High-Performance of a Thick-Walled Polyamide Composite Produced by Microcellular Injection Molding

Abstract

Lightweight moldings obtained by microcellular injection molding (MIM) are of great significance for saving materials and reducing energy consumption. For thick-walled parts, the standard injection molding process brings some defects, including a sink mark, warpage, and high shrinkage. Polyamide 66 (PA66)/glass fiber (GF) thick-walled moldings were prepared by MuCell® technology. The influences of moldings thickness (6 and 8.4 mm) and applied nitrogen pressure (16 and 20 MPa) on the morphology and mechanical properties were studied. Finally, the microcellular structure with a small cell diameter of about 30 μm was confirmed. Despite a significant time reduction of the holding phase (to 0.3 s), high-performance PA66 GF30 foamed moldings without sink marks and warpage were obtained. The excellent strength properties and favorable impact resistance while reducing the weight of thick-walled moldings were achieved. The main reason for the good results of polyamide composite was the orientation of the fibers in the flow direction and the large number of small nitrogen cells in the core and transition zone. The structure gradient was analysed and confirmed with scanning electron microscopy (SEM) images, X-ray micro computed tomography (micro CT) and finite element method (FEM) simulation.

Microcellular injection molding of foamed engineering plastic parts with high dimensional accuracy

“…The thermal properties of POM and PA66 raw materials would significantly affect the processing conditions and shrinkage behavior during the cooling period after the products were fabricated. It is essential to guarantee that both gears were prepared in the proper situation, and subsequently underwent the same shrinkage process 27 . The TGA measurement was used to investigate the decomposition behavior of the raw materials since POM and PA66 require harsh processing conditions in injection molding.…”

“…It is essential to guarantee that both gears were prepared in the proper situation, and subsequently underwent the same shrinkage process. 27 The TGA measurement was used to investigate the decomposition behavior of the raw materials since POM and PA66 require harsh processing conditions in injection molding. The degradation temperature, degradation time, and char residual of raw materials are important for directing the processing conditions.…”

Structure Analysis and Its Correlation with Mechanical Properties of Microcellular Polyamide Composites Reinforced with Glass Fibers

“…Molding of 6 mm and 8.4 mm thick samples 6 mm and 8.4 mm molded pieces, here described as thick-walled samples, were produced using an Engel Victory 500 (Engel, Schwertberg, Austria) injection molding machine, in a four-cavity injection mold [28]. MuCell ® technology (Trexel, Wilmington, MA, USA) was applied as a microcellular injection process.…”

“…The dimensions of obtained 6 mm and 8.4 mm thick molded pieces were 1.5 and 2 times higher compared to PN-EN ISO 527-2:2012 [35] type 1B samples, respectively. 24 × 4.2 mm and 21 × 4.1 mm (wide × deep) gap gates were applied for 8.4 mm and 6 mm specimens, respectively, in the mold cavity [28]. Injection molding parameters are summarized in Table 3.…”

“…SEM and micro-CT techniques reveal a typical skin-shell-core structure in the case of PA reinforced with glass fibers [8,13]. In contrast, the microcellular form has an additional transition layer [8,27,28], which causes such a three-phase structure to be even more complicated to investigate using the commercial micro-CT apparatus applied in this research.…”