According to one embodiment, a process for producing a unimodal ethylene/-olefin copolymer, the process comprising contacting ethylene and one or more (C.sub.3-C.sub.12) -olefin comonomers with a chromium-based catalyst system in a gas-phase polymerization reactor to produce the unimodal ethylene/-olefin copolymer; wherein the unimodal ethylene/-olefin copolymer comprises: a density from 0.952 g/cm.sup.3 to 0.957 g/cm.sup.3; a flow index (I.sub.21) from 4.0 to 6.2 dg/min; a melt viscosity ratio (V.sub.0.1/V.sub.100) at 190 C. of 55 to 75; a molecular weight distribution (MWD) as calculated by the weight average molecular weight (M.sub.w) divided by the number-average molecular weight (M.sub.n) (M.sub.w/M.sub.n); and a peak molecular weight (M.sub.p), all as measured by gel permeation chromatography.