Mechanism of Aluminum Paste: Why the Metallic Effect Comes from “Flakes” Rather Than “Particles”

1.1 Flake Size Ratio Determines Mirror Reflection

The brightness of ink-grade aluminum paste is not determined by particle size, but by the flake aspect ratio (≥200:1). The thinner the flake, the higher the proportion of light that undergoes mirror reflection on the surface of the aluminum paste, resulting in a stronger metallic feel.

1.2 Non-floating Orientation Enhances Opacity

Non-floating aluminum paste is influenced by resin shrinkage stress during the drying process, causing the aluminum flakes to orient parallel to the substrate. This creates a continuous metal layer, increasing the reflective area per unit area and boosting opacity by over 25%.

II. Silver Arrow Aluminum Paste Process: From Atomized Aluminum Powder to Finished Ink-grade Aluminum Paste

2.1 Raw Materials: 99.85% High Purity Atomized Aluminum Powder

The spherical aluminum powder with D50 ≤ 6 µm provides a uniform starting point for subsequent flaking. The impurity content (Fe + Si) is ≤ 0.15%, reducing the risk of hydrogen evolution in later stages.

2.2 Wet Ball Milling: Ester-based Closed-loop System

• Medium: A co-distillation system of n-propyl acetate and butyl acetate, with a polarity index of 4.3, is compatible with NC, PU, and acrylic resins through hydrogen bonding.
• Grinding Media: Zirconia beads of Φ0.8–1.0 mm, line speed 12 m/s, achieving precise D50 after 6 hours at 7/9/10/12/14 µm across five grades.

2.3 Surface Passivation: Dual-layer Coating

A phosphate ester layer provides anchorage, while a silane layer offers hydrophobicity. The overall thickness is 3–5 nm, with a hydrogen evolution rate of <0.1 mL·g⁻¹·24 h, ensuring long-term storage stability for the ink-grade aluminum paste.

III. Silver Arrow Aluminum Paste Performance Table for 2P Series Ink-grade Aluminum Paste

*Opacity: ΔE on black-and-white cardboard, 25 µm scratch sample.

IV. Application Formulation Examples

4.1 Food-grade Paper Gravure Ink

• Silver Arrow Aluminum Paste 2P-10: 12%
• NC Resin (30 mPa·s): 25%
• PU Resin (OH=120): 5%
• Ester Solvents: 55%
• Dispersing Agent (BYK-220 S): 1%
• Defoamer: 0.5%

Process: 800 rpm pre-dispersion for 10 min → Three-roll mill to 5 µm → Scraper fineness ≤10 µm → Printing film thickness 12 µm → 60°C hot air for 10 s → 60° Gloss 520 GU, tape test 100/100.

4.2 Plastic Film Surface Printing Ink (BOPP)

• Silver Arrow Aluminum Paste 2P-12: 10%
• CPP Resin (Cl=24%): 20%
• Ester/Ketone Mixed Solvent: 65%
• Polyamide Wax (anti-settling): 0.8%

Process: Same as above, with 500 times rub resistance, ΔE<1.0.

V. Conclusion: Three Reasons to Choose Silver Arrow Aluminum Paste

1. Environmentally Compliant: Zero benzene and ketone, VOCs reduced by 30%, directly meeting regulations for cigarette and food packaging inks.
2. Stable Performance: Precise classification of five particle sizes, with D90/D10 ≤ 2.4 in the same batch, and ΔE<0.5 for print color fluctuations.
3. Technical Support: From aluminum paste selection and formula optimization to printing processes, Silver Arrow's technical center offers 24-hour online response. When searching for the best solution for “aluminum paste, ink-grade aluminum paste, Silver Arrow aluminum paste,” the 2P series has already proven, with data and case studies, that metallic feel, opacity, and environmental friendliness can coexist