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Abstract

Anti-block agents differing in composition, structure, and surface coating were compounded with fluorocarbon elastomer polymer processing aids (PPAs) in linear low density polyethylene. Separate and combined masterbatches of 20% anti-block and 2% PPA were melt mixed and let down to 5000 ppm and 500 ppm respectively.

Preliminary investigation of the combined PPA/anti-block masterbatches by capil lary rheometer identified wide ranging differences when comparing equilibrium melt viscosity and melt fracture onset. Synthetic silicas appeared to show the great est decrease in PPA performance while ceramic micro-spheres caused little change. Further studies were conducted on a commercial film line at shear rates of 750 s^-1. Results showed that the PPA was generally more effective when incorporated as a separate masterbatch than when compounded with the anti-block. For example, melt fracture could only be eliminated in the presence of diatomaceous earth and the PPA when the two were compounded separately. In the case of calcium carbonate and ceramic spheres, melt fracture was eliminated in the combined samples but equilib rium pressures were higher and equilibrium times were longer. Coated silicas showed less interference with PPA performance than did their uncoated analogs when used in a combined masterbatch.

Keywords

anti-block blown film compounding fluorocarbon elastomer inter ference linear low density polyethylene masterbatch melt fracture PPA (polymer processing additive)sharkskin.

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References

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Effects of Anti-Block/Processing Aid Combinations On Lldpe Blown Film Extrusion

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