Bimodal HDPE

Melt Rheology

Shear sensitivity dictates processing behaviour across varied extrusion rates and injection pressures. Long relaxation times characterising the high-molecular-weight component cause melt fracture during high-speed tube production if die gap temperatures drop below critical thresholds. Viscosity drops sharply under the high shear rates experienced within screw channels, allowing throughput increases without exceeding motor load limits.

Pressure oscillations inside the barrel indicate improper temperature profiles that degrade the balance between the two molecular populations.

Resin Economy

Virgin polymer pricing reflects the dual-reactor technology required to maintain precise comonomer incorporation in the high-density fraction. Regrind introduction alters stress crack performance because thermal history during initial moulding preferentially degrades the high-molecular-weight chains first. Mixing virgin pellets with recycled flakes exceeding twenty percent mass fractions requires readjusting clamp tonnage to compensate for altered crystallinity.

Part specifications dictate allowable regrind percentages to prevent premature failure under sustained internal pressure testing.

Shrinkage Control

Volumetric contraction during cooling depends directly on crystallinity development inside the mould cavity. Part dimensions deviate from datasheet values when coolant temperature fluctuations alter spherulite growth rates across thick wall sections. Holding pressure profiles must compensate for rapid volume reduction as the material transitions from liquid to solid state.

Warp formation occurs when differential cooling rates between core and cavity surfaces induce internal residual stresses.