How Bulk Bags Are Made: Part 1

Part 1: Extrusion, Weaving, Coating

Bulk bags are essential for your transportation needs, but how are they actually made? What makes bulk bags strong enough to handling all of your material? Here’s the SackFacts that you should know about FIBC fabrics and how bulk bags are made.

What is FIBC fabric?

FIBC fabrics are usually made from polypropylene and are coated with a synthetic film made of polypropylene and polyethylene. Flexible fabric is designed to be strong and versatile for the transporting of dry and flowable products.

How is FIBC fabric made?

FIBC fabrics are made with following process:

  1. Extrusion
  2. Weaving
  3. Coating (Lamination)


The Extrusion process is where a mix of virgin ingredients (raw materials) are melted into tapes of a specific measurement. The ingredients used in this process include Polypropylene (PP) granules, a small amount of calcium carbonate, a chemical UV stabilizer, and coloured pigments if required. The tapes are loaded onto bobbins in preparation for weaving.

FIBC Fabrics are typically composed of:

  • Polypropylene 94.33%
  • Calcium 3.77%
  • UV treatment 2%


During the weaving process, the polypropylene tapes made during the extrusion process are loaded onto looms and the fabric that forms the body for the bulk bag is woven into shape. The resulting weave is made up of warp (vertical tapes) and weft (horizontal tapes) generally at 10-warp x 10-weft tapes per square inch. At this point, the fabric possesses small gaps between the weave and is thus subject to the passage of moisture and fine particles. In essence, the material is breathable which can be excellent for transportation and storage of various materials, but ill-suited for other products.

Coating (Lamination)

Depending on the application, the fabric can be treated with special laminate referred to as “coating”. Coating or Laminating is a process in which the fabric passes through a thin, liquid film of PP & LDPE material produced by a flat die and is then solidified by chilled rollers. The benefit of coating the fabric is that it seals the voids in the weave and enhances the physical properties of the fabric. Lamination is essential for bulk bags that are used to transport fine or flowable products and for any product that must not be exposed to moisture.

The material that is used for the lamination process is typically composed of:

  • PP 350 FG 75%
  • LD 1070 LA17 25% (No filler is used in lamination process)

Following the coating process, if applicable, the woven fabric is wound onto large spools and stored until it enters the cutting process, which starts Phase 2 of production.


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