A new microcellular injection molding process for polycarbonate using water as the physical blowing agent

This research investigated the effects of processing conditions on the shrinkage and warpage (S&W) behavior of a box-shaped, polypropylene part using conventional, microcellular, and microcellular co-injection molding. Three sets of 26-1 fractional factorial design of experiments (DOE) were employed to perform the experiments and proper statistical theory was used to analyze the data. After the injection molding process reached steady state, molded samples were collected and measured using an optical coordinate measurement machine (OCMM), which had been evaluated using a proper repeatability and reproducibility (R&R) measurement study. By analyzing the statistically significant main and two-factor interaction effects, the results show that the supercritical fluid (SCF) content (nitrogen in this case, in terms of SCF dosage time) and the injection speed affect the S&W of microcellular injection and microcellular co-injection molded parts the most, whereas pack/hold pressure and pack/hold time have the most significant effect on the S&W of conventional injection molded parts. Also, this study quantitatively showed that, within the processing range studied, a reduction in the S&W could be achieved with the microcellular injection molding and micro- cellular co-injection molding processes.

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

Materials ◽

10.3390/ma14154199 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4199

Author(s):

Dariusz Sykutera ◽

Piotr Czyżewski ◽

Piotr Szewczykowski

Keyword(s):

Injection Molding ◽

High Performance ◽

Flow Direction ◽

Cell Diameter ◽

Injection Molding Process ◽

Polyamide 66 ◽

Molding Process ◽

Sem Images ◽

Microcellular Injection Molding ◽

Sink Mark

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.

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Using P(Pressure)-T(Temperature) Path to Control the Foaming Cell Sizes in Microcellular Injection Molding Process

Polymers ◽

10.3390/polym13111843 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1843

Author(s):

Shia-Chung Chen ◽

Che-Wei Chang ◽

Chia-Yen Tseng ◽

En-Nien Shen ◽

Ching-Te Feng

Keyword(s):

Injection Molding ◽

Release Time ◽

Injection Molding Process ◽

Molding Process ◽

Foaming Agent ◽

Microcellular Injection Molding ◽

Cooling Speed ◽

Successful Control ◽

T Path ◽

Temperature Path

Microcellular injection molding technology (MuCell) using supercritical fluid (SCF) as a foaming agent is one of the important green molding solutions for reducing the part weight, saving cycle time, and molding energy, and improving dimensional stability. In view of the environmental issues, the successful application of MuCell is becoming increasingly important. However, the molding process encounters difficulties including the sliver flow marks on the surface and unstable mechanical properties that are caused by the uneven foaming cell sizes within the part. In our previous studies, gas counter-pressure combined with dynamic molding temperature control was observed to be an effective and promising way of improving product quality. In this study, we extend this concept by incorporating additional parameters, such as gas pressure holding time and release time, and taking the mold cooling speed into account to form a P(pressure)-T(temperature) path in the SCF PT diagram. This study demonstrates the successful control of foaming cell size and uniformity in size distribution in microcellular injection molding of polystyrene (PS). A preliminary study in the molding of elastomer thermoplastic polyurethanes (TPU) using the P-T path also shows promising results.

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About the numerous cost and processing advantages of the microcellular foam injection molding process for thermoplastics materials in the automobile industry

Analecta Technica Szegedinensia ◽

10.14232/analecta.2015.2.6-14 ◽

2015 ◽

Vol 9 (2) ◽

pp. 6-14

Author(s):

Alexandru Oprea-Kiss ◽

Imre Kiss

Keyword(s):

Injection Molding ◽

Automobile Industry ◽

Dimensional Stability ◽

Injection Molding Process ◽

Microcellular Foam ◽

Molding Process ◽

Microcellular Injection Molding ◽

And Performance ◽

Plastic Parts ◽

Foam Injection Molding

Today one of the goals of the automobile industry is to reduce weight. And physical foaming has already demonstrated its potential in this sector, improving the value and performance of applications under the bonnet: engine and gearbox cases, inlet air filters, cockpits, radiator baffles and so on. Around the world, the microcellular injection molding (MuCell) is used in thousands of applications in the automotive, packaging, technical molding, office machinery and electric and electronic component industries. The research opportunities purpose is to obtain even lighter pieces, with greater dimensional stability and with an excellent surface finish, in other words, perfect plastic parts. More component functionality with reduced weight, and cost control at the same time: MuCell is a process to physically foam thermoplastics, which combines technical and economic objectives. Besides weight reduction, it also provides improved dimensional stability of the moulded parts.

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