Why is calcium carbonate added to PP raffia tapes?
Calcium carbonate, usually added as filler masterbatch, lowers the cost of PP raffia, improves whiteness and opacity, reduces splitting (fibrillation) along the tape, and can improve printability and the bag's grip when stacked. Used correctly, it lowers cost per bag while keeping tape strength within specification.
How much calcium carbonate can PP tapes take?
Loading depends on the bag's required strength, tape denier and line speed. As a working guide, masterbatch is often added at a level that gives a few percent to around 15% calcium carbonate in the tape. Higher filler content lowers tenacity and elongation, so heavy-duty bags such as FIBC fabric use less filler than light cement or feed bags.
| Bag type | Strength demand | Filler direction |
|---|---|---|
| FIBC / jumbo bag fabric | Very high, safety-rated | Low |
| Cement and building-material bags | High | Low to medium |
| Fertiliser and chemical bags | Medium to high | Medium |
| Sugar, flour, grain and feed bags | Medium | Medium |
| Sand and general-purpose bags | Lower | Medium to high |
Which calcium carbonate grade suits raffia?
What problems does a poor filler cause on a tape line?
| Line problem | Typical filler-related cause |
|---|---|
| Frequent tape breaks in the stretching oven | Oversized particles, agglomerates, moisture |
| Holes or voids in the film | Moisture, volatile content |
| Low tenacity | Loading too high, poor dispersion |
| Screen changer pressure rising quickly | Coarse particles, poor dispersion, contamination |
| Greyish or yellowish tapes | Low brightness, iron impurities |
| Die lines and build-up | Excess free stearic acid |
How does calcium carbonate affect fibrillation?
Stretched PP tapes are highly oriented and tend to split lengthwise. Filler particles interrupt this orientation slightly, which reduces splitting during weaving and handling. This is one reason calcium carbonate is used even where cost is not the main driver.