A Study of the Effect of Temperature, Moisture, and a Solution of Salts on the Properties of Polyamide 11. 1. Extension and Compression

Accelerated laboratory tests of tubes made of Polyamide 11 with three compositions for the action of elevated temperature, thermal cycles, relative humidity, and an aqueous solution of salts for 200–3000 h are conducted. To find out the effects of aging, the weight of the samples, ultimate strength, Young modulus, and tensile elongation as well as rigidity of the tubes upon compression are measured. A clearly pronounced decrease in the weight of the tubes is found under all the conditions of accelerated tests which is induced by the removal of monomer residues, antioxidants, and plasticizers from the bulk of the samples. A result of thermal and thermal-cycle action on the tubes turns out to be an increase in their strength and rigidity accompanied by a simultaneous decrease in tensile elongation. Exposure at increased relative humidity only partially compensates embrittlement of Polyamide 11 as a result of the plasticizing action of sorbed moisture. Out of all the studied modes of aging, only exposure of the tubes in a solution of salts induces plasticization under the action of water molecules, as a result of which mechanical indicators of the polymer unsubstantially change. The performed tests show high resistance of Polyamide 11 to accelerated aging.