Composites of polyethylene and polylactic acid

1. Piping comprising:

a composite of polylactic acid and polyethylene, wherein the polyethylene has a tensile strength at yield of from about 3000 psi to 4000 psi, as measured by ASTM-D-638, Type IV Specimen, a tensile modulus of less than about 940 MPa, as measured in accordance with ASTM-D-638, an Izod impact, notched, ranging from about 2.0 to about 20 ft-lb/in, as measured in accordance with ASTM-D-256, and a PENT of less than about 300 hours, as measured by ASTM-F-1473, wherein the composite exhibits a PENT, measured in accordance with ASTM-F-1473, that is at least about 10 percent greater than a PENT of the polyethylene without the polylactic acid.

2. The piping of claim 1 , wherein the composite exhibits a PENT, measured in accordance with ASTM-F-1473, of greater than about 300 hours.

3. The piping of claim 1 , wherein the composite exhibits the tensile modulus, determined in accordance with ASTM D638, that is at least about 2 percent greater than the tensile modulus of the polyethylene.

4. The piping of claim 1 , wherein the composite exhibits a tensile modulus of greater than 940 MPa, determined in accordance with ASTM D638.

5. The piping of claim 1 , wherein the extruded article is an extruded pipe.

6. The piping of claim 1 , wherein the composite further comprises a compatibilizer.

7. The extruded article of claim 6 , wherein the compatibilizer is a functionalized polyolefin.

8. The extruded article of claim 7 , wherein the functionalized polyolefin contains maleic anhydride groups or epoxide groups.

9. The piping of claim 6 , wherein the compatibilizer is an ethylene acrylate terpolymer.

10. The piping of claim 6 , wherein the compatibilizer is present in the composite in an amount ranging from about 1 weight percent to about 5 weight percent, based on a total weight of the composite.

11. The piping of claim 1 , wherein the polyethylene is present in the composite in an amount ranging from about 80 weight percent to about 98 weight percent, based on a total weight of the composite.

12. The piping of claim 1 , wherein the polylactic acid is present in the composite in an amount ranging from about 1 weight percent to about 20 weight percent, based on a total weight of the composite.

13. The piping of claim 1 , wherein the polyethylene is a a metallocene catalyzed polyethylene, or a Ziegler-Natta catalyzed polyethylene.

14. The piping of claim 1 , wherein the composite exhibits an increased ESCR over the polyethylene.

15. The piping of claim 8 , wherein the compatibilizer is polyethylene co-glycidyl methacrylate or glycidyl methacrylate grafted polypropylene.

16. The piping of claim 6 , wherein the compabilitizer is formed in-situ from a reactive modifier.

17. The piping of claim 16 , wherein the reactive modifier is an oxazoline-grafted polyolefin, maleated polyolefin-based ionomers, isocyanate (NCO)-functionalized polyolefins or a combination thereof.

18. The piping of claim 17 , wherein the reactive modifier is a polyolefin grafted with a 2-vinyl-2-oxazoline, 2-fatty-alkyl-2-oxazoline, ricinoloxazoline maleinate, undecyl-2-oxazoline, soya-2-oxazoline, ricinus-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4,4-dimethyl-2-oxazoline or combinations thereof.

19. The piping of claim 18 , wherein the reactive modifier comprises between about 0.1 wt. % to about 10 wt. % oxazoline.

20. The piping of claim 17 , wherein the reactive modifier is a polyolefin grafted with an isocyanate functional monomer.

21. The piping of claim 17 , wherein the reactive modifier is a polyolefin ionomer maleated and then neutralized with a metal component.

22. The piping of claim 16 , wherein the reactive modifier includes from about 95 wt. % to about 99 wt. % polyolefin based on the total weight of the reactive modifier.

23. The piping of claim 16 , wherein the composite consists of the polyethylene, polylactic acid, and the compatibilizer.