Comparative study of weld‐line strength for unfilled and glass‐filled thermoplastic polyamide‐6 materials

• Published in: Polymer engineering and science 2023-04, Vol.63 (4), p.1116-1125
• Main Authors: Jadhav, Ganesh, Gaval, Vivek
• Format: Article
• Language: English
• Subjects: Anisotropy; Comparative studies; Fiber orientation; Injection molding; injection molding method; Mechanical properties; Polyamide resins; Polyamides; polyamide‐6; Simulation methods; Tensile properties; Tensile strength; Tensile tests; Thermoplastic resins; Thermoplastics; weld‐line strength
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.26268

The injection molding process is widely accepted for the processing of engineering thermoplastics due to the ease of manufacturing complex designs. Weld‐line is a defect occurring in injection molded parts when two flow fronts join each other. At weld‐line locations, parts exhibit lower mechanical strength mainly due to inadequate intermolecular diffusion and fiber orientation anisotropy. The present work is aimed at investigating and comparing weld‐line strength for unfilled and glass‐filled polyamide‐6 materials. To achieve this, polyamide‐6 unfilled, 30% glass‐filled, and 50% glass‐filled materials are used to manufacture plaques. The special‐purpose mold is designed to obtain plaques with and without weld‐lines with help of Moldflow simulations. The specimens for tensile tests are then cut from molded plaques and experimental testing is conducted to evaluate tensile properties. Fractured surfaces of specimens are examined using a scanning electron microscope. The results demonstrated a significant drop in tensile strength and modulus for glass‐filled material weld‐line specimens when compared to specimens of no weld‐line. However, for unfilled specimens, tensile strength and modulus are almost the same for samples with and without weld‐line. A reduction in tensile strength of 13%, 49%, and 57% is observed for unfilled, 30% glass‐filled, and 50% glass‐filled polyamide‐6 material respectively. This work comprises, the comparative study of weld‐line tensile properties for three different polyamide‐6 materials. Experimental work is performed to evaluate the effect of weld‐line on tensile properties for unfilled, 30% glass fiber filled, and 50% glass fiber filled material. Scanning electron microscopy is done to support the results of the experiments.