How to Select the Right LDPE Granule for ACP Production

An aluminum composite panel (ACP) is a sandwich structure made by laminating a polyethylene core between two thin aluminum sheets. The panel's flatness, weight, bending strength, and line efficiency depend largely on the quality of the LDPE granule used in that core. The wrong granule choice leads to costly problems — surface waviness, delamination, and line stoppages. So how do you select the right LDPE granule?

1. Melt Flow Index (MFI) Compatibility

MFI measures the flowability of the polymer in its molten state. For the core to bond properly with the aluminum sheets on an ACP extrusion line, the MFI must both match the line's operating parameters and stay consistent from batch to batch. A fluctuating MFI causes thickness deviations and bonding problems. This is why consistent MFI is the first criterion to check when selecting a granule.

2. Purity and Contamination Control

Foreign matter, paper, metal particles, or other polymer contamination in the core turns into bubbles and weak points on the panel surface. A quality ACP granule must come from a well-sorted, filtered, and homogeneous source. The supplier's screening and filtration processes directly determine the quality of the finished product.

3. Color and Homogeneity

ACP cores are mostly produced from black granule, because black pigment masks the color variations coming from different recycling sources, providing a homogeneous and stable core. An even color distribution in the granule means a uniform cross-section appearance and consistent mechanical behavior in the panel.

4. Density and Mechanical Balance

The density of the core affects both the weight and the rigidity of the panel. The goal is to give the panel sufficient bending strength without adding unnecessary weight. The flexibility of LDPE is a decisive advantage in meeting the bendability and impact-resistance requirements of ACP.

5. Supply Continuity

No matter how good the technical specifications are, what keeps a production plan running is stable supply. A supplier who can guarantee monthly tonnage, maintain batch consistency, and meet the delivery schedule is as valuable to an ACP manufacturer as the granule itself.

At GranEx, we evaluate these criteria through a producer's eyes, not a supplier's. We learned firsthand how each granule behaves on an ACP factory line.