Morphology and mechanical properties of injection molded articles with weld-lines

Abstract

The effect of weld-lines on the morphology and mechanical properties of injection molded articles made of neat poly(butylene terephthalate) (PBT) and glass fiber-reinforced PET was investigated. The weld-line was introduced to a molded article by using a rectangularly shaped insert inside a mold cavity, and tensile specimens were prepared at various positions through the entire molded article. The weld-line position was further checked by a short-shot experiment. Although tile maximum tensile stress for specimens of neat PET with a weld-line is almost the same as that without a weld-line, the maximum tensile stress and the elongation at break for fiber-reinforced PET with a weld-line were found to be about half of those without the weld-line. This is attributed to the fact that the fibers near the weld-lines are oriented parallel to the meld-line direction (or perpendicular to the tensile force direction) due to stretching now. Finally, we compared experimental results of flow pattern and fiber orientations with numerical simulations. We found that the predictions of flow fronts and fiber orientations are in good agreement with experimental results.