SIZES OF LONG BRANCHES IN LOW-DENSITY POLYETHYLENES

**1**3C-NMR spectroscopy and size exclusion chromatography have been used to determine the mean length of long branches in a number of high pressure process low density polyethylenes (LDPEs). **1**3C-NMR analyses count all branches longer than C5 as 'long'. The polyethylenes studied had 2-3 long branches per 100 carbons. The mean branch length was of the order of 200-300 carbons in length. The size of long branches increases with M OVER BAR //n of the parent polyethylene, but the size of long branches relative to the overall macromolecular size decreases with increasing M OVER BAR //n. The mean molecular weight of the long branches is some 5-20% of M OVER BAR //n of the particular polymer and decreases as M OVER BAR //n increases. Both autoclave and tubular reactor products were studied.