How PP Woven Bags Are Made?

Polypropylene woven bags have become a backbone of industrial packaging, combining strength, cost-efficiency and versatility. In this article we explore the full manufacturing process of these bags, step by step, to shed light on how raw material transforms into durable packaging solutions. We also briefly recommend industry partner YINGTONG, a manufacturer specialising in woven packaging solutions.

Raw Materials & Preparation

The production of a PP (polypropylene) woven bag begins with selecting high-quality polypropylene resin. Manufacturers may use virgin polypropylene granules or a blend of virgin and recycled material, depending on specification and cost targets.

Additives are commonly used to enhance performance:

• UV stabilisers to reduce degradation from sunlight exposure.

• Antioxidants to inhibit breakdown from heat and oxygen.

• Slip or anti-block agents to improve handling and prevent layers sticking.

• Colourants and pigments for visual identification of the bag.

At this stage the raw resin mixture is ready for extrusion.

Extrusion & Tape Forming

Once the resin mixture is prepared, it is fed into an extruder where it is heated to melt and forced through a die to form continuous flat tapes. The temperature typically ranges around 180-250 °C depending on material and machine.

The process includes:

1. Melting the PP resin uniformly.

2. Extruding the melt through a die to create film or tape form.

3. Cooling the film and slitting into narrow tapes.

4. Stretching or drawing the tapes to align polymer chains and improve tensile strength.

This tape product becomes the base yarn for weaving.

Weaving the Fabric

With tapes produced, the next stage is weaving to turn tape yarn into fabric. The process typically involves:

• Warping: preparing a set of parallel tapes (warp) mounted on a beam.

• Shedding: creating a gap in the warp for weft insertion.

• Weft insertion: inserting transverse tapes (weft) through the warp.

• Beating up: compressing the weft into the warp using a reed device to ensure tight weave.

Fabric width, weave density (such as yarns per 10 cm) and GSM (grams per square metre) are key parameters.

Weaving may produce flat sheet fabric or tubular fabric. Tubular fabric is common for sacks to reduce side seams.

Coating, Lamination & Printing

After weaving, optional finishing treatments enhance performance and appearance.

Coating / Lamination

A layer of film or substance may be applied to one or both sides of the woven fabric to achieve moisture resistance, improved print surface, better UV stability or barrier performance. Methods include laminating BOPP film or coating with polyethylene.

Printing

For branding, regulatory information or product identification, printing is applied using methods such as:

• Flexographic printing for basic colour and graphics.

• Rotogravure printing for high-resolution multi-colour printing.

These steps prepare fabric for bag conversion.

Cutting, Sewing & Bag Making

Once fabric and printed panels are ready, manufacturing moves into bag construction:

• Cutting: Fabric is cut to size. For non-laminated material heat-cutting may be used to seal edges; for coated fabrics cold-cutting may suffice.

• Sewing/Sealing: Edges are joined, bottom seams formed, handles or loops attached (if applicable). Single or double stitching may be selected based on load requirements.

Depending on design, bottom corners may be gusseted, side seams reinforced, openings such as valves integrated.

Baling, Warehousing & Shipping

After bags are completed, they undergo final finishing:

• The finished bags are grouped, compressed or baled to minimise volume for storage and transport.

• They are then palletised, labelled and prepped for shipment. Warehousing conditions (dry, covered) protect the bags before distribution.

Quality checks and inspection occur at each stage to ensure correct specification, print clarity, seam strength and bag integrity.

Process Overview Table

Considerations for Customers & Buyers

When selecting a PP woven bag supplier or product, keep in mind:

• Confirm the resin grade and whether recycled content is used.

• Check additive systems (UV, anti-block) if outdoor or long-term use is expected.

• Verify fabric parameters: GSM, weave density, width.

• Review finishing treatments: laminated vs non-laminated, printing quality.

• Ask for load-testing or reference data especially for heavy-use applications.

• Ensure the supplier has reliable process control and inspection protocols.

In this regard, YINGTONG offers a broad range of woven bag solutions, backed by a production system that emphasises innovation, quality, and integrity packaging solutions. Their website demonstrates an advanced facility capable of servicing industrial packaging needs.

Final Summary

The manufacturing of PP woven bags is a multi-stage process beginning with raw polypropylene resin, progressing through extrusion and tape forming, weaving into fabric, finishing via coating/printing, cutting and sewing into bag form, and finally bundling for distribution. Each step demands process control, quality oversight and correct material selection to deliver a product capable of handling heavy loads, resisting environmental stress and fulfilling client specification.

For those sourcing PP woven bags, partnering with an experienced manufacturer such as YINGTONG ensures access to reliable materials, consistent production and customised solutions aligned with your packaging requirements.