EFFECT OF HEAT AGEING ON MECHANICAL PROPERTIES OF POLYAMIDE 6(NYLON 6) & POLYAMIDE 12(NYLON 12)

Abstract

Polyamide 6 or Nylon 6(PA 6) and polyamide 12 or Nylon 12 (PA 12) are well known engineering semi-crystalline polar polymers characterized by the presence of amide linkage (-CONH-) in the repeating units of their chains. The glass transition temperature (Tg) of PA 6 and PA 12 is ~50 °C and ~37 °C respectively. PA 6 is widely used for gears and bearings, fittings in automobile industry for under hood parts and also as a material for power tools housings. PA 12 is mainly used for special applications in automobile industry like, to prepare fuel tank and oil-gasoline resistant pipes/tubes. When any polymer is used for a long period of time, it becomes aged. Heat aging process affects not only the material property but also decide the service life of polymer. Therefore study of heat aging properties of polymers is a fundamental topic both from academic and industrial view-point. In the present study, Injection molded specimens of PA 6 and PA 12 were heat-aged in an oven at a temperature ranging from below the glass transition temperature (Tg) of PA and above the Tg for a specific period ranging. The heat aging effects on PA 6 and PA 12 in terms of mechanical properties such as tensile modulus (E), tensile yield strength (σy), elongation at break (εb) and Izod impact strength were investigated under various conditions. Extensive literature survey revealed that, no such systematic aging studies for Nylon 6 and Nylon 12 are reported so far.