Stabilization of Polyamides Against Thermal Oxidation

The patent literature contains very many indications of the possibility of stabilizing polyamides against thermal oxidation. However, the literature contains almost no research works discussing the mechanism of the action of antioxidants for polyamides. 

A number of survey works consider the action of inorganic [39-41], as well as organic [35, 42-44] additives to polyamides. 

In all these works a comparison was made of the mechanical properties of stabilized and unstabilized polyamide fibers, subjected to thermal oxidation. 

A large number of antioxidants of organic structure, of the type of amines and phenols, were investigated in [42, 43]. The additives were introduced by powdering the capron in the form of crumbs before spinning of the fiber, as well as into the fused caprolactam before polymerization. The antioxidants beloi ing to the amine class, such as N,N -di-/3 -naphthyl-p-phenylenediamine, N, N-phenylcyclohexyl-p-phenylenedi-amine, N,N -diphenyl-p-phenylenediamine, and phenyl-jS-naphthylamine, preserve the strength of the fiber by 70-95% when it is heated for 2 hr 

In the stabilization of polyhexamethylenesebacamide, aromatic amines also proved most effective DNPDA and phenyl-i3-naphthyl-amine (neozone D). 

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