Scientific publications

Search abstracts of Borealis' scientific publications. To download pdf versions of Borealis' brochures, case studies, articles, summary data sheets, product news and presentations, please search our literature library.

Authors:	Year:	Key words:

Page: 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

Title	Year
Effect of ethylaluminum dichloride on controlling high molecular weight tail of polyethylene made with SiO2-supported Ziegler-Natta catalyst system. 2002, Kyung-Jun Chu, Thomas Garoff, Päivi Waldvogel, Kari Pesonen. Effect of ethylaluminum dichloride on controlling high molecular weight tail of polyethylene made with SiO2-supported Ziegler-Natta catalyst system. 1st BlueSky Conference on Catalytic Olefin Polymerization, Sorrento, Italy, 17.-20.06., 2002 Poster. Ethylene polymerisation was carried out with SiO2-supported Ziegler-Natta catalysts (E16, E20, E24 and E28) prepared with different amounts of ethyl aluminium dichloride (EADC). The investigation through Ti oxidation state and elemental compositional measurements indicated that addition of EADC resulted in changes of the fraction of Ti oxidation states from Ti4+ to the lower oxidation states and increase of aluminium and chlorine amounts in the catalysts. As EADC increased in the catalyst preparation step, it was found that molecular weight of the produced polyethylene increased and molecular weight distribution was broadened. Deconvolution of the molecular weight distribution with Flory's most probable function showed the presence of multiple active site types for the catalysts prepared in this study. Additionally, it showed that increasing of EADC led to increase of the high molecular weight fraction and creating one more active site giving high molecular tail in the presence of large amount of EADC. This may indicate that Ti oxidation state and chemical composition of the catalyst are key parameters to tailor high molecular weight tail for Ti-based heterogeneous Ziegler-Natta catalyst systems. printme	2002
PP model compounds as tools for the development of high-impact copolymers 2002, Andreas Hauer, Klaus Bernreitner, Elisabeth Ingolic, Markus Gahleitner. PP model compounds as tools for the development of high-impact copolymers Proc. of 18th International PPS Conference, Guimaraes, 2002 The development of heterophasic PP-copolymers, which are necessary in many applications because of their property profile, requires large capacities in pilot plants for a systematic variation of the properties. A possible alternative are model compounds, where the different components are blended in an extruder. The possibility to evaluate three main influence factors on mechanics of such systems, namely the viscosity ratio between matrix and elastomer phase, the phase compatibility and the composition of the elastomer phase, is demonstrated in a series of investigations. Morphology investigations based on transmission electron micrographs have proven to be an indispensable tool for obtaining systematic information from such blend systems, which can be further used for the development of reactor-based systems. printme	2002
Molecular structure and nucleation effects on shear-induced crystallization in polypropylene 2002, Markus Gahleitner, Johannes Wolfschwenger, Christian Paulik, Wolfgang Neißl. Molecular structure and nucleation effects on shear-induced crystallization in polypropylene Proc. of 18th International PPS Conference, Guimaraes, 2002 External nucleation systems, frequently used to improve the properties of polypropylene, produce a significantly different combination of external properties (shrinkage, anisotropy, mechanics, optics), the reasons for which are not always well-known. There are several possible sources for these differences, one of which is the polymorphic nature of polypropylene. Another important factor is the development of shear-induced superstructures, which is affected both by the molecular structure of the polymer (molecular weight distribution, isotacticity and comonomer incorporation) and by the type of nucleating agent. In several studies the interaction between the type of nucleating agent and base polymer was investigated in terms of morphology and end-use properties. Qualitative to semi-quantitative correlations resulting from these studies are presented. Depending on the application in question and the desired property improvements, "ideal" combinations of nucleant and polymer have to be found printme	2002
Decrease in activity caused by hydrogen in Ziegler-Natta ethene polymerisation 2002, Thomas Garoff, Solveig Johansson, Daniel Lindgren, Kari Pesonen, Päivi Waldvogel. Decrease in activity caused by hydrogen in Ziegler-Natta ethene polymerisation Eur. Polym. J., 38, 2002, 121-132 In this study we prepared seven different ZieglerNatta catalysts and polymerised them at different hydrogen concentrations in order to investigate their kinetic behaviour during polymerisation. The objective was to see whether the results corresponded to what could be expected on the basis of Kissin's beta-agostic deactivation theory. According to this theory, hydrogen causes the formation of dormant sites due to the formation of beta-agostic coordination from the ethyl groups formed after hydrogen termination. According to this theory, the more hydrogen that is used, the more beta-agostic coupling and the smaller percentage of Ti in a polymerising state. This beta-agostic coupling would thus explain the lower activity level seen in polymerisation where more hydrogen has been used. The results of this study showed that none of the catalysts showed the kind of behaviour that would correspond to what could be predicted on the basis of Kissin's theory. Deactivation could be detected only when a lower amount of hydrogen was used. When higher amounts of hydrogen were used in polymerisation there was a clear delay in activation time of the catalysts. This particularly seemed to be the case for catalysts where Ti was present as Ti(IV). This delay in the activation of the catalyst caused a decrease in activity in addition to the normal decrease in activity due to hydrogen replacing C2 in the polymerisation process. The only catalyst showing no delay in activation was a silica-based PE ZN catalyst where the Ti was already in trivalent form. In this case no decrease in activity was observed in addition to the normal decrease in activity caused by hydrogen replacing C2 in the polymerisation process. printme	2002
