1.1 This test method covers the determination of molecular weight distributions and molecular weight averages of polyolefins by high temperature gel permeation chromatography (GPC). This test method uses commercially available polystyrene standards and equipment and is applicable to polyethylenes (excluding high pressure low density polyethylene (LDPE) and ultra-high molecular weight polyethylene (UHMWPE)) and polypropylenes soluble in 1,2,4-trichlorobenzene (TCB) at 140°C. This test method is not absolute and requires calibration.