LDPE Granule for Film & Bag Production: 5 Factors That Define Quality

In plastic bag and film production, the strength, appearance, and line efficiency of the final product depend largely on the quality of the LDPE granule used. Even with the same machine, the same die, and the same operator, the wrong granule leads to costly problems — film breaks, gels (fish-eyes), holes, and printing defects. The key to producing quality film and bags from recycled LDPE granule is choosing the right raw material. So what should you look for in LDPE raw material for film production?

1. Melt Flow Index (MFI) and Processability

On a blown film line, the bubble must inflate steadily and the film gauge must stay even — which requires the MFI to sit in the right range and stay consistent from batch to batch. Too high an MFI destabilizes the bubble; too low overloads the motor and slows production. A consistent MFI directly determines your line speed and film quality.

2. Gel and Contamination Control

The most common defect in film is the "gel" — the small hard specks known as fish-eyes. They usually come from poorly melted polymer, foreign matter, or contamination with a different melting point. Gels both spoil the appearance and cause the film to tear or puncture at that point. A quality film granule must be well-filtered, homogeneous, and low in contamination.

3. Mechanical Strength

Tear, puncture, and dart-impact resistance are critical, especially for carrier bags and bin liners. The flexibility and elongation of LDPE deliver high strength even in thin film. A consistent molecular structure and purity in the granule guarantee the same strength in every batch.

4. Color and Appearance

In black bags, black granule masks the color differences between various recycling sources, giving a homogeneous look. Natural (honey-colored) granule, on the other hand, suits producers who need coloring and printing flexibility. An even color distribution in the granule determines masterbatch compatibility and the appearance of the finished film.

5. Supply Continuity

Film and bag production is a high-tonnage, continuously running operation. However good the technical specs are, what feeds the line is stable supply. A supplier who can guarantee monthly tonnage, maintain batch consistency, and meet the delivery schedule is vital to a film producer.

At GranEx, we evaluate these criteria through a producer's eyes, not a trader's. We learned firsthand how each granule behaves on the extrusion line.