All Issues
A new method for investigation of short-chain branching distribution in polyethylene by combined use of FTIR and TREF
†
Author : H. Hassani *a, Z. Akbaripanah, R. Rashedi b and N. Feizi
DOWNLOAD PDF
ABSTRACT
Qualitative analysis of short-chain branches was carried out on High-Density Polyethylene by Fourier transform infrared spectroscopy. In this work, the copolymer was fractionated according to chemical composition by preparative temperature rising elution fractionation (TREF), and resulting fractions were submitted to FTIR analyses. Fourier self-deconvolution was used to resolve overlapping bands for ethyl, butyl, and isobutyl branches. An infrared spectrophotometer was calibrated for the quantitative determination of butene-1 in copolymers. In this procedure, using calibration derived from analysis 1, butane-ethylene copolymers of known composition (13C NMR analysis), the following measurements are performed. The FTIR and NMR data are in qualitative and quantitative agreement. The FTIR technique is less costly and faster than NMR spectroscopy. These results were explained by the existence of a heterogeneous distribution of commoner molecules. This method eliminates every personal mistake and enables the FTIR technique to determining short chain branching distribution. According to the results of TREF, low molecular weight fractions at lower temperature and higher molecular weight fractions were isolated at higher temperatures. Also, infrared spectroscopy measurements showed that this technique could separate fractions according to their degree of short chain branching. The low molecular weight segments had more short-chain branching than the higher molecular weight segments.
KEYWORD
High-Density Polyethylene, short-chain branches, fractionation, temperature rising elution fractionation, Fourier transform, infrared