| Abstract: | The effects of weld lines in injection moldings of nylon 6 and nylon 6 nanocomposite samples were investigated by comparing single‐end‐gated and double‐end‐gated tensile samples. The single‐gated samples have no weld line, whereas the double‐end‐gated configuration produces a weld line at the center of the gauge length. Nylon 6 shows little variation in tensile properties for samples with or without weld lines, remaining ductile and tough, even with weld lines present. However, nylon 6 nanocomposites containing organically modified montmorillonite (organoclay), produced by a melt blending technique, exhibits rigid and brittle behavior for both single (no weld line) and double‐end‐gated (with weld line) samples. The organoclay increases the tensile strength but reduces the strain‐to‐failure significantly in both cases. A modified L16 orthogonal array based on the Taguchi approach with three levels was designed to run injection‐molding experiments to allow production of a modest number of samples to identify the most important process factors. The results were analyzed using the statistical tools signal‐to‐noise (S/N) ratio and analysis of variance (ANOVA), in particular showing that the principal process factors for the double‐end‐gated nylon 6 nanocomposite samples are mold and melt temperatures. POLYM. ENG. SCI., 45:1606–1614, 2005. © 2005 Society of Plastics Engineers |
