On the replacement of traditional stabilizers by guaiacol in environmentally safe nitrocellulose-based propellants

Rodrigo L. B. Rodrigues,Letivan G. Mendonça Filho,Ana Paula da Silva,Rogério Rosato,Fernando C. Peixoto,Tanos C. C. França,Maurício F. Lemos

doi:10.1007/s10098-022-02291-4

Abstract

In this work we investigated the possibility of substituting diphenylamine (DPA) by the natural product 2-methoxy phenol, known as guaiacol (CAS 90-05-1), as a stabilizer for nitrocellulose (NC)-based propellants. Stability evaluation, using heat flow calorimetry, revealed lower heat flows associated with our guaiacol-stabilized propellant samples when compared to those of propellants stabilized with the traditional stabilizers. Also, pressure vacuum stability tests showed that our propellant exhibited lower evolved gas volumes. Traditional tests, such as the German Test, and the Bergmann-Junk Test, scored a NO volume, after titration, of 0.87 ml (below the limit-value for acceptance, which is 2.0 ml), and the Storage Test, showed that our samples are stable and do not degrade until 3 days when submitted to a constant temperature of 100 °C. The homogeneity, stability and compatibility of our samples were evaluated through scanning electron microscopy, differential scanning calorimetry, and isothermal thermogravimetry. Ballistic parameters were estimated using a closed vessel along with computational codes developed by our research group, for comparison purposes. Finally, the high-performance liquid chromatography method allowed inferring the stabilizer consumption after artificial ageing of samples. This method also showed that the material met the corresponding stability criteria of AOP-48. Concluding, our results clearly indicate that guaiacol is an effective and efficient substitute for DPA as a propellant stabilizer for single-base NC-based propellants, making them more environmentally friendly.Graphical abstract

Highlights

Nitro esters, such as nitrocellulose (NC), have been extensively used as propellants due to some unique characteristics, such as their high energetic potential
In this work we investigated the possibility of substituting diphenylamine (DPA) by the natural product guaiacol, as a stabilizer for nitrocellulose (NC)-based propellants
Stability evaluation, using heat-flux calorimetry (HFC), revealed lower heat flows associated with our guaiacol-stabilized propellant samples when compared to those of propellants stabilized with the traditional stabilizers

Summary

Introduction

Nitro esters, such as nitrocellulose (NC), have been extensively used as propellants due to some unique characteristics, such as their high energetic potential. Over time, several catastrophic accidents resulting from the NC decomposition, have showed that the chemical stability is an important aspect to ensure a safe use and storage of propellants (de Klerk, 2015; Defanti et al, 2020). This NC degradation was identified as being intrinsic to the nitro esters, depending on temperature and time, and happens mainly due to denitration reactions based on the chemical detachment of –NO2 groups caused by thermal decomposition and hydrolysis reactions involving the residual moisture present in the propellant mass (Bohn, 2007). As these compounds are amines and secondary amides, the degradation process leads to the formation of R–N–N=O (where R is an alkyl radical), which are suspected of being carcinogenic (Lin, 1990)

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