Coated bulk bags and uncoated bulk bags
Uncoated Bulk Bags & Coated Bulk Bags
Flexible Intermediate Bulk Containers are typically constructed by weaving together strands of polypropylene. Because of the weave-based construction, materials that are very fine may seep through the weave or sew lines.
Examples of these products include fine sands or powders. If you're packing a powder in an uncoated bag and you hit the side of a full bag, you will likely see a cloud of product leave the bag. The weave of an uncoated bag also allows air and moisture to more easily pass through the woven polypropylene to the product you're packing.
Common uses for uncoated bags:
For transporting or storing specific types of food grade and non-food grade products.
For transporting or sorting any product that is granular and is the size of grains of rice or larger such a beans, grain, mulch, and seed.
Transporting products/goods that need to breathe.
A “coated” bag is constructed similarly to an uncoated bag. Before the bag is sewn together, an additional polypropylene film is added to the bag's fabric sealing the small gaps in the poly weaves. This film can be added to the inside or outside of the bag.
Applying the film to the inside of the bag is the most common because it can keep products like powders from getting stuck in the weave when discharged. The coating can be difficult to detect if you're not very familiar with flexible intermediate bulk containers. The easiest way to tell if a fabric is coated is to press the weave together to see if it spreads apart. Make sure to test both the outside and inside of the bag. If the weave does not spread apart, there's a good chance the bag is coated.
One of the benefits of a coated bag is the additional protection it offers the materials being stored and/or transported. Flexible intermediate bulk containers can be found in warehouses, construction sites, and manufacturing facilities. These are environments where outside contaminants like dust, moisture, and dirt can be a factor. The coating on a bag can provide a moisture barrier and an added layer of protection. If you are packing a powder and strike the side of the bag when it’s full, you will not likely see a cloud of product exit the bag. Coated bags are very useful when packing small granular or powdered product.
Common uses for coated bags:
When a barrier from water or moisture is needed.
When you're transporting dry flowable products in powder, crystal, granule or flake form such as cement, detergents, flour, salt, fine minerals such as carbon black, sand and sugar that need moisture protection.
