How to run an antiblock trial on blown polyethylene film

In short: Compound the candidate antiblock into a masterbatch on your own extruder, let it down into film at the same level as the incumbent on the same line settings, and measure blocking, haze, gloss and coefficient of friction on conditioned film. Sensilchem starts film trials with CENSIL 773 for clear packaging and 779 where appearance is tighter, with 185P as the conventional comparison.

What you need

  • Your film resin and the incumbent antiblock masterbatch
  • Candidate sample set: 773 or 779, plus 185P as comparison
  • Twin-screw compounder for the masterbatch, blown film line, slitter
  • Blocking tester, haze meter, gloss meter, COF tester and a conditioning room

Step by step

  1. Make the masterbatch on your own compounder

    Compound each candidate at the same loading into the same carrier resin, with the same screw profile and temperature. Screen-pack pressure during compounding is the first dispersion result; log it.

  2. Let down at the incumbent level

    Run the film at the same antiblock level as the incumbent, on the same die gap, blow-up ratio and output. Change nothing on the line between samples except the masterbatch.

  3. Check for specks before measuring anything

    Inspect the film bubble and the wound roll for specks and gels. A grade that measures well but shows specks at the customer's inspection station has failed.

  4. Condition the film before testing

    Let the rolls condition in the standard climate for at least a day. Blocking and COF measured on warm, fresh film do not represent the roll the customer opens.

  5. Measure blocking, haze, gloss and COF together

    Report all four for every sample in one table with the incumbent in the first column. Antiblock is a balance, and a grade that wins on blocking and loses on haze is only half a result.

  6. Age a roll under load

    Keep one wound roll under stacking load in a warm room for a week and re-test blocking from the inside wraps. That is where block failures appear in the warehouse.

Mistakes that spoil the comparison

  • Comparing candidates at different loadings.
  • Measuring haze on the bubble line by eye instead of on conditioned film.
  • Ignoring screen-pack pressure during compounding.

Questions we get asked

Low-iron grades — why does it matter?

Iron in the silica shows up as a faint colour in clear film and as a yellowness value the packaging buyer can measure. The low-iron platform (773 and 779) exists for optics, the conventional grade for cost.

Can the trial be done on cast film?

Yes. The steps are the same; conditioning and the blocking test under load are still the ones that decide the outcome.

Tell us what is failing in the process

The material you use now, the formulation or resin, the equipment and the target you need to hit. That is enough for us to say whether we have something worth testing.

Request a sample Contact us
Application & sales Ms. Nina Zhang nina@sensilchem.com +86 597-2200392
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