POLYETHYLENE COMPOSITION HAVING HIGH SWELL RATIO

摘要

Polyethylene composition with improved swell ratio and mechanical properties, particularly suited for preparing blow-moulded articles, said composition having the following features:;1) density from 0.952 to 0.960 g/cm3;

2) ratio MIF/MIP from 17 to 30;

3) Shear-Induced Crystallization Index SIC from 2.5 to 5.0.

主权项

1. A polyethylene composition having:
1) a density from 0.952 to 0.960 g/cm3, determined according to ISO 1183 at 23° C.; 2) a ratio MIF/MIP from 17 to 30, wherein the MIF is the melt flow index at 190° C. with a load of 21.60 kg, and the MIP is the melt flow index at 190° C. with a load of 5 kg, both determined according to ISO 1133; 3) a SIC Index from 2.5 to 5.0; wherein the SIC Index is the Shear-Induced Crystallization Index, determined according to the following relation:
SIC Index=(tonset,SIC@1000×tonset,quiescent)/(HLMI)where tonset,SIC@1000 is measured in seconds and is the time required for crystallization onset under shear rate of 1000 s−1, the tonset, quiescent is measured in seconds and is the crystallization onset time at temperature of 125° C. under no shear, determined in isothermal mode by differential scanning calorimetry; HLMI is the melt flow index determined at 190° C. with a load of 21.6 kg, according to ISO 1133.