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: 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

Title	Year
The role of grafting and network formation on the extractability of antioxidants in crosslinked polyethylene 2005, Ann-Christin Augustsson, Thomas Hjertberg, Ann-Charlott Ivarsson, Magnus Palmlof. The role of grafting and network formation on the extractability of antioxidants in crosslinked polyethylene Polymerdagarna, G6teborg, Sweden, August 17-19, , 2005 are several methods for production of crosslinked polyethylene (PEX) on an industrial scale and important applications are pipes for hot water and cable insulation. To enhance the resistance to thermal oxidation and thereby increase the lifetime of the product, antioxidants are added. For water pipe applications it is important that the water does not wash out the antioxidants which would lead to decreased stabilising effect. It has been shown that the extractability of substances in PEX is lower than for PE, but it is not clear why. One theory is that the antioxidant molecule is grafted via a radical mechanism onto the polymer backbone in the crosslin king step; another suggestion is that the network would be tight enough to enclose the molecule and hold back migration. The extractability can also vary between different types and grades of PEX. For the future development of new materials it is important to reach a better understanding of the interaction between the antioxidant and the polymer. By investigating silane crosslinkable materials, it has been possible to separate the effect of grafting from the effect of the network formation. Results have been used to some extent facilitate the interpretation of data obtained from free radical crosslinking processes. The work has led to the conclusion that grafting of antioxidants on PE is indeed possible if these are subjected to free radicals. Grafting is therefore one possible explanation to why antioxidants can only partly be extracted from crosslinked PE by organic solvents. Hence grafting creates a polymer bound stabiliser. At grafting, some antioxidant molecules are likely to loose their antioxidant function whereas others can maintain it. Possible mechanisms are proposed from literature. However, on extraction of crosslinked PE in organic solvents, the network formation as such does not seem capable to reduce the extractability of antioxidants. printme	2005
Unexpected reactions/interactions of phosphites within polyolefin stabilisation 2005, Svein H. Jamtvedt, Harry Øysæd. Unexpected reactions/interactions of phosphites within polyolefin stabilisation Addcon World 2005, Hamburg 21-22.09., 2005 Polyolefins are prone to degradation during compounding, converting to final products and end use. The degradation proceeds in a free radical mechanism and will finally destroy the polymer properties. Phenolic antioxidants and phosphites are important stabilisers to protect polyolefins during processing and end use. Phenolic antioxidants give good contribution to process -stability and especially long term heat stability (LTHS) of polyolefins. The main drawback is contribution to discolouration, mainly yellowing. Phosphites are known to give good process stability together with phenolic antioxidants, but very limited contribution to LTHS. High performance phosphites are contributing to a total good colour of the final product. A combination of phenolic antioxidant(s) and phosphite(s) give synergistic effect. The reason for this is that they take care of different degradation products. A surprising reaction with high performance phosphites/phosphonite has been experienced in LPPE based on Cr-catalyst on silica carrier. During storage of such PE at ambient temperature the residual catalyst system is capable of hydrolysing the phosphites. The end result is that original phosphite is not traceable after few months storage, while the starting alkyl phenol, e.g. 2,4-di-tert. butyl phenol, will appear. Process stability test of a few months old granules has shown reduced stability with gels and stripe-formation as the result. A positive surprise with phosphites has been observed in PP. It is possible to boost LTHS significantly with selected phosphites in combination with phenolic antioxidant(s) and thiosynergists (e.g. DSTDP). Normally the role of phosphites has been seen to protect PP during processing and thereby also reduce the reaction the phenolic antioxidant during processing. This will give only marginally (if any) increase in LTHS printme	2005
