The manufacturing process of FIBCs is relatively complex, requiring multiple steps, each of which directly impacts the quality of the final product.
The raw material preparation stage primarily uses polypropylene or polyethylene resin as the main raw material, with a small amount of auxiliary materials added and mixed evenly.
These plastic raw materials are fed into an extruder for melt extrusion to form a plastic film. This film is then cut into filaments, stretched at a temperature below the resin's melting point, and produced as high-strength, low-elongation flat yarns through molecular orientation and heat setting.
The subsequent weaving process involves warping, weaving, and laminating the flat yarns to create a woven plastic fabric as the base fabric. The quality of the base fabric directly determines the load-bearing capacity and durability of the FIBC. Generally, the tensile strength of the base fabric needs to meet certain standards, such as a longitudinal tensile strength greater than 1470 N/5 cm (for FIBCs with a load capacity of less than 1 ton).
The production of the straps is equally important, requiring processes such as mixing, drawing, and weaving. In recent years, a type of sling made from split yarn has been increasingly widely used due to its low weight, high tensile strength, and aesthetic appeal.
The final step is sewing, where the base fabric is sewn to the slings and webbing to create a flexible container bag. Sewing must be straight, without any loose stitches, broken threads, or floating threads. There should be no loose stitches or overstitches, and each stitch should be backstitched at least three times to ensure seam strength.