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: 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Title	Year
The influence of nucleus density on optical properties in nucleated isotactic polypropylene 2009, Alfred Menyhard, Markus Gahleitner, Joszef Varga, Klaus Bernreitner, Pirjo Jaaskelainen, Harry Øysæd, Bela Pukanszky. The influence of nucleus density on optical properties in nucleated isotactic polypropylene European Polymer Journal, 45 (-), 2009, 3138–3148 The effect and efficiency of three nucleating agents, a sorbitol based clarifier, a traditional heterogeneous nucleating agent and poly(vinylcyclohexane) (PVCH) was studied in polypropylene (iPP) homopolymer. The nucleating agents were added to iPP in different amounts; PVCH in 0–200 ppm, while the other two in 0–2000 ppm. Optical and mechanical properties were determined on injection molded plates or bars, respectively. Nucleation efficiency was studied by thermal analysis, while structure was characterized by polarized light (PLM), scanning electron (SEM) and atomic force microscopy (AFM). Nucleus density was calculated using the method of Lamberti, which is based on the kinetic theory of the crystallization developed by Lauritzen and Hoffmann. The results proved that the nucleating agents modify properties in different ways and extent. PVCH is very efficient already at small concentrations and increases the stiffness of iPP considerably more than the other two compounds. On the other hand, the clarifier and the traditional nucleating agent induce better optical properties even at smaller efficiency. The structure developing in the presence of the three nucleating agents is also different. The clarifier forms a network in iPP and induces the formation of a microcrystalline structure according to the former literature data. Microspherulitic structure develops in the presence of the heterogeneous nucleating agent studied, while relatively large supermolecular units form in iPP nucleated by PVCH even under the conditions of injection molding. The calculation of nucleus density by existing models and the comparison of the results to optical properties proved that haze is determined by the size of the supermolecular units of the polymer and this latter depends on nucleus density. printme	2009
Joint Effects of Molecular Structure and Processing History on Specific 2009, Lenka Chvatalova, Jana Navratilova, Roman Cermak, Miroslav Raab, Martin Obadal. Joint Effects of Molecular Structure and Processing History on Specific Macromolecules, - (42), 2009, 7413-7417 The interrelation between specific β-nucleation, thermal history, and molecular weight of isotactic polypropylene (PP) has been investigated by wide-angle X-ray scattering, differential scanning calorimetry, and scanning electron microscopy. Samples with a broad range of molecular weight (Mw), from 240 000 to 1 300 000, allowed to examine the effect of PP molecular structure on the nucleation sensitivity. N, N0-Dicyclohexylnaphthalene-2,6-dicarboxamide (NU 100) was introduced in the concentrations of 0, 0.01, and 0.03 wt%as a β-specific nucleating agent into neat PP. Specimens were then processed via compression molding at various processing temperatures and times. Samples containing 0.01 wt % of NU 100 showed a dramatic decrease of nucleation activity into β-phase with increasingMw, processing time, and temperature. This effect was ascribed to a partial solubility of nucleator in PP melt and a competition between heterogeneous β-nucleation and self alpha-nucleation. printme	2009
Poly(norbornene)s as matrix materials for platinum tetrakis(pentafluorophenyl)porphyrin based optical oxygen sensors 2008, Kurt Stubenrauch, Martina Sandholzer, Fabian Niedermair, Kerstin Waich, Torsten Mayr, Ingo Klimant, Gregor Trimmel, Christian Slugovc. Poly(norbornene)s as matrix materials for platinum tetrakis(pentafluorophenyl)porphyrin based optical oxygen sensors European Polymer Journal 44 (2008) , 44 (8), 2008, 2558-2566 A set of poly(norbornenes) was prepared using ring opening metathesis polymerization (ROMP) and used as matrix material for the preparation of optical oxygen sensor layers based on platinum tetrakis(pentafluorophenyl)porphyrin (PtTFPP) as the sensitive dye. Different polymers were prepared and investigated in order to retrieve information on the influence of the anchor group and the side chain attached to the polymer backbone on their performance as matrix material for the dye. Bulky side groups increased the oxygen permeability through ROM polymer layers, especially when the bulky group was directly attached via an anchor group to the polymer backbone without any aliphatic spacer in between. Sensor layers made of poly(endo,exo[2.2.1]bicyclo-5-heptene-2,3-dicarboxyclic acid di-tert-butylester) and PtTFPP exhibited the highest s0/s ratio and responded strongly to small amounts of oxygen. printme	2008
