An improved method for the high isotacticity measurement of polybutene-1

Abstract

High isotactic polybutene-1 (HiPB) plays important roles in presenting outstanding resistance to creep and crack at high temperature. Therefore, rapid and accurate measurement of the HiPB is extremely important for both synthesis and application of polybutene-1 (PB). In this work, solvent extraction fractionation with diethyl ether (DE) and n-hexane (C6) as solvents (DE-C6 method) and an improved fractionation method combining isothermal crystallization and solvent extraction with xylene (Xyl) and n-pentane (C5) as solvents (Xyl-C5 method) were used to fractionate PB samples. The carbon-13 nuclear magnetic resonance spectrometry (13C-NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) were used to conduct the composition analysis of PB original samples and PB fractions. It was found that the DE-C6 method was greatly depended on the molecular weight of the fractions, while the Xyl-C5 method was biased on the isotacticity of PB fractions and fractionated PB samples into atactic PB (aPB), medium isotactic PB (MiPB) and HiPB, which showed independence on the molecular weight of fractions. Therefore, the Xyl-C5 method is recommended for more accurate measurement and isolation of HiPB fractions from PB samples.