Investigation of the Influence of Fiber Content, Processing Conditions and Surface Roughness on the Polymer Filling Behavior in Thermoset Injection Molding

Abstract

A completely opposite injection molding filling behavior of thermosets and thermoplastics by an effective and useful method developed by the authors was found. Specifically, for the thermoset injection molding, there is a strong slip between the thermoset melt and wall surface, which is not found for the injection molding of thermoplastic materials. In addition, the variables, such as the filler content, the mold temperature, the injection speed, and the surface roughness that could lead to or influence the slip phenomenon of thermoset injection molding compounds, were also investigated. Furthermore, microscopy was conducted to verify the correlation between the mold wall slip and fiber orientation. The results obtained in this paper open challenges in the field of the calculation, analysis, and simulation of mold filling behavior of highly glass fiber-reinforced thermoset resins in the injection molding process with consideration of wall slip boundary conditions.

Flow Disturbance Characterization of Highly Filled Thermoset Injection Molding Compounds behind an Obstacle and in a Spiral Flow Part

“…It can be seen from Figure 7 , Figure 8 and Figure 9 that the thermoset melt dyed a white color on the surface of the injected parts moves from the original painted position to near the melt front, a phenomenon also observed in previous publications [ 27 , 29 , 32 ]. The movement of the polymer dyed a white color is attributed to the wall slip between the phenolic polymer and the mold wall surface.…”

“…Firstly, a simple standard two-plate mold was employed to study the weld lines formation mechanism of selected materials. In the experimental process, the mold painting method developed by the authors and published in the previous article continued to be employed [ 32 ]. A white mark was painted on a fixed location of the mold wall surface.…”

“…Previously published articles have shown that the mold-filling behavior of highly filled thermoset injection molding compounds is completely different from thermoplastic materials. Specifically, the mold-filling characterization of these materials in the injection molding process is a plug flow [ 27 , 28 , 29 , 30 , 31 , 32 ] instead of fountain flow, which is found for thermoplastic materials. In the filling phase of the injection molding process, there is a strong slip phenomenon between the thermoset melt and the wall surface, which is not found for the injection molding of thermoplastic materials.…”

“…In the filling phase of the injection molding process, there is a strong slip phenomenon between the thermoset melt and the wall surface, which is not found for the injection molding of thermoplastic materials. In addition, the effect of the filler content; the processing condition, such as the mold temperature; the injection speed; and the surface roughness of both the cavity and the core on the polymer filling behavior in the thermoset injection molding process [ 32 ] was successfully investigated and analyzed using the mold printing method, as shown in Figure 1 . The slip phenomenon between thermoset melt and the mold wall surface was studied and explained via an analysis of the visualizable movement of the thermoset melt dyed white on the surface of the injection-molded parts.…”

“…A lower filler amount and injection speed and a higher mold temperature and surface roughness decreased the wall slip phenomenon of the thermoset melts. Because of this wall slip phenomenon, the velocity profile of the molten thermoset on the interface between the thermoset melt and the mold wall surface must be different from zero [ 32 ], which is completely different from the velocity profile of molten thermoplastic materials. ( Figure 2 ) Consequently, the mechanism of weld line formation and the development of high-filled thermoset melt in the filling phase is different from the previously stated knowledge of the theory about the weld line formation of thermoplastic materials.…”