Polymorphic Crystallization of beta-nucleated Polypropylene Pipe Extrusion – Comparison Between Simulation and Experiment 2008, Susanne Nestelberger, Markus Gahleitner, Stefano Piccarolo, Zebene Kiflie, Siegfried Liedauer, Thomas Koch. Polymorphic Crystallization of beta-nucleated Polypropylene Pipe Extrusion – Comparison Between Simulation and Experiment PPS24 – Annual Meeting of the Polymer Processing Society, Salerno, Italy – June 15-19 2008, - (-), 2008, - In order to meet the increasing requirements in new market segments as well as to overcome the growing competition of other materials the polymorphism of PP can be used. Special nucleating agents are added to induce the beta-modification which leads to an improved long term strength and elevated impact resistance of the final product. The present work aims at verifying the assumed influence of processing/cooling conditions on the morphology by simulating the cooling behavior of an extruded pipe with a common FE-program (Abaqus/CAE 6.5) and evaluating the resulting fraction of beta-modification. First comparisons of the simulated values with WAXD-measurements on produced pipes show a qualitatively good agreement. The discussed model is able to display the different behavior at the inner and outer layer of the pipes. Additionally the impact behavior is set into relation with the beta-content and optimized process conditions for beta-nucleated PP are proposed. printme	2008
Porous Versus Novel Compact Ziegler–Natta Catalyst Particles and Their Fragmentation During the Early Stages of Bulk Propylene Polymerization 2008, Torvald Vestberg, Peter Denifl, Carl-Eric Wilen. Porous Versus Novel Compact Ziegler–Natta Catalyst Particles and Their Fragmentation During the Early Stages of Bulk Propylene Polymerization J.Appl.Polym.Sci., 110 (4), 2008, 2021-2029 The effect of the porosity of Ziegler–Natta catalyst particles on early fragmentation, nascent polymer morphology, and activity were studied. The bulk polymerization of propylene was carried out with three different heterogeneous Ziegler–Natta catalysts under industrial conditions at low temperatures, that is, with a novel selfsupported catalyst (A), a SiO2-supported catalyst (B), and a MgCl2-supported catalyst (C), with triethyl aluminum as a cocatalyst and dicyclopentyl dimethoxy silane as an external donor. The compact catalyst A exhibited no measurable porosity and a very low surface area (<5 m2/g) by Brunauer–Emmet–Teller analysis, whereas catalysts B and C showed surface areas of 63 and 250 m2/g, respectively. The surface and cross-sectional morphologies of the resulting polymer particles at different stages of particle growth were analyzed by scanning electron microscopy and transmission electron microscopy. The compact catalyst A showed homogeneous and instantaneous fragmentation already in the very early stages of polymerization, which is typically observed for porous MgCl2-supported Ziegler–Natta catalysts. Moreover, the compact catalyst particles gave rise to almost perfectly spherical polymer particles with a smooth surface. In contrast, the silicasupported catalyst B gave rise to particles having a cauliflower morphology, and the second reference catalyst C produced fairly spherical polymer particles with a rough surface. All of the three catalysts exhibited similar activities of 450 g of polypropylene/g of catalyst after 30 min of polymerization, and most interestingly, the comparative kinetic data presented indicated that the reaction rates were not influenced by the porosity of the catalyst. printme	2008
Indicator Displacement Assays as Molecular Timers 2008, Andrey Buryak, Friederike Zaubitzer, Alexei Pozdnoukhov , Kay Severin . Indicator Displacement Assays as Molecular Timers J. Am. Chem. Soc., 130 (34), 2008, 11260-11261 Indicator displacement assays (IDAs) have emerged as powerful analytical tools. These assays are based on dyes or fluorescent ligands, which compete with analytes for the binding to synthetic receptors. Recent applications include the determination of catecholamines in urine samples, the threshold detection of malate in Pinot noir grapes, the sensing of nitric oxide, and the monitoring of glucose oxidase activity in blood serum. printme	2008
Thermorheological Properties of LLDPE/LDPE Blends: Effects of Production Technology of LLDPE 2008, Omar Delgadillo-Velazquez, S.G. Hatzikiriakos, M. Sentmanat. Thermorheological Properties of LLDPE/LDPE Blends: Effects of Production Technology of LLDPE Journal of Polymer Science Part B: Polymer Physics, 46 (16), 2008, 1669-1683 The thermorheological behavior of a number of LLDPE/LDPE blends was studied with emphasis on the effects of the production technology of the linear lowdensity polyethylene (LLDPE) and the effects of long chain branching (LCB). Two Ziegler-Natta LLDPEs (LL3001.32 and Dowlex2045G) and two metallocene LLDPEs (AffinityPL1840 and Exact 3128) were blended with a single low-density polyethylene (LDPE), with all LLDPEs having distinctly different molecular weight. The weight fractions of the LDPEs used in the blends were 1, 5, 10, 20, 50, and 75%. DSC analysis has shown that the blends with metallocence LLDPEs are miscible in the crystal state, whereas for the Ziegler-Natta, apart from the two distinct peaks of the individual components, a third peak appears which indicates the existence of a third phase that is created from the cocrystallization of components from the two blended polymers. The linear viscoelastic characterization was performed and mastercurves at 150 °C were constructed for all blends to check miscibility using the time temperature superposition principle. In addition, Van Gurp Palmen and zero-shear viscosity versus composition were constructed to check the thermorheological behavior of all blends. In general, good agreement is found among these various methods. It was concluded that metallocene LLDPEs are more compatible with LDPE at all LDPE compositions when compared with their Ziegler-Natta counterparts. Finally, the extensional properties of all blends were studied to examine the effects of different levels of LCB on their extensional rheological properties. It was concluded that extensional rheology is a sensitive tool capable of detecting subtle changes in the polyethylene macrostructure, that is, low levels of LCB. printme	2008
