Effect of certain additives and the ambient medium on the static and fatigue strengths of polyamides

The change in the static strength of polycaprolactam during heat treatment has been investigated in relation to the type of additive and the ambient medium, and the change in dynamic strength in relation to the method of introducing the stabilizer. It has been observed that there is a slowdown in the thermal oxidation and loss of strength of polyamides exposed to heat in a medium containing stabilizer vapors and of polycaprolactam heat-treated after being coated with lacquer containing a thermostabilizer.On the basis of the experimental material it is suggested that the loss of strength of polyamides associated with thermal oxidation is due principally not to a reduction in molecular weight or crosslinking but to stress concentrations and microdefects associated with rupture of the molecular chain. An effective method of increasing the dynamic strength of polyamides has been found.Mekhanika Polimerov, Vol. 2, No. 1; pp. 60–66, 1966