How Bulk Bags Are Made: The Complete Manufacturing Process

Bulk bags, also known as Flexible Intermediate Bulk Containers (FIBCs), are essential for your transportation needs, but how are they actually made? What makes bulk bags strong enough to handle all of your material?

At FlexSack, we have over 70 years of combined experience in the FIBC industry, and we take pride in our comprehensive manufacturing process, ensuring the highest quality for our customers. 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. This flexible fabric is designed to be strong and versatile for the transporting of dry and flowable products. At FlexSack, we manage over 365 different specifications in our inventory, ensuring that we can meet any unique requirement our clients may have.

How is FIBC Fabric Made?

FIBC fabrics are made with the following process:

The Extrusion Process

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 colored 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%

Weaving the Bags

During the weaving process, the polypropylene tapes made during the extrusion process are loaded onto looms, and the fabric that forms the body of 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 the transportation and storage of various materials but ill-suited for other products.

Coating (Lamination) Process

Depending on the application, the fabric can be treated with a 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 used for the lamination process is typically composed of:

• PP 350 FG 75%
• LD 1070 LA17 25% (No filler is used in the 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.

Phase 2: Cutting, Component Manufacturing, and Sewing

Now that We’ve reviewed how our bulk bag fabrics are produced through extrusion, weaving, and coating. Next, we’ll discuss the production process’s second phase, including fabric cutting, component manufacturing, and sewing.

The Cutting Process

During the cutting stage, the rolls of woven fabric that were produced during weaving are moved to the cutting floor, where the woven fabric is cut into specific shapes and sizes based on the finished bag’s specifications. The cuts determine the shape of the bag’s body panels, base and top panels, duffle or spout dimensions, and the bag style. Measurements are programmed automatically to ensure the dimensions for each cut are equal and exact according to the given specifications.

Component Manufacturing

This stage involves two sub-stages: printing and webbing.

Printing the Bags

After the fabric is cut, the printing plan is defined by the planning team after print plates have been produced. After the plan is determined, the data is sent to the automatic printing machine, at which point the impressions, company logo, and colors are applied to the bag fabric.

Printing is applied to the body fabric panels before any sewing processes.

Webbing for Strength

During this stage, the various webbing components that are to be included in the finished bag are produced, including lift loops, perimeter bands or safety bands, belly bands, web ties, etc. Here, polypropylene tapes are woven on flat looms in the warp (vertical) direction, and the multifilament yarn is woven in the weft (horizontal) direction to produce the webbing to support 6,000lb break strength.

The Sewing Process

Once all the fabrics are cut, the components are produced, and the technical team has reviewed the production plan, the materials are brought onto the production floor for the sewing process to begin. The line plan is set up based on the attachments and components of each bag.

Sewing generally follows as such: spouts are attached to their appropriate panels, the “box” (body panels of the bag) is sewn together using a single safety stitch, and finally, the web components and accessories are attached to the bag with the finishing stitch. Different operations are carried out at their respective workstations by trained specialists to produce the finished FIBC bag.

What Are Bulk Bags Used For?

Bulk bags, or FIBCs, are used across various industries due to their versatility and strength. Here are some common applications:

1. Food Industry: Ideal for transporting grains, seeds, flour, sugar, and other bulk food items.
2. Hazardous Materials: Used to safely transport chemicals, minerals, and other hazardous substances.
3. Recyclables: Commonly used for collecting and transporting recyclable materials like paper, plastic, and metals.
4. Aggregates: Perfect for transporting sand, gravel, and other construction materials.
5. Pharmaceuticals: Used to handle pharmaceutical powders and ingredients safely.
6. Chemicals: Ideal for transporting various chemicals in bulk quantities.
7. Mined Products: Suitable for carrying minerals and ores.
8. Agricultural: Used for transporting animal feed, fertilizers, and other agricultural products.
9. Plastics and Pigments: Suitable for carrying plastic granules, pigments, and other raw materials.

About FlexSack

For more than 25 years, ABC Polymer Industries has been delivering bulk bags to customers throughout North America. Now under the name FlexSack, we’re committed to continuing to thrive on the reputation we’ve developed through the years. With experts in bulk bags, super sacks, FIBCs, and more, plus dedicated resources to managing our business, we’re focused on providing the best customer service experience possible while operating under a “relationship-first” approach. We often joke that we’re the best-kept secret in the bulk bags industry; a sentiment echoed by some of our most loyal customers.