Effect of melt temperature and skin‐core morphology on the mechanical performance of nylon 6

The crystalline texture and mechanical (tensile and flexural) properties of injection molded nylon 6 were evaluated to understand the influence of the melt temperature (Tmlt), one of the key‐processing variables. The mechanical properties are found to be sensitive to Tmlt only below ∼ 250°C. Rapid quenching of the surface produces a skin with lower crystallinity than the core, which cools more slowly; because of this difference in the rate of cooling, the crystalline component in the skin is rich in γ and that in the core is rich in α. The thickness of this skin decreases from about 1.25 mm to 0.75 mm as Tmlt increases from 225°C to 310°C. Higher tensile strength at yield, lower elongation at break and higher flexural strength were observed in specimens molded at lower Tmlt. These characteristics are associated with thicker and less ordered skin, and a lower crystallinity core. The role of the Tmlt, on microstructure and mechanical properties of injection molded nylon 6, the development of skin‐core morphology, and the role of the residual stresses in the core are discussed.