f. Dissertação (Mestrado em Ciência de Materiais)-Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Hohana Sanders (hohanasanders@hotmail.com) on 2017-09-19T17:42:48Z No. of bitstreams: 1 2017_dis_drlima.pdf: 1177358 bytes, checksum: a6d5228462e2c5a3c6b66ec110abc6e6 (MD5) / Approved for entry into archive by Marlene Sousa (mmarlene@ufc.br) on 2017-09-25T17:47:55Z (GMT) No. of bitstreams: 1 2017_dis_drlima.pdf: 1177358 bytes, checksum: a6d5228462e2c5a3c6b66ec110abc6e6 (MD5) / Made available in DSpace on 2017-09-25T17:47:55Z (GMT). No. of bitstreams: 1 2017_dis_drlima.pdf: 1177358 bytes, checksum: a6d5228462e2c5a3c6b66ec110abc6e6 (MD5) Previous issue date: 2017-07-21 / The aim of this work was to evaluate the benzoxazine polymer, synthesized from the Cashew Nut Liquid (LCC) cardanol, as a coating for corrosion protection of AISI 1010 carbon steel. The physical properties of the synthesized polymer were characterized using Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and degree of crosslinking based on ASTM D2765. Polymeric film was prepared by brushing the benzoxazine resin on the steel surface, followed by curing at 200 °C, and its adhesion to the steel surface was evaluated by the grid cutting method according to ABNT NBR 11003. Corrosion tests consisted of exposure to saturated moisture and saline fog, and immersion in 0.6 mol L-1 NaCl solution, with the monitoring of the degradation of the coating accompanied by monitoring the open circuit potential and electrochemical impedance spectroscopy. From the thermal characterization and analysis of the swelling of the cured polymer film, it was observed that the film cured at 200 °C for 2 h had properties applicable to the use as coating since it presented 98% crosslinking with excellent thermal stability and approximately 55 μm of thickness. In the electrochemical tests the presence of the plasticizer in the benzoxazine polymer matrix influenced the coating efficiency. When compared to the concentrations of 5% and 10% of the plasticizer in the electrochemical tests, the concentration of 10% of the plasticizer was more protective against corrosion compared to 5%. These results suggest that benzoxazines synthesized from cardanol from Cashew Nut Liquid (LCC) can be used as an alternative coating for corrosion protection on AISI 1010 carbon steel surfaces. / Este trabalho teve por objetivo avaliar o polímero benzoxazina, sintetizado a partir do cardanol proveniente do Líquido da Castanha de Caju (LCC), como revestimento para a proteção à corrosão do aço carbono AISI 1010. As propriedades físicas do polímero sintetizado foram caracterizadas usando as técnicas de Calorimetria Exploratória Diferencial (DSC), Análise Termogravimétrica (TGA) e grau de reticulação baseado na norma ASTM D2765. O filme polimérico foi preparado pelo pincelamento da resina de benzoxazina na superfície do aço, seguido de cura a 200 °C, sendo que sua aderência à superfície do aço foi avaliada pelo método do corte em grade segundo a norma ABNT NBR 11003. Os testes de corrosão consistiram de exposição à umidade saturada, à névoa salina e imersão em solução de NaCl 0,6 mol L-1, sendo que o monitoramento da degradação do revestimento foi acompanhado por monitoramento do potencial de circuito aberto e espectroscopia de impedância eletroquímica. A partir da caracterização térmica e da análise do intumescimento do filme polimérico curado, verificou-se que o filme curado a 200°C por 2 h apresentou propriedades aplicáveis ao uso como revestimento, pois apresentou 98 % de reticulação com excelente estabilidade térmica e espessura em torno de 55 µm. Nos ensaios eletroquímicos a presença do plastificante na matriz polimérica das benzoxazinas influenciou a eficiência do revestimento. Quando comparadas as concentrações de 5 % e 10 % do plastificante nos ensaios eletroquímicos, a concentração de 10 % do plastificante mostrou-se mais protetora contra corrosão em comparação à 5 %. Estes resultados sugerem que benzoxazinas sintetizadas a partir do cardanol proveniente do Líquido da Castanha de Caju (LCC) podem ser utilizadas como um revestimento alternativo para proteção contra corrosão em superfícies de aço carbono AISI 1010.

Although, several researches on synthesis and characterization of benzoxazines and polybenzoxazines have appeared in the literature, detailed studies on thermal characterization are still limited. In this study, polymerization and thermal degradation mechanisms of benzoxazines were investigated via direct pyrolysis mass spectrometry. Benzoxazine monomers prepared by reactions of phenol or bisphenol- A with aniline or methyl amine were analyzed to investigate the effects of the structures of phenyl and amine groups on both polymerization and thermal degradation behaviours. It has been proposed in the literature that polymerization of benzoxazines occurs by ring opening polymerization of oxazine ring / cleavage of O-CH2 bond of the oxazine ring and attack of n-CH2 group to phenol or bisphenol-A ring. However, the direct pyrolysis mass spectrometry analyses of polymerization and thermal degradation of benzoxazines pointed out that after the cleavage of O-CH2 bond of the oxazine ring, polymerization proceeded through opposing pathways. Strong evidences confirming coupling of (CH3)NCH2 or (C6H5)NCH2 groups yielding dimers involving diamine linkages were detected. Polymerization of the dimer by the reactions with the corresponding monomers was proposed. In case of benzoxazines based on bisphenol-A, the results indicated polymerization of the dimer ii by coupling of both of the oxazine rings. On the other hand, polymerization of the dimer through the ethylene units (vinyl polymerization) in case of benzoxazine monomer based on phenol and methyl amine was also noted. For polybenzoxazines based on aniline another polymerization pathway involved attack of radicals generated by cleavage of the oxazine ring to aniline ring. Multi-step thermal decomposition was observed for all the polybenzoxazines under investigation confirming the presence of units with different structures and stabilities.