In the Brazilian Aerospace Program, even though all developed rocket motors are manufactured in the same plant of the Department of Aerospace Science and Technology, differences are observed in the magnitude of the masses applied in each motor. Thus, depending on the volume of the combustion chamber, it is common for the casting to carry out multi-batch processes when a required mass of solid propellant is greater than the maximum capacity of the reactor. In this context, the studies that systematically evaluate multi-batch processes on an industrial scale of composite propellants based on polyurethanes obtained from HTPB are incipient. Furthermore, each batch preparation of the casting process for large motors is carried out on different days, so that each of these has a different storage time until the day of the effective casting. As a result, this wait can generate changes in the properties of the propellant grain as a whole, which can modify the motor's performance. Thusly, through the analysis of data of multi-batch processes, the present study evaluated the influence of the storage time in the preparation of the propellant and on the final properties of the grain. It was concluded that the grain becomes softer with a reduction in its hardness, greater elongation at break, and less modulus for batches with longer storage times before casting.

No abstract

The solid composite propellant is a viscoelastic material that retains the treatment received during its all-useful life. As a result, its manufacturing conditions induce differences in its final mechanical properties. The present study aims to evaluate the influence of the type and size of the reactor and the effects of the heating interruption during curing on the final mechanical properties of the propellant. Thus, four production processes with identical propellant formulations were performed in four different reactors. One of them was vertical, while the others were horizontal reactors. The heating interruption during curing was performed in 10 samples, at different moments of the curing process and with different duration. The study determines that vertical reactors tend to produce propellants less rigid than those produced in the horizontal type. In addition, the bigger the reactor size, the less rigid the propellant becomes. Finally, the heating interruptions at the beginning of the curing process tend to be insignificant. However, when they occur in an advanced stage of the curing process, they tend to hinder the curing progress, being more significant for interruptions of medium duration.

RESUMO O presente estudo avaliou diferentes formulações de propelentes sólidos à base de PBLH/AP/Al modificados por dióis de cadeia curta, 1,4-butanodiol e 1,2-propanodiol, em diferentes concentrações mássicas, com intuito de obter propriedades mecânicas diferenciadas sem negligenciar os demais requisitos impostos, tais como processabilidade e propriedades balísticas, destas mesmas formulações. Neste sentido, desenvolveu-se uma metodologia de cálculo das formulações, onde o processamento das mesmas foi realizado em reator de pequeno porte. Com a intenção de avaliar a influência do teor mássico de plastificante empregado, também foi processada uma formulação, de maior teor de 1,4-butanodiol, com maior quantidade de plastificante. Para tanto, avaliou-se o perfil de viscosidade dinâmica pós-processamentos, a evolução da propriedade mecânica da dureza durante a cura e realizaram-se ensaios mecânicos de tração e dureza finais. Realizaram-se também ensaios de determinação de massa específica, Raio-X das amostras e bomba calorimétrica. Ficou evidente que formulações modificadas com 1,4-butanodiol são promissoras. Não obstante, não foi possível alcançar no presente estudo todos os requisitos esperados em um produto final para emprego imediato.