The molecular structure of polyethylene. XII. Intrinsic viscosities of polyethylene solutions

While the intrinsic viscosity of polyethylene solutions is reported in the literature for at least 6 different solvents and 14 different temperatures in 23 combinations, few relations exist for converting from one set of conditions to another. Likewise, intrinsic viscosity–molecular weight relations are reported for several sets of conditions and polymer types, in some cases leading to inappropriate comparisons. The following relations are established between the intrinsic viscosities of branched polyethylene in different solvents: where α denotes α‐chloronaphthalene at 125°C. d, decahydronaphthalene at 70°C.; t, tetrahydronaphthalene at 125°C.; and x, p ‐xylene at 85°C. The relations for linear polyethylene are significantly different from those for branched polyethylene, but have not been established in detail. The literature is examined for the appropriateness and reliability of intrinsic viscosity–molecular weight relationships for polyethylene. Analysis of the experimental data leads to the following relations for linear polyethylene which are proposed as the most consistent, reliable, and appropriate currently obtainable (in‐trinsic viscosities are expressed in deciliters/gram for measurement conditions of decahydronaphthalene at 135°C., within experimental error of those specified in ASTM D 1601–58T). For the number‐average molecular weight of fractions of linear polyethylene, [η] = 2.3 × 10 −4 M n 0.82 ; for the weight‐average molecular weight of whole polymer samples of linear polyethylene, [η] = 2.55 × 10 −4 M w 0.74 ; for the weight‐average molecular weight of fractions of linear polyethylene, [η] = 3.9 × 10 −4 M w 0.74