The answer comes down to three critical factors: machine quality, raw material selection, and workforce expertise.

1. Machinery Quality & Yarn Consistency

In theory, when PP resin (plastic pellets) is processed through an extruder machine, the quality and consistency of the yarn produced are critical. The yarn must be even and uniform.

Recommended machinery brands include Starlinger (Austria), Lohia (India), and HengLi (China/Taiwan).

If the yarn thickness is inconsistent, it reduces the yarn’s flexibility and longevity, ultimately weakening the strength of the finished woven bag after stitching.

After extrusion, the next stage is the weaving process. A high-quality weaving machine produces neat and uniform fabric. The woven “fabric” will be stronger when it is flat and evenly structured.

For export orders, the standard typically requires flat yarn and neatly woven fabric. If the woven fabric appears curled or uneven (not flat), it is advisable not to export until production experience and quality standards are improved.

Export quality cannot be compromised, as there is always a risk of container rejection.

Therefore, it is better to have a thinner bag with proper specifications than a thicker bag that is uneven and poorly woven.

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2. Raw Material Selection

For optimal results, it is recommended to use Virgin PP (pure polypropylene resin).

A small percentage of additives may be used, such as:

• Calcium (around 5%)

• High-quality recycled PP (e.g., processed from clean sources like water cups)

Important note: Any lids or non-PP components must be removed before recycling into pellets.

With high-quality machinery, a recommended ratio would be:

• 70% Virgin PP

• 25% High-quality Recycled PP

• 5% Calcium

One major reason why a thick bag may burst is the excessive use of calcium or recycled PP, which reduces material strength despite increased thickness.

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3. Lamination Temperature Control (PP Extrusion)

Another critical factor is the temperature during the lamination process (PP Extrusion).

If the temperature is too high, excessive overheating may occur on either the Printed OPP layer or the woven plastic surface. This can weaken the bag structure and make it more prone to bursting.

If the temperature is too low, the bonded OPP layer may peel off easily.

Therefore, skilled operators are essential to maintain the correct and precise temperature balance.

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Conclusion

Thickness alone does not determine strength.
Machine quality, raw material composition, and skilled workmanship are far more important factors in ensuring durable and reliable Rotogravure woven bags.