Effect of Calcium Carbonate Properties on the Reinforcement of HMW-HDPE Film, 1999 Polymers, Laminations & Coatings Conference Proceedings

F. A. Ruiz--LLDPE-based pelleted concentrates were used to add 0, 7.5%, & 15wt.% of different fine-ground, surface-treated calcium carbonate (CaCO3) minerals to a high-molecular weight HDPE film resin. These dry blends were extruded into film on a 50mm, 18/1 L/D grooved-feed extruder fitted with a 100mm (4”) die and 0.9mm (0.036”) die gap. Neck height and blow-up ratios (BUR) also were varied to determine how the addition of CaCO3 affected film property response to variation in these process conditions.

Mineral addition yielded output rate increases of 5% at 7.5% CaCO3 and 10% at 15% CaCO3 while simultaneously decreasing melt pressure and motor load (current). Depending upon calcium carbonate grade, mineral loading, and processing conditions, increases in dart impact strength and/or tensile yield stiffness were achieved. Calcium carbonate mineral grades also exhibited differences in the level of extrusion and bubble stability. Mineral reinforcement of HMW-HDPE films increases film coefficient of friction, which improves stacking of liners or merchandise bags.