The Continuing Evolution of Semiconductive Materials for Power Cable Applications 2005, Karl-Michael Jäger, Lena Lindbom. The Continuing Evolution of Semiconductive Materials for Power Cable Applications IEEE Electrical Insulation Magazine, 21 (1), 2005, pp 20-34 The reliability of XLPE power cables has improved continuously since this technology was introduced in the early 1960s, to complement and then replace paper-insulated cables. The most important development steps have been the introduction of extruded conductive screens (screens are known as shields in North Americas), triple extrusion, N2-gas curing (instead of steam curing), higher requirements on cleanliness of the XLPE compounds, and the use of high quality semiconductive materials. All of the improvements have, together, enabled safe design and production of reliable cables. However, it is this last contributions, from semiconductive materials, that we focus on in this article. printme	2005
Introduction of long-chain branches in linear polyethylene by light cross-linking with 1,3-benzenedisulfonyl azide 2005, Jens Kjær Jørgensen, Aage Stori, Keith Redford, Espen Ommundsen. Introduction of long-chain branches in linear polyethylene by light cross-linking with 1,3-benzenedisulfonyl azide Polymer, 46, 2005, 12256-12266 Metallocene synthesised HDPE with MwZ82,000 and MnZ40,000 was modified with small amounts of 1,3-benzenedisulfonyl azide by reactive extrusion at 200 °C with the purpose to form long-chain branches. At the processing temperature the two azide groups decompose to nitrenes that work as cross-linkers for PE. Cross-linking occurs primarily by insertion of singlet nitrenes into CH bonds. Size exclusion chromatography revealed that the modification resulted in the formation of a long-chain branched (LCB) high molecular weight fraction. The LCB was detectable with SEC for concentrations above 100 ppm corresponding to approximately 0.03-0.04 branch points pr 104 carbon. No signs of the formation of low molecular species due to chain scission were observed. Dynamical mechanical analysis and shear creep test showed sign of long chain branching at concentrations down to the same limit as SEC (100 ppm). These signs were thermorheological complexity, increased zero shear viscosity, increased shear thinning and increased recovery compliance. The cross-linking efficiency of 1,3-BDSA were estimated to 40-60% from comparison of SEC data with random cross-linking theory and traditional SEC-LCB analyses. printme	2005
Synthesis, characterisation and decomposition of 1,3-benzene disulfonyl azide; a cross-linking agent for polyolefins 2005, Jens Kjær Jørgensen, Espen Ommundsen, Aage Stori, Keith Redford. Synthesis, characterisation and decomposition of 1,3-benzene disulfonyl azide; a cross-linking agent for polyolefins Polymer, 46, 2005, 12073-12080 We have studied the thermal decomposition of 1,3-benzenedisulfonyl azide (1,3-BDSA), and verified that sulfonyl nitrenes formed are able to cross-link polyolefins, including PP. The decomposition was studied with DSC, TGA, and the GC-MS analysis of gaseous products. Both the decomposition of pure 1,3-BDSA and 1,3-BDSA dissolved in a polyolefin were studied. Decomposition occurs by loss of nitrogen giving sulfonyl nitrenes. In the polyolefin nitrenes cross-links the carbon hains by C¿H insertion. Cross-linking of PP was verified with SEC. SEC showed no signs of decomposition of PP. Decomposition in the polyolefin was a first order reaction with a half-life of 25.7 s at 200 °C. Hence, 1,3-BDSA is suited for processing with polyolefins. Decomposition of pure 1,3-BDSA is more complicated with unwanted products such as SO2 and benzene being formed, thereby emphasising the need for good blending when used in polyolefins. printme	2005
In the Overtaking Lane - Transparent PP bottles 2005, Markus Gahleitner, Max Wachholder. In the Overtaking Lane - Transparent PP bottles Kunststoffe plast europe, 95, 2005, 177-179 Injection stretch blow moulding, short ISBM, is THE way to produce glass-clear bottles from PP for a wide variety of applications - from dairy products through fruit juices to household detergents. Borealis has made some significant developments in this sector. These are highlighted together with the latest trends in extrusion blow moulding. printme	2005
