STUDIES ON STRUCTURE AND PROPERTIES OF NY LON 6 POLYAMIDE-ELASTOMER ALLOYS .2. MECHANICAL-PROPERTIES AND FRACTURE MECHANISM OF NYLON 6/POLYAMIDE-ELASTOMER ALLOYS/

Mechanical properties of nylon 6 and its alloys prepored from three ki nds of polyamide thermoelastomers have been studied. The elastic modul us and yield strength deacreased with an increae in the content of the rmoelastomers that caused an increase of the diameter of dispersed ela stomers and decrease of the degree of crystallinity. Nylon 6 showed lo w impact strength values in the temperature range from -18 to 45 degre es C. Whereas the alloys showed high impact strength of values which i ncreased with increasing temperature. SEM observations of the fracture surfaces and deformed regions beneath the fracture surfaces revealed that the fracture process of nylon 6 was brittle which was originated from plastic constraint at the notch tip. The fracture of alloys at 23 degrees C was also caused by plastic constraint at the notch tip. How ever, the plastic deformation zone at the notch tip was composed of ma ny voids and partially elongated fibrils, and this absorbed impact ene rgy. The fracture of alloys at 45 degrees C occurred in a ductile mann er in which there were many deformed voids and plastically elongated f ibrils within the plastic deformation zone. The plastic deformation wa s enhnaced by the transition of the stress state from plane strain to plane stress, The final fracture occurred from the notch tip connectin g voids in the plastic deformation zone.