Effects of Organic Sulfur and Phosphor Compounds Used as Antioxidants on the Thermal Behavior of Nitrocellulose and its Decomposition Mechanism

The effects of 3‐dodecylsulfanyl‐propionic acid 3‐(3‐dodecylsulfanyl‐propionyloxy)‐2,2‐bis‐(3‐dodecylsulfanyl‐propionyl‐oxymethyl)‐propyl ester (SO), 3,9‐bis‐octadecyloxy‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro5,5]undecane (POf), and 3,9‐bis‐(2,6‐di‐tert‐butyl‐4‐methyl‐phenoxy)‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro5,5]undecane (POp), which are used as antioxidants for polymers, on the degradation of nitrocellulose (NC) were investigated under isothermal storage conditions at 393 K with a microcalorimeter. The result indicated that SO/NC and POf/NC accelerated the heat release when compared with NC without an antioxidant, whereas the heat release behavior of NC/POp was similar to that of NC without an antioxidant. In the case of SO/NC and POf/NC, the heat release was observed in the presence of O₂, whereas it was not observed in a N₂ atmosphere. The SO content in SO/NC and PO content in POf/NC increased with the storage time. According to this behavior, it can be explained that sulfuric acid or phosphoric acid, which originates from SO or POf, accelerates the autoxidation of NC.