High-Quality Foaming and Weight Reduction in Microcellular-Injection-Molded Polycarbonate Using Supercritical Fluid...

Area of Science:

• Materials Science
• Manufacturing Engineering
• Polymer Processing

Background:

• Microcellular injection molding (MuCell^®) with supercritical fluids (SCF) is key for weight reduction and carbon emission control.
• While nitrogen (N₂) is common, supercritical carbon dioxide (SCF CO₂) offers high solubility for greater weight reduction but poses challenges in foam control and cell uniformity.
• Gas counter pressure (GCP) has previously shown potential in improving foam quality.

Purpose of the Study:

• To investigate the effectiveness of SCF CO₂ foaming for polycarbonate (PC) materials in microcellular injection molding.
• To assess the impact of Gas Counter Pressure (GCP) on improving SCF CO₂ foaming quality in PC.
• To achieve significant weight reduction in PC parts for the electronics industry.

Main Methods:

• Microcellular injection molding experiments were conducted using supercritical CO₂ as the foaming agent.
• Key process parameters including SCF dosage, melt temperature, mold temperature, and injection speed were varied.
• Gas counter pressure (GCP) was applied to evaluate its effect on foam morphology and part properties.

Main Results:

• SCF CO₂ foaming of PC resulted in microcellular structures with cell sizes of 40 µm and densities of 3.97 × 10⁶ cells/cm³.
• Implementing GCP significantly refined the foam structure, reducing cell size to 20.9 µm and increasing cell density to 8.04 × 10⁶ cells/cm³.
• A weight reduction of approximately 30% was achieved, though GCP implementation may slightly impact the target weight reduction.

Conclusions:

• Microcellular injection molding of PC using SCF CO₂ is a viable method for producing high-quality foamed parts.
• GCP is an effective technique for enhancing foam cell uniformity and density when using SCF CO₂ in PC molding.
• This process offers a sustainable solution for weight reduction in PC components, particularly for electronics applications.