Quantification of Chemical Composition Distribution of Polyolefin Materials for Improved Accuracy and Speed

Abstract

Crystallization-based separation techniques are widely used for chemical composition distribution (CCD, also often referred as short chain branching distribution SCBD) measurement in the polyolefin industry, in which CCD is among the most critical structural parameters to define their properties and applications. The desire to improve the sample throughput rate by shortening the analysis time in the current CCD techniques would normally sacrifice measurement accuracy due to the cocrystallization phenomena, in which the polymer chains with similar molecular architectures will cocrystallize or coelute enigmatically in the CCD analysis. Herein, we reported the investigation by exploring various separation packing materials on the cocrystallization phenomena. In comparison with the commercially available Crystallization Elution Fractionation (CEF) technique, an improved technique for CCD measurement (iCCD) was developed using the columns packed with gold-coated nickel substrate or spherical gold particles with or without the dynamic cooling process. With iCCD, it was observed with equivalent cocrystallization degree to the industrial gold standard benchmark Wild-TREF method but with over 70+ times improved sample throughput rate (62 vs 4500 min). The experimental CCD chromatogram for a polyolefin blend similarly assembled to the mathematically constructed result further demonstrated the minimized cocrystallization and measurement accuracy in the iCCD method. In addition, the superior mechanical properties of gold-coated nickel particles enabled the long-term robustness and enhanced measurement precision of the iCCD technique during the repeated thermal treatment cycles and pressure variations.

Using Probability Models to Design the Microstructure of Linear Olefin Block Copolymers

“…The molecular weight distribution (MWD) and chemical composition distribution (CCD) of ethylene/1-olefin copolymers determine their properties . The MWD is typically quantified by gel permeation chromatography, − while the CCD can be measured by temperature rising elution fractionation, − crystallization elution fractionation, crystallization analysis fractionation, − and high-temperature thermal gradient interaction chromatography. − However, these analytical techniques can only measure the distribution of the 1-olefin fraction in statistical copolymers. They are inadequate to characterize the features of the OBC microstructure such as the distribution of number of blocks in the copolymer population, the distributions of lengths of hard and soft blocks, and the distribution of chains with specific chemical compositions.…”

Influence of the longest ethylene and isotactic propylene sequences on crystallization elution fractionation of ethylene/propylene copolymers

“…Crystallization elution fractionation (CEF) is the newest crystallization-based method developed to measure the CCD of polyolefins. [1][2][3][4][5][6][7] This technique has higher resolution and needs shorter analysis times than those of older methods, such as temperature rising elution fractionation (TREF) [8,9] and crystallization analysis fractionation (CRYSTAF). [10][11][12] CEF combines the separation power of dynamic crystallization with TREF separation.…”