Capillary Extrusion Studies of LLDPE/LDPE Blends: Effects of Manufacturing Technology of LLDPE and Long Chain Branching 2008, Omar Delgadillo-Velazquez, S.G. Hatzikiriakos. Capillary Extrusion Studies of LLDPE/LDPE Blends: Effects of Manufacturing Technology of LLDPE and Long Chain Branching International Polymer Processing (4), 2008, 385-394 The processing behavior of a number of LLDPE/LDPE blends with emphasis on the effects of manufacturing technology of LLDPE and long chain branching is presented. A single low-density polyethylene was blended with two Ziegler-Natta linear-low-density polyethylenes LLDPE and apos;s and two metallocene-LLDPE and apos;s having distinctly different molecular structures. The weight fractions of the LDPEs used in the blends were 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, 50 wt.% and 75 wt.%. Capillary extrusion reveals that the onset of sharkskin and gross melt fracture are slightly influenced with the addition of LDPE into LLDPE. However, the amplitude of the oscillations in the stick-slip flow regime was found to scale well with the weight fraction of LDPE even at amounts as low as 1 wt.%. Furthermore, it was observed that the onset of this flow regime was shifted to higher shear rates with increase of LDPE content. Shear rheology was found to be insensitive to detect small levels of LDPE. On the other hand, extensional rheology was found to be capable of detecting levels of LDPE as low as 1 wt.% at high Hencky strain rates (typically greater than 5 s.sup.-1) although only for certain blends. printme	2008
Shear and elongational flow behavior of solutions. Part II: effect of gel content 2008, Saeid Kheirandish, Ilshat Gubaydullin, N Willenbacher. Shear and elongational flow behavior of solutions. Part II: effect of gel content Rheologica Acta DOI 10.1007/s00397-008-0324-x, 2008 We have investigated the effect of crosslink density on shear and elongational flow properties of alkali-swellable acrylic thickener solutions using a mixing series of the two commercial thickeners Sterocoll FD and Sterocoll D as model system. Linear viscoelastic moduli show a smooth transition from weakly elastic to gel-like behavior. Steady shear data are very well described by a single mode Giesekus model at all mixing ratios. Extensional flow behavior has been characterized using the CaBER technique. Corresponding decay of filament diameter is also well fitted by the Giesekus model, except for the highest crosslink densities, when filament deformation is highly non-uniform, but the non-linearity parameter a, which is independent of the mixing ratio, is two orders of magnitude higher in shear compared to elongational flow. Shear relaxation times increase by orders of magnitude, but the characteristic elongational relaxation time decreases weakly, as gel content increases. Accordingly, variation of gel content is a valuable tool to adjust the low shear viscosity in a wide range while keeping extensional flow resistance essentially constant. printme	2008
Influence of shear and extensional properties on the development of melt flow instabilities during extrusion based processes 2008, Susana Filipe, Saeid Kheirandish, Bernhard Knogler. Influence of shear and extensional properties on the development of melt flow instabilities during extrusion based processes Iberian Rheology Conference, Madrid, Spain, September 11-12 Also in Rheology in Product Design and Engineeringâ, Guerrero A. et. al editors. 2008. ISBN 978-84-608-0779-7, pp. 179-183., 2008 Considerable research has been focused on the influence of molecular weight, molecular weight distribution and topology on the onset and magnitude of melt flow instabilities developed during extrusion[1-4]. Within the conducted research the focus has been mainly on the investigation of HDPE, LDPE and LLDPE[1-4]. The sensitivity of small amplitude oscillatory shear (SAOS) towards changes in molecular character was used to understand the relevant rheological parameters correlating with the type and magnitude of the instabilities developed during extrusion[1,3]. In a recent work, an experimental correlation was found between the non-linear behaviour under Large Amplitude Oscillatory Shear (LAOS) flow and the development of melt flow instabilities during capillary extrusion. The importance of both extensional flows and non-linear viscoelasticity on industrial processes justifies a more in-depth analysis of the rheological behaviour under these conditions. Within this work, it is intended to establish a correlation between the non-linear viscoelastic behaviour (under both elongational and shear flow) and the development of melt flow instabilities for blends of linear polypropylenes with a high melt strength polypropylene. printme	2008