Study of the Consumption of the Curing Agent on the Liner Surface by Infrared Spectroscopy in Reflection Mode

Authors

  • Rodrigo Macêdo Rios Departamento de Ciência e Tecnologia Aeroespacial – Instituto Tecnológico de Aeronáutica – Divisão de Ciências Fundamentais – São José dos Campos/SP – Brazil. https://orcid.org/0009-0008-0059-9478
  • Milton Faria Diniz Departamento de Ciência e Tecnologia Aeroespacial – Instituto de Aeronáutica e Espaço – Divisão de Propulsão – São José dos Campos/SP – Brazil. https://orcid.org/0000-0003-0246-0660
  • Régis da Silva Santos Departamento de Ciência e Tecnologia Aeroespacial – Instituto de Aeronáutica e Espaço – Divisão de Produção de Motores – São José dos Campos/SP – Brazil. https://orcid.org/0009-0009-0209-2512
  • Natália Beck Sanches Centro de Tecnologia da Informação Renato Archer – Coordenação de Laboratórios Abertos e Parque Tecnológico – Campinas/SP – Brazil. https://orcid.org/0000-0002-3545-119X
  • Juliano Ribeiro Aguiar Pinto Departamento de Ciência e Tecnologia Aeroespacial – Instituto de Aeronáutica e Espaço – Divisão de Produção de Motores – São José dos Campos/SP – Brazil. https://orcid.org/0000-0002-5510-0901
  • Rita de Cássia Lazzarini Dutra Departamento de Ciência e Tecnologia Aeroespacial – Instituto Tecnológico de Aeronáutica – Divisão de Ciências Fundamentais – São José dos Campos/SP – Brazil. https://orcid.org/0000-0001-9958-1279

DOI:

https://doi.org/10.1590/jatm.v18.1424

Keywords:

Adhesives, Curing, Infrared spectroscopy, Isocyanates, Surfaces

Abstract

Monitoring the reaction between the isocyanate group (NCO) of the curing agent 2,4-toluene diisocyanate and the hydroxyl group (OH) of hydroxyl-terminated polybutadiene is important for the rocket engine loading process, since the reduction of NCO content on the adhesive surface (liner) directly affects adhesion to the propellant. Traditionally, the tack point, which represents the optimal time window for rocket motor loading, is determined based on the operator’s tactile perception. Viscosimetry is employed to monitor adhesive curing and subsequently assess tack; however, as this method evaluates the reaction within the bulk material, adhesion control remains predominantly empirical when chemical reference parameters are preferred. This study proposes a methodology based on infrared spectroscopy (IR) in universal attenuated total reflection mode, evaluating four stoichiometric ratios R(NCO/OH): R = 1.00 and, with excess NCO, R = 1.05, 1.10, and 1.15. The ratio R = 1.05 showed the best performance, with a methodological error of 4%. The main contribution of this work is a fast and precise IR surface analysis that enhances process control during solid rocket motor loading.


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Published

2026-02-09

Issue

Vol. 18 (2026)

Section

Editorial

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Copyright (c) 2026 Rodrigo Macêdo Rios, Milton Faria Diniz, Régis da Silva Santos, Natália Beck Sanches, Juliano Ribeiro Aguiar Pinto, Rita de Cássia Lazzarini Dutra

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