Polyethylene formulations with improved barrier and environmental stress crack resistance
Polyethylene formulations and articles produced therefrom, comprise a multimodal high density polyethylene (HDPE) composition, and 0.1 ppm to 300 ppm of a nucleating agent, wherein the multimodal HDPE composition comprises a density of 0.940 g/cm 3 to 0.970 g/cm 3 when measured according to ASTM D792, and a melt index (I2) of 0.1 g/10 min. to 10.0 g/10 min. when measured according to ASTM D1238 at 190° C. and a 2.16 kg load, and wherein the multimodal HDPE composition comprises an infrared cumulative detector fraction (CDF IR ) of greater than 0.27 and an infrared cumulative detector fraction to light scattering cumulative detector fraction ratio (CDF IR /CDF LS ) from 0.7 to 2.0.
1. A polyethylene formulation comprising:
a bimodal high density polyethylene (HDPE) composition, and 0.1 ppm to 300 ppm of a nucleating agent,
wherein the bimodal HDPE composition comprises a density of 0.940 g/cm 3 to 0.970 g/cm 3 when measured according to ASTM D792, and a melt index (I 2 ) of 0.1 g/10 min. to 10.0 g/10 min. when measured according to ASTM D1238 at 190° C. and a 2.16 kg load,
wherein the bimodal HDPE composition comprises an infrared cumulative detector fraction (CDF IR ) of greater than 0.27 and an infrared cumulative detector fraction to light scattering cumulative detector fraction ratio (CDF IR /CDF LS ) from 0.7 to 1.1,
wherein the CDF IR is computed by measuring the area fraction of an IR5 measurement channel (IR) detector chromatogram less than 15,000 g/mol molecular weight using Gel Permeation Chromatography (GPC); and
wherein the CDF LS is computed by measuring the area fraction of a low angle light scattering (LALLS) detector chromatogram greater than 1,000,000 g/mol molecular weight using GPC.
2. The polyethylene formulation of claim 1 , wherein the bimodal HDPE composition comprises a first ethylene polymer component and a second ethylene polymer component, wherein the first ethylene polymer component has a higher density than the second ethylene polymer component as determined from the following equation:
1
overall
.
density
.
=
weight
.
fraction
.
of
.1
st
.
ethylene
.
component
density
.
of
.1
st
.
ethylene
.
component
+
weight
.
fraction
.
of
.2
nd
.
ethylene
.
component
density
.
of
.2
nd
.
ethylene
.
component
and wherein the first ethylene polymer component has a lower weight-average molecular weight than the second ethylene polymer component according to GPC.
3. The polyethylene formulation of claim 2 , wherein the bimodal HDPE composition comprises 40 wt. % to 80 wt. % of the first ethylene polymer component, and 20 wt. % to 60 wt. % of the second ethylene polymer component.
4. The polyethylene formulation of claim 1 , wherein the nucleating agent comprises an organic nucleating agent.
5. The polyethylene formulation of claim 1 , wherein the nucleating agent comprises metal carboxylates, metal aromatic carboxylate, hexahydrophthalic acid metal salts, stearates, organic phosphates, bisamides, sorbitols, or mixtures thereof.
6. The polyethylene formulation of claim 1 , wherein the I 2 is from 0.5 g/10 min. to 5.0 g/10 min and the density is from 0.950 g/cm 3 to 0.960 g/cm 3 .
7. The polyethylene formulation of claim 1 comprising 10 ppm to 300 ppm of a nucleating agent.
8. The polyethylene formulation of claim 1 comprising 10 ppm to 150 ppm of a nucleating agent.
9. The polyethylene formulation of claim 1 comprising 0.1 ppm to 75 ppm of a nucleating agent.
10. The polyethylene formulation of claim 1 , wherein 75 parts per million (ppm) of the nucleating agent increases the crystallization temperature (T c ) of the polyethylene formulation by at least about 1.0° C. as measured according to differential scanning calorimetry (DSC).
11. An article produced from the polyethylene formulation of claim 1 , wherein the article is a molded article or fabricated article.
12. The article of claim 11 , wherein the article provides an oxygen transmission rate improvement of at least about 15% when compared to similar articles that do not comprise the nucleating agent.
13. The article of claim 11 , wherein the article comprises a closure device.
14. A compression or an injection molded article comprising the polyethylene formulation of claim 1 .
15. The polyethylene formulation of claim 1 , wherein the I 2 is from 0.5 g/10 min. to 10.0 g/10 min.
16. The polyethylene formulation of claim 1 , wherein the I 2 is from 1 g/10 min. to 5.0 g/10 min.
17. The polyethylene formulation of claim 1 , wherein the CDF IR is at least 0.30.
18. The polyethylene formulation of claim 1 , wherein the CDF IR is at least 0.32.