Why price per kilogram is incomplete

A purchasing quote measures the price of an input. A film factory earns money by shipping acceptable finished products. The more useful metric is total cost per saleable kilogram, roll or thousand bags. Resin and masterbatch prices matter, but so do rejects, line speed, labor, power, maintenance and product failures.

Start with a weighted material cost

If a finished blend contains 92% PE resin at $1.20/kg and 8% filler masterbatch at $0.70/kg, its theoretical material cost is (0.92 × 1.20) + (0.08 × 0.70) = $1.160/kg. The unfilled PE reference is $1.200/kg. This illustrative difference is $0.040/kg, or about 3.3% of the reference material cost. These are example prices, not current market quotations or guaranteed savings.

Separate masterbatch loading from mineral content

An 8% masterbatch addition is not necessarily an 8% mineral addition. If two suppliers use different mineral concentrations, comparing their quoted price per kilogram without accounting for effective formulation and performance can be misleading. Ask for the relevant specification and calculate the complete blend rather than comparing pellets in isolation.

Account for yield and scrap

Suppose a process uses $1.160/kg of raw materials but only 95% of the processed material becomes saleable output. Ignoring recovery credits, material cost per saleable kilogram is approximately $1.160 ÷ 0.95 = $1.221. A reference process costing $1.200/kg at 99% yield has a comparable figure of $1.212. In this example, the lower-priced formulation loses its apparent advantage because of higher scrap. Actual accounting should reflect whether regrind is recovered and reused.

Check output, thickness and bag count

Mineral-filled formulations can change melt behavior, density, film gauge control and processing stability. A change in density may affect the number of bags produced per kilogram at the same thickness and dimensions. Therefore, compare finished units that meet the same dimensional and performance requirements. Record line speed, kilograms per hour, actual thickness distribution and bags per kilogram.

Include quality and downstream operations

Poor dispersion may create specks or defects. Changed sealing behavior can raise conversion scrap. Opening or winding problems can slow bag-making equipment. The costs of additional inspection, rejected rolls and customer complaints belong in the decision even if they are harder to estimate than resin prices.

A supplier comparison worksheet

For each trial record resin grade and price; filler masterbatch grade, concentration, dosage and price; production output; scrap percentage; average film thickness; MD/TD mechanical test results; haze or appearance criteria; sealing and conversion performance; and cost per acceptable finished unit. Use the same trial duration and quality thresholds when comparing candidates.

When a higher-priced grade wins

A more expensive masterbatch may still deliver a better outcome if it allows more consistent film, lower reject rates or a higher validated dosage. Conversely, a lower-cost grade may be sufficient for a less demanding opaque application. The correct choice is determined by tested performance and the customer’s end-use needs, not brand claims.

Conclusion

Evaluate Na₂SO₄ filler masterbatch through total production economics. Price is one input; usable output, film quality and repeatability determine whether a cost-saving formulation actually saves money.

Frequently Asked Questions

Is one filler dosage suitable for every blown film line?

No. Resin grade, film structure, gauge, equipment, masterbatch composition and finished-product requirements change the workable range.

Should a supplier’s case-study result be used as a guarantee?

No. Treat it as a starting point for a controlled trial, then verify results against your own film specification.

What is the next step before a bulk order?

Request a suitable sample, document the baseline and run repeatable production tests that measure quality and total cost.

Explore More Technical Resources

For related manufacturing insights, visit the Kovicrea Technical Insights center. To review available formulations and discuss a trial for your resin and process, explore our sodium sulfate filler masterbatch products.