Enhancing the Fatigue Strength of the Weld Line in Advanced Polymer Injection Molding: Gas-Assisted Mold Temperature Control for Thermoplastic Polyurethane (TPU) Composites

Abstract

This study presents an innovative approach to enhancing weld line strength in advanced polymer injection molding through applying gas-assisted mold temperature control, significantly increasing mold temperature beyond typical values observed in conventional processes. We investigate the effects of various heating times and frequencies on the fatigue strength of Polypropylene (PP) samples and the tensile strength of Acrylonitrile Butadiene Styrene (ABS) composite samples at different Thermoplastic Polyurethane (TPU) percentages and heating times. Using gas-assisted mold heating, mold temperatures exceeding 210 °C are achieved, which represents a significant advancement compared to the standard mold temperatures of less than 100 °C. As a result, the fatigue strength of the PP sample with mold heating at 15 s shows a remarkable increase of up to 5.4 times at 5 Hz compared to the sample without mold temperature control. Moreover, ABS/TPU blends with 15 wt.% TPU exhibit the highest ultimate tensile strength (UTS) value of 36.8 MPa, while blends with 30 wt.% TPU have the lowest UTS value of 21.3 MPa. This advancement demonstrates the potential for improved welding line bonding and fatigue strength in manufacturing. Our findings reveal that increasing the mold temperature before injection results in higher fatigue strength in the weld line, with the TPU percentage having a more significant influence on the mechanical properties of ABS/TPU blends than heating time. The results of this study contribute to a deeper understanding of advanced polymer injection molding and offer valuable insights for process optimization.

Analysis of Weld Lines in Micro-Injection Molding

“…Viscosity decreases with increasing mold temperature; such a decrease favors the formation of a flowing weld line (thus a reduction of the cold weld line length). This finding is consistent with those already reported in the literature on the effect of mold temperature on the mechanical performances at the weld line for conventional injection molding process [23].…”

“…Due to the high-velocity gradient, molecules in the skin region experience an orientation in the flow direction. In the core, the flow is weak and molecules are stretched by the fountain flow and are then pushed towards the edge regions, ending up being parallel to the weld line [23]. In the literature, weld lines can be distinguished into two main types: cold or stagnating weld lines, formed by a head-on impingement of two melt fronts, and hot or flowing weld lines, occurring when two melt streams continue to flow after their lateral collision [4].…”

Mechanical Properties and Influence Factors of Ordinary Shear Links

“…The application of ordinary shear links in the K-type eccentrically braced frame can be intensively studied in the future. (6) The failure process of the specimens includes large steel plate deformation, and this deformation was observed with the naked eye. Visualization software could be used to monitor tiny deformations in future research.…”

“…Eccentrically braced steel frame structures have been widely applied at home and abroad, and shear links are a typical energy-dissipating component of an eccentrically braced frame [1,2]. Eccentrically braced steel frame structures dissipate seismic energy through inelastic deformation of shear links and effectively ensure that columns, supports, non-energy-dissipating beams and other components are in the elastic stage [3][4][5][6][7]. A significant characteristic of the eccentrically braced steel frame structure is that damage occurs in predesigned shear links, protecting the connecting nodes from damage.…”