Comparison of Constant Ratio and Constant Composition Gas Feeding Modes in Olefin Gas-Phase Copolymerization

The impact of constant ratio and constant composition gas feeding modes on the gas-phase copolymerization during preparation of polypropene in-reactor alloy was investigated. The polymerization behaviors under these two modes were compared by analyzing the molecular weight distribution, sequence structure distribution, thermal properties, and mechanical properties of the resulting polymers. It was found that the constant composition feeding mode effectively eliminated the copolymer composition drift, resulted in a narrower lamellar thickness distribution of the gas-phase products, and improved the polymer's toughness and elongation at break. Additionally, solvent fractionation results revealed that samples prepared under constant composition feeding had a higher mass fraction of Fraction B, which further enhanced the material’s toughness. These findings provide theoretical insights for optimizing gas feeding strategies in industrial production to enhance polymer product quality and performance.