Advanced Polyethylene Products Utilising Single Site Catalysts Designed for the Borstar PE Process 2002, Hans Eklind. Advanced Polyethylene Products Utilising Single Site Catalysts Designed for the Borstar PE Process MetCon 2002, Houston 06.06., 2002 The bimodal Borstar PE process was developed by Borealis to meet the increasing property demands for polyethylene products. The first commercial plant started in 1995. The success of Borstar PE technology is built on three closely interlinked factors: The production process, the catalyst and the large variety of high performance products. The combination of a slurry loop reactor and a gas phase reactor, and employing a special Ziegler catalyst technology, enable manufacturing of well processable LLDPE, MDPE and HDPE resins, which have been brought successfully to the market. The fundamental idea of making a bimodal polymer is that the molecular weight distribution and comonomer distribution can be controlled independently. This is for instance enabling us to make bimodal butene-LLDPE film resins exhibiting LDPE processability combined with the mechanical properties of unimodal octene-LLDPE. Borealis is currently developing new single site catalyst systems to be implemented in the Borstar PE process. This development stems from a decade of Borealis activity in research, scale-up and commercialisation of single site catalysts. The composition and thus properties of the resulting products will be very different from existing conventional polyethylene or narrow single site polyethylene resins. By combining the favourable processability of bimodal Borstar PE products with the more homogeneous molecular weight and comonomer incorporation offered by single site catalyst technology, product properties can be tailored better and more broadly than ever before. As an example, bimodal single site LLDPE film resins having an excellent balance of processability, mechanical as well as optical properties has recently been demonstrated in pilot scale. The first commercial production is planned to start in a near future printme	2002
Reaction Modelling of Single Site Catalysts 2002, Erling Rytter, Kjell-Arne Solli, Jon Andreas Støvneng. Reaction Modelling of Single Site Catalysts 1st Blue Sky Conference on Catalytic Olefin Polymerization, Sorrento, Italia, 17-20 June, 2002 Poster. A family of zirconocenes having various ligand substitutions and bridge structures, has been explored with respect to ethylene polymerisation and co-polymerisation. Possible reaction mechanisms have been searched for by theoretical calculations, and structure parameters have been investigated in order to control co-monomer incorporation. The theoretical study has been supported by experimental work. The reaction pathways for propagation and chain termination reactions have been explored by quantum mechanical calculations applying the density functional theory (DFT). For ethylene homopolymerisation, it was found at least three likely propagation reaction pathways including the beta-agostic and gamma-agostic chain conformations, as well as three more or less likely chain termination reaction pathways. The structure of the zirconocene greatly influenced the importance of the individual reaction pathways. This reaction scheme could explain the relative occurrence of vinylic chain ends found in experimental work. The structure of the zirconocene also greatly influenced to which degree a co-monomer was likely to be incorporated during chain propagation. A few structural parameters were identified, which could substantially depress co-monomer incorporation without too much loss of catalytic activity for ethylene polymerisation. More than 20 zirconocene structures were explored, and half of them was tested experimentally. printme	2002
On-line kvalitetsanalyse in Borealis 2002, Rune Mathisen, Kristian Helland. On-line kvalitetsanalyse in Borealis Norwegian Chemimetrics Society, 14. Symposium on Chemometrics, Gol 13. March, 2002 printme	2002
Reactivation of a Poisoned Metallocene Catalyst by Irradiation with Visible Light 2002, Karl-Heinz Reichert, Anette Wartmann, Kalle Kallio. Reactivation of a Poisoned Metallocene Catalyst by Irradiation with Visible Light Macromol Rapic Commun, 23, 2002, 187-190 Both oxygen and carbon dioxide are efficient catalyst poisons, remarkably reducing the ethylene polymerisation rate, increasing the molecular weight of the resulting polyethylene, and broadening its molecular weight distribution (MWD). By introducing visible light into the contaminated polymerisation system, the catalyst activity was totally recovered. The molecular weight and MWD became similar to those of a non-poisoned system, supporting the formation of new active sites during poisoning that are responsible for the lower activity and broader MWD. printme	2002
Extensional Creep Rheometry 2002, Reinhard Forstner, Hermann Janeschitz-Kriegl, Manfred Stadlbauer, Gerhard Eder. Extensional Creep Rheometry Proc of the 6th European Rheology Conference, Erlangen, DE,, 2002, 477-478 Elongation of polymer melts is one of the most important types of deformation occurring during polymer processing like melt spinning, film and bottle blowing as well as in biaxial stretching of extruded sheets. However, only few practicable extensional rheometers have been developed so far. A new 'spin-line'-type rheometer operating in tensile creep mode is presented, which allows to cover a wide range of temperature, total extension and extension rate. The instrument called 'WINDBIX' has already been tested succesfully on a number of different polymers (linear and branched polyolefins). printme	2002
Orientation effects on the rheological behavior of polypropylene/clay nanocomposites 2002, Markus Gahleitner, Kshama Motha, Esa Vuorihuhta, Elisabeth Ingolic, Bernhard Knogler. Orientation effects on the rheological behavior of polypropylene/clay nanocomposites Proc. of the 6th European Rheology Conference, Erlangen, DE, 2002, 623-624 Similar to other multiphase polymer systems (like polymer blends or mineral-filled composites), also nanocomposites consiting of polypropylene and organically modified clay nanoparticles have been found to exhibit a strong sensitivity of their linear-viscoelastic behaviour to pre-shearing. Two differently prepared systems were investigated in comparison to compounds with conventional micro-particiulate fillers in terms of shearing effect and subsequent structural relaxation. The multi-frequency technique on a rotational rheometer was used for these studies, taking other problems like sample deformation and nonlinearity into account. A full characterisation of the samples before and after investigation, including transmission electron microscopy for resolving the structural changes, supplemented the rheological measurements printme	2002