Morphology and properties of reactively modified heterophasic polypropylene 2005, Tung Pham, Markus Gahleitner. Morphology and properties of reactively modified heterophasic polypropylene 21st Annual Meeting of the Polymer Processing Society, Leipzig, Germany, 19.-23.06., 2005 Polypropylene is one of the fastest growing commodity resins in the polymer world market. Compared to other thermoplastics, polypropylene shows very well balanced property combination such as low density, high melting point, high stiffness and low cost. Heterophasic polypropylene (impact polypropylene) is widely used in applications where high impact resistance is required such as automobile parts, household articles etc. In the past, the most common method for generating such multiphase polypropylene systems is melt mixing of homo-polypropylene and an external rubber component. Nowadays, using modern polymerisation technologies, impact polypropylene with variable property combinations could be produced via multistage reactor arrangements. The adjustment of the final properties of heterophasic polypropylene (flowability, stiffness, toughness, etc.) could be controlled by the polymer composition, polymerisation parameters as well as by the post reactor modification step. In this paper, the effects of reactive post modification on the formation of ethylene-propylene copolymer grafted to polypropylene - which is believed to be the main reason for the strengthened interface between the PP matrix and EPR particles -, the phase morphology and final material properties have been investigated using a model system and demonstrated in a specific example on high flow materials for thin wall injection moulding. Depending on practical application requirements, well defined material performance such as toughness, flowability etc. could be adjusted.. printme	2005
Prediction Formulas for Melt Indexes of Blends of Linear PE's. 2005, Arild Follestad. Prediction Formulas for Melt Indexes of Blends of Linear PE's. PPS-21, Leipzig, June 22,, 2005 Polyethylene is usually used in the form of homogeneous blends consisting of components of different molecular weights. These blends to some extent have been supplied as such from the polymer producer, but additional blending is often done by the converter. Numerous melt index (/viscosity) formulas from the literature for prediction of melt indexes of a blend from that of its components have been compared. Some are to a large extent empirical, based on a limited set of experimental data, others are mainly based on theory. The quality of these formulas has been investigated by using a collection of data sets from various sources, together covering a very wide experimental range. Some deviations are very large, few formulas manage the whole range reasonably well. An improved formula covering all homogeneous linear polyethylene blends is suggested. This form is probably applicable also to other blends of linear polymers. Limitations /pitfalls to such a formula, mainly to the homogeneous melt criterion, are further discussed. printme	2005
Flexible Polypropylene Foam Solutions 2005, Manfred Stadlbauer, Rick Folland, Paul De Mink. Flexible Polypropylene Foam Solutions RAPRA Blowing Agents and Foaming Processes 2005, Stuttgart, Germany, 10-11 May,, 2005 A novel resin for flexible polypropylene foam is presented. The new grade enables stiffness-reduction by 50% over state-of-the-art polypropylene foams (at same density). Furthermore, it expands the processing window through high melt strength and slower solidification of the super-cooled melt. The present paper outlines mechanical properties, model calculations and experimental foaming studies with the new HMS-PP for soft and flexible polypropylene foam. printme	2005
Surface Stability of Polypropylene Compounds and Paint Adhesion 2005, Eberhard Ernst, Jens Reussner, Peter Pölt, Elisabeth Ingolic. Surface Stability of Polypropylene Compounds and Paint Adhesion Journal of Applied .Polymer .Science, 97, 2005, 797-805 Thermoplastic olefins based on polypropylene compounds are being increasingly used for the production of painted automotive parts. The poor adhesion properties of these compounds are improved with flaming, which results in good adhesion for waterborne paints. The surface stability and adhesion properties of two commercial injection-molded compounds and their base polymer blends (polypropylene/ethylenepropylene rubber) were investigated after they were flamed with various parameters under typical vapor jet conditions. The compounds and the corresponding base blends showed mainly the same behavior. Thus, filler particles and additives seemed to have only a minor influence on the adhesion properties of these compounds. For the characterization of the surface itself and the near-surface region, scanning and transmission electron microscopy, XPS, and microthermal analysis were used. The utmost surface layer for all specimens consisted of a skin of pure polypropylene. The oxygen concentrations at the surface after flaming were rather similar for both compounds. Differences could be found in the surface roughness, the oxygen diffusion from the interior to the surface, and, probably most importantly, the viscosity and elasticity of the impact modifier. printme	2005