Enthalpies of Formation for a Selection of Newer and Conventional Stabilizers and Reaction Enthalpies for their Stabilization Action in Nitrocellulose

Computer simulation method as molecular dynamics (MD) and quantum mechanics (QM) can be used to determine mechanical and thermal properties of composite materials based on their chemical composition and crystal structure with acceptable accuracy. In the current study we used quantum mechanics calculations based on the density functional theory (DFT) to understand and improve the chemical stability of composite materials. The stabilization of nitrocellulose (NC) is based on the chemical bonding of the split-off NO and NO2 from the nitrate ester groups of the NC and nitrate ester plasticizers such as nitroglycerin, by stabilizers, e.g., diphenylamine (DPA). As the decomposition and /or reaction products of conventional stabilizers are suspected of being harmful to environment and human health, the focus of current research is on finding new, environmentally friendly stabilizers. We have calculated the standard enthalpies of formation of the conventional stabilizers DPA, AK II (Akardite) and EC (ethyl centralite or Centralite I), and of the so-called ’green’ stabilizers Stab-5 (Di-(2,6-dimethoxyphenol) ethylene glycol ether) from FOI, Sweden and Curcumin ((1E,6E)-1,7-Bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione). Both have methoxy-activated aromatic rings, facilitating the typical stabilizer reaction with NO2. Moreover, the enthalpies of reaction of the corresponding nitration reactions were determined. Here higher level of theory has been applied (DFT functional ‘ωB97X-D’ and basis set ‘aug-cc-pvtz’) together with a dielectric continuum around the molecule and allowing dispersion interactions. From these values, conclusions can be drawn in comparison about the stabilization action of these substances in nitrocellulose. All QM-calculations were performed with program suite Gaussian16 Rev. C.1.1 from company GaussianTM Inc.