Monitoring the chemical heterogeneity of metallocenecatalysed copolymers of ethylene and higher 1-olefins using CRYSTAF and SEC-FTIR

Abstract

Copolymers of ethylene with 1-decene, 1-tetradecene and 1-octadecene were prepared using the catalyst system racEt[Ind]2ZrCl2/MAO and were analysed with regard to chemical heterogeneity using crystallisation analysis fractionation (CRYSTAF), differential scanning calorimetry (DSC) and size exclusion chromatography coupled to FTIR (SEC-FTIR). The melting and crystallisation temperatures from DSC decrease linearly with increasing amount of comonomer, independently of the nature thereof. The decrease in crystallisation temperature from CRYSTAF of copolymers with higher 1-olefin content indicates a small dependence on the length of the side chain. The chemical heterogeneity of the copolymers as analysed by DSC and CRYSTAF broadens with increasing comonomer concentration.

Characterization of ethylene‐propylene copolymers with high‐temperature gradient adsorption liquid chromatography and CRYSTAF

“…[4][5][6][7][8][9][10][11] The average chemical composition is determined mainly using FTIR or NMR spectroscopy. However, SEC separation may be combined with the on-line FTIR [12][13][14] or NMR 15 spectroscopic analysis. In such cases, information about the distribution of the chemical composition along the molar mass axis is obtained.…”

Advanced Separation Techniques for Polyolefins

“…Recently, the use of a graphitic stationary phase (Hypercarb) for the separation of PP according to tacticity was reported [38]. This technique enables the generation of 2D characterization data for virtually any polyolefin over a wide compositional range regardless of crystallinity [46][47][48][49]. The fast and efficient separation of polyolefins and olefin copolymers with respect to chemical composition in a short time can only be achieved by the above method [39][40][41][42][43][44].…”

“…In this case, the analysis relies on the measurement of the absorption bands of the backbone methylene groups (at 2,855 cm À1 and 2,926 cm À1 ) corresponding to the total concentration and the methyl groups (at 2,874 cm À1 and 2,957 cm À1 ) corresponding to the concentration of the comonomer [48,49]. In this case, the analysis relies on the measurement of the absorption bands of the backbone methylene groups (at 2,855 cm À1 and 2,926 cm À1 ) corresponding to the total concentration and the methyl groups (at 2,874 cm À1 and 2,957 cm À1 ) corresponding to the concentration of the comonomer [48,49].…”

Separation of bimodal high density polyethylene using multidimensional high temperature liquid chromatography

“…Temperature Rising Elution Fractionation (TREF) [17][18][19][20], Crystallization Analysis Fractionation (CRYSTAF) [21,[24][25][26][27][28][29][30][31][32][33][34][35][36][37], and Crystallization Elution Fractionation (CEF) [22] have been developed with the aim to deformulate semi-crystalline olefin copolymers according to their chemical composition. These techniques are based on the crystallization of macromolecules from a hot dilute solution in a temperature gradient.…”