Effects of moisture after injection on the mechanical properties of PA 6 and PA 66 materials

Polyamides are among the first engineering plastics which have a wide variety of usage in industrial applications. These materials are very sensitive to moisture which acts as a plasticiser. With the increasing of absorbed moisture, strength and stiffness reduces but toughness and elongation increases. Higher moisture levels improve the impact absorbtion ability and ductility. In this thesis, the effects of moisture absorbtion on mechanical properties of PA 6 and PA 66 materials were investigated using tensile test specimens which had the dimensions in accordance with ASTM D 618, which were prepared by using the injection molding method. The tensile test specimens were conditioned in 80 celcius degrees water with three different time periods. 10, 20 and 30 hours immersions were applied. After conditioning, specimens were isolated from the environment by the help of HDPE bags and tensile tests were conducted for every specimen at certain time periods. Stress ? strain curves were drawn for 10, 20, 30 hours test specimens and the results were compared with each other. It has been observed that after conditioning of PA 6 and PA 66 materials, the yielding and ultimate strength decreased; toughness, impact absorbtion ability and strain rates increased. The importance of production conditions of polyamide materials were realised with the help of tensile tests which consisted of same conditioned test specimens.Keywords: Polyamide, moisture content, mechanical properties