Molecular Structure of Metallocene-Catalyzed Polyethylene:  Rheologically Relevant Representation of Branching Architecture in Single Catalyst and Blended Systems

Abstract

The goal of this work was to provide a usable framework for describing the molecular structure of long-chain branched, metallocene-catalyzed polyethylene (mPE). This will allow better understanding of structure-property relations for these materials and in the future allow the development of new metallocene based systems with tailor-made properties. In particular, we are interested in the relationship between molecular structure and rheological behavior of polyethylene and therefore represent the structure in terms that are relevant to the rheological properties. To provide an intuitive understanding of the structure, we present a ternary diagram showing clearly the independent variables in the system and allowing a quick analysis of blended systems.

Correlations between the Shape of Viscosity Functions and the Molecular Structure of Long‐Chain Branched Polyethylenes

“…Previously this was only possible for linear samples. [1] The findings that l 2 scales with M w in the same way as l (or v C À1 ) in linear polymers, [1] clearly shows that the curvature in the viscosity function, to which l 2 is assigned, is indeed caused by linear chains making up typically about 50%, [37] and, thus, l ( …”

“…From these relationships and dependencies, it does not seem unrealistic to conclude that l 1 reflects the influence of the long-chain branches, whereas l 2 is mainly influenced by the linear molecules. As LCB-mPE is a mixture of star and linear chains (and very few higherbranched chains), [36,37] the higher exponent of the power law linking l 1 and M w , in comparison to l 2 and M w , is the direct consequence of the dependence linking the characteristic relaxation time (and, thus, the zero shear-rate viscosity h 0 ) and the molar mass of stars. [38] Correlation between the Slope n and the Zero-ShearRate Viscosity Enhancement Factor h 0 =h lin 0…”

Large amplitude oscillatory shear and Fourier transform rheology analysis of branched polymer melts

“…Further details of these practices can be found in, for example Peacock (2000). These materials have been investigated and well characterized in previous studies, e.g., Costeux et al (2002), Das et al (2006), Hassell et al (2008), and Hoyle et al (2009Hoyle et al ( , 2013.…”

Structure and rheology of branched polyamide 6 polymers from their reaction recipe

“…Some works have already been proposed in this direction for metallocene polyethylene [25][26][27] as well as for polydisperse polyamide samples. [28][29][30][31][32] In the latter case, it has been shown that classical Monte Carlo statistics lead to a good approximation of the sample, which is formed by a condensation reaction process.…”