PP Woven Bag Manufacturing Process Explained

Pp Woven Bag manufacturing warehouse overview

1. Introduction to PP Woven Bags and Manufacturing Technology

Polypropylene is a semi-transparent, semi-crystalline thermoplastic material known for:

• High tensile strength

• Excellent electrical insulation

• Low water absorption

• High heat-setting temperature

• Low density and high crystallinity

These properties make PP the most suitable raw material for Woven Bags. In practical production, modified fillers such asglass fiber, mineral fillers, and thermoplastic elastomers are often added to optimize performance or reduce cost.

Pp Woven Bags are widely used in:

• Agricultural packaging (grains, seeds, feed)

• Cement and chemical packaging

• Food outer packaging

• Geotechnical engineering

• Logistics, transportation, and flood control materials

2. Classification of PP Woven Bags

Types of Pp Woven Bags

According to structure and processing method, woven products are generally classified into three categories:

1. Plastic woven bags (non-laminated woven bags)

2. Laminated PP woven bags

3. Woven fabrics (roll materials)

3. Overall Manufacturing Process of PP Woven Bags

3.1 Manufacturing Process of Non-Laminated Woven Bags

The woven fabric is converted into finished bags through the following steps:

• Printing

• Cutting

• Sewing

Depending on the equipment configuration, production can be arranged as:

• Cutting before printing

• Printing before cutting

Automatic cutting and sewing machines can continuously complete printing, cutting, and sewing, and are capable of producing valve bags, bottom-filled bags, and other special structures. For plain woven fabric, center seam bonding or sewing can be applied before bag making.

3.2 Manufacturing Process of Laminated PP Woven Bags

Laminated woven bags are produced by laminating or coating woven fabric with plastic film or paper.

• Laminated tubular or flat fabric can be:

  • Cut, printed, and sewn into standard sewn-bottom bags

  • Punched, hemmed, printed, and sewn into cement bags

• Laminated flat fabric can be:

  • Center-seam bonded, printed, cut, and bottom-sealed to form pasted-bottom bags

• Through welding and winding processes, the material can also be used to produce tarpaulins and geotextiles.

Plain woven fabric, with or without coating, is also commonly used for tarpaulins and geotextile products.

4. Key Processing Methods and Technologies

Key technologies in PP woven bag production

4.1 Granulation Process

Granulation is a critical step in plastic processing and directly affects the stability and quality of subsequent tape stretching and weaving.

Granulation process flow:

Compounding → Extrusion → Filtration → Water Cooling → Haul-off → Pelletizing → Drying → Packaging

Granulation Process Description

• PP powder, additives, and activated calcium carbonate are mixed in a high-speed mixer according to the formulation

• The blended material is fed into the extruder via a screw feeding system

• The material is melted, plasticized, and extruded into continuous strands under stable pressure

• Strands are cooled in a water bath, dehumidified, and air-cooled

• Pellets are formed, screened, fluidized-bed dried, and stored in silos

• Qualified pellets are finally weighed and packed

Stable granulation ensures consistent tensile strength and processing performance of the woven bags.

4.2 Tape Stretching (Flat Yarn Stretching)

Tape stretching, also known as flat yarn stretching, is the core process of PP woven bag manufacturing and has a decisive impact on bag strength and durability.

Key Technical Factors in Flat Yarn Production

• Raw material modification and blending ratio

• Anti-aging and anti-degradation systems

• Extrusion temperature control (190–250°C)

• Pressure and flow stability

• Stretching ratio and blow-up ratio

• Crystallization cooling and molecular orientation

• Heat setting and pre-shrinking

Flat Yarn Stretching Process

1. Raw materials are fully plasticized in the extruder under high temperature

2. Molten material is extruded through the die to form a thin film

3. The film is cooled and slit into tapes

4. Tapes are stretched and oriented in a high-temperature oven

5. Heat setting is performed on heated rollers

6. Cooling rollers stabilize the structure

7. Flat yarns are wound by a differential tension winding system

The quality of flat yarn directly determines whether the woven bag is strong, durable, and resistant to breakage.

5. Conclusion

PP woven bag manufacturing is not a simple bag-making process, but a systematic industrial operation highly dependent on formulation control, equipment precision, and process stability.

From granulation to tape stretching, weaving, and bag conversion, every step influences the final product performance and service life.

For buyers, engineers, and importers, understanding the manufacturing process is the most effective way to identify reliable and professional PP woven bag manufacturers.