Formulating calcium carbonate masterbatches

Lucky Radebe, James Wesley-Smith, Walter W. Focke*, Shatish Ramjee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


The effects of filler content, filler particle size and surface coating, as well as the natures of the wax and metal stearate lubricants on the properties of calcium carbonate-filled linear low-density polyethylene compounds were investigated. The elongation at break decreased exponentially with filler loading irrespective of whether the filler was surface coated or not. The corresponding decline in the impact strength was more gradual but it dropped abruptly on reaching a filler loading of 70 wt%. The effect of shear rate on the apparent melt viscosity followed an empirically modified Carreau-Yasuda model which included the effect of filler content. It features the zero-shear viscosity and the flow consistency index as adjustable parameters. These characterize the viscosity trends at low- and high-shear rates, respectively. In the absence of additives, the melt viscosity at 60 wt% filler exceeded that of the neat polymer by a factor of three. Adding 3 wt% wax and 1.0 wt% zinc stearate returned the melt viscosity to levels just above that of the neat polymer. Calcium stearate and magnesium stearate were less effective at reducing the apparent melt viscosity but a blend of the latter with zinc stearate performed particularly well.

Original languageEnglish
Pages (from-to)80-88
Number of pages9
JournalJournal of Polymer Engineering
Issue number1
Publication statusPublished - 1 Jan 2023
Externally publishedYes


  • Fischer-Tropsch wax
  • calcium carbonate
  • masterbatch
  • polyethylene
  • rheology


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