216 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES
The next stage would be the formation of the nitroso compound:
(36b)
VI VIINext, various interactions between V, VI, VII and free radicals would occur.
As Kite [85] observed, aromatic nitro compounds inhibited the polymerization
of vinyl acetate more strongly than that of methyl methacrylate.
It is interesting to see, that C-nitroso- and N-nitroso compounds (e.g. nitroso-
acetanilide, N-nitrosoacylarylamines) catalyse polymerization reactions (Hey [86-88],
Blomquist, Johnson and Sykes [89]).
Hey suggested in 1947 the following plausible scheme for the action of N-nitroso-
acylarylamine :(37)This action is similar to that of benzoyl peroxide.
VULCANIZATION OF RUBBER WITH AROMATIC NITRO COMPOUNDSOstromyslensky [90] observed that rubber could be vulcanized in the absence
of sulphur or its compounds if small quantities of aromatic nitro compounds,
e.g. nitrobenzene, dinitro- or sym- trinitro-benzene, tetranitronaphthalene plus
certain oxidizing compounds, such as benzoyl peroxide, were added to it. The
resultant vulcanized rubber had mechanical properties not inferior to those of a
product vulcanized by sulphur alone, and when free from accelerators it exhibited a
greater resistance to ageing. Some metal oxides, such as PbO, CaO, BaO, promoted
vulcanization by nitro compounds. Urea played the role of an accelerator of
vulcanization. These observations have been confirmed in more recent studies by
other workers.
The action of m- dinitrobenzene chiefly as a vulcanizing agent, has been studied
by Wright [91] and Blake [92] who found that all the m- dinitrobenzene entered
into reaction with rubber when added in the proportion of 6%. Blake failed to
obtain hard rubber (“ebonite”) that way. A method for obtaining hard rubber
by using m- dinitrobenzene was, however, described by Wright [91]. Rubber vulcan-
ized by nitro compounds has the advantage of not corroding metals (Koshelev [93]).
The investigation of sulphurless vulcanizing agents, including the use of poly-
nitro derivatives of benzene, has been completed by Mark and his co-workers [94]).
The hypothesis has been advanced that during the vulcanization of natural
rubber by means of polynitro compounds, a partial reduction of polynitro- to
nitroso compounds takes place, the latter being known as vulcanizing agents.
In practice, the application of nitro compounds (e.g. m- or p- dinitrobenzene)