Information on Bulk Bags

What You Should Know About FIBCs
To support your decision-making as an FIBC purchaser, InterBULK has compiled the following information on bulk bag terminology, construction, strength and characteristics. For more information on bulk bags and material handling topics please visit Powder and Bulk Dot Com.

Polypropylene (PP)
PP is a long chain synthetic olefin polymer. It is a thermoplastic material, meaning it can be repeatedly heated to its softening point, shaped, worked or drawn in the case of fibers, then cooled to preserve its shape. The drawn fibers or yarns are used to construct the finished geotextile. PP is widely used in geotextiles because of its relatively low cost, and because it can easily be formed into a variety of fiber and yarn sizes.

Bulk Bag Material
InterBULK bulk bags are made from extruded sheets of polypropylene film, which are cut into thin strips and wound onto bobbins. These strips are referred to as tapes. The tapes can vary in thickness and width, depending on the application of the material. The tapes are then woven into material that will be used to construct the various parts of the intermediate bulk containers. Because the polypropylene material used to make bulk bags is woven, the terms used to describe the material are identical to those used in the textile industry.

Material Strength
Suppliers and consumers of polypropylene bags usually describe material by its areal density. Areal Density is the dry fabric weight. The most common unit of measure is ounces per square yard, often abbreviated as ounces. A fabric with a weight of 6.5 oz has an areal density of 6.5oz/sq. yd. InterBULK bulk bags are available in one of three weights: 6.0oz (1600D/14x14), 6.5oz (1700D/14x14) or 8.0oz (2100D/14x14) material.

To describe the strength of the tape, the industry uses the term Denier. Denier is a numbering system for yarn and filament in which yarn number is equal to weight in grams of 9000 meters of yarn. The Denier rating is directly correlated to the thickness of the tape. For example, InterBULK produces main body fabric from tape that is 1500 to 2100 Denier. For the duffel or spout material, we use tape that is 900 Denier. The difference between these two materials rests in the thickness or width of each tape.

The weave density of the material also affects bag strength. Vertical tapes are known as the warp and horizontal tapes as the weft. The weave density refers to the number of warp tapes and weft tapes per square inch of fabric. For example, a 14 x 14 fabric has 14 vertical tapes (warp) and 14 horizontal tapes (weft) per square inch. Material can be strengthened by making either the warp or weft tapes thicker, or by increasing the weave density.

Tensile strength another term that is used to describe the strength of the material used to construct the intermediate bulk containers. Tensile strength is measured by pulling a 1.97 inch (5 cm) wide strip of cloth until it breaks. For example, a 1700D/14x14 weave has a tensile strength of 485 lbs/in².