Effects of morphology on mechanical and tribological properties of polyamide/polyethylene blends

Tribological, mechanical, and morphological properties of polyamide 6/maleic anhydride grafted high density and low density polyethylene (MAH-g-HDPE, LDPE)-blends were investigated. MAH-g-PEs with various MAH ratios were prepared by mixing PEs/MAH/peroxide(1,3-bis(t-butylperoxyisopropyl)benzene) = 100/1.0/0.1 (by weight) in a twin screw extruder. The grafting ratios of MAH to HDPE and LDPE were controlled by the reaction temperature. 10 similar to 30 wt% MAH-g-HDPE and LDPE were blended with PA 6 at 240 degrees C and then injection molded into ASTM flexural and tensile test pieces. The morphological study of the blends was carried out by means of SEM and TEM. Tribological properties such as coefficient of friction and specific wear rate were measured by using a Pin-on-Disk type test apparatus at 28 degrees C. Introduction of MAH into HDPE and LDPE greatly decreased the PE particle size in PA 6 matrix. PA 6 showed a higher coefficient of friction and a higher frictional wear than HDPE. Although both the coefficient of friction and the frictional wear of HDPE tended to increase with MAH grafting ratio, those of PA 6/HDPE decreased with MAH grafting ratio and reached to those of HDPE. PA 6/LDPE blends showed the opposite tribological behavior with MAH grafting ratio to PA 6/HDPE blends, except for LDPE neat samples. The difference of these tribological properties seems to be due to the mechanical properties caused by dispersed particle size change of the blends for HDPE which affects the formation of films transferred onto the metal disk of blend polymers for LDPE.