Relationships between molecular weight, solution viscosity, and melt index for narrow distribution, high pressure polyethylene whole polymers. Fast M̄_n determinations

Melt and solution viscosity properties of laboratory-prepared batch polymerized high pressure polyethylene have been found to correlate well with molecular weight. These polymers have narrow and nearly constant molecular weight distributions and contain essentially no long-chain branches. Short-chain branching was found to have little or no effect on the relationships. Polyethylene made in the same reactor having long-chain branches had melt and solution viscosity properties which deviated seriously from these relationships. The deviations serve as a semiquantitative measure of long-chain branching. When long-chain branching is absent, the correlations serve as rapid methods of determining M̄_n for narrow-distribution polymers.