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On the intumescence of ethylene-acrylate copolymers blended with chalk and silicone
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2007 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 92, 1899-1910 p.Article in journal (Refereed) Published
Abstract [en]

The combustion and melt dripping of poly(ethylene-co-butyl acrylate) (EBA), EBA blended with polypropylene (EBA-PP) and poly(ethylene-co-methacrylic acid) (EMAA), each blended with calcium carbonate and polydimethylsiloxane, were studied. In situ measurement of the temperature gradient in the cone calorimeter were combined with infrared spectroscopy measurements on specimens withdrawn and quenched at different times of the experiment. The reactions that govern the degradation at the high heating rates met in the combustion could be determined and the gap to analytical techniques such as thermogravimetry bridged. The interplay of mechanical char integrity and heat feedback by the flame determined how much time the specimen dwells in temperature range of 300-420 °C where char expansion due to calcium salt formation is effective and thereby affects the heat release rate strongly. Vertical cone calorimeter and vertical flame testing were used to assess melt dripping and char stability under flaming combustion. Plate-plate rheological measurements proofed to be of limited use to compare the effect of different degradation atmospheres on the melt viscosity. The EMAA formulation had the most effective intumescent process with a low heat release rate and good char stability even in vertical configuration. Electron-beam irradiated EMAA specimens with different levels of cross-links were tested in the cone calorimeter in order to understand the role of cross-links for the intumescent process.

Place, publisher, year, edition, pages
2007. Vol. 92, 1899-1910 p.
Keyword [en]
Acrylics; Flame retardants; Heating rate; Infrared spectroscopy; Polydimethylsiloxane; Polymer blends; Thermal gradients, Calcium carbonate; Chalk; Intumescence, Copolymers
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-14212DOI: 10.1016/j.polymdegradstab.2007.06.014ISI: 000250950300018Scopus ID: 2-s2.0-34948885154OAI: oai:DiVA.org:kth-14212DiVA: diva2:331776
Note
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Melt flow and surface stability effects on polymer flammability: A study on polystyrene, flexible polyurethane foam and polyolefin composites
Open this publication in new window or tab >>Melt flow and surface stability effects on polymer flammability: A study on polystyrene, flexible polyurethane foam and polyolefin composites
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Our ability to accurately determine the flammability properties of polymers is hampered bythe erratic effects of deformation and liquid flow that occur during polymer combustion.This study aims to improve the understanding of such effects at several levels:

The often obvious impact of melt flow on standardized flammability test methods forelectrical appliances is described to identify the need and to motivate others to worktowards an improved material characterization.

The production of a burning degraded melt results from both, melting anddecomposition of thermoplastic polymers. The degradation of the polymer chains yieldsboth combustible volatiles that feed the flame and smaller molecules with a low viscositythat might spread to a burning pool. The molar mass is the property of the material that linksboth processes. Changes in molar mass at the surface of specimens exposed to fire‐like heatfluxes were analyzed, using polystyrene as a model thermoplastic material. Analyticalexperiments were combined with bench‐scale gasification and gasification/melt flowexperiments, in order to determine the extent of viscosity reduction by melting and bypolymer decomposition.

A strong volume contraction to a low viscous liquid is characteristic for the combustionof flexible polyurethane foam, a low density cellular material used for cushions in furnitureand mattresses. Foam decomposition is initiated at low temperature (< 300 °C), yieldingignitable gases and leading to a fast flame spread that results in the formation of a burningliquid pool. The foam morphology changes rapidly during combustion and the impact ofthese changes on the heat release rate was analyzed. The distribution of flame heat transferled to strong variations in the burning rate, which shaped the specimen surface. The shapeof the surface affected in turn the distribution of flame heat flux, leading to an interlockingprocess. A custom‐made vertical test arrangement gave the ability to study the effect of heatfeedback from the burning liquid. Foam composites with carbon nanofibers and organicallymodified clay were prepared with the aim to eliminate liquefaction. Incorporation of anetwork of carbon nanofibers in the foam struts is demonstrated to prevent foamliquefaction and collapse.

An approach to prevent melt‐dripping is the use of high filling levels of inorganicparticles in polyolefin cable materials and to promote reactions between the filler and thepolymer. The transition from a polymer melt to an immobile inorganic residue was studiedfor blends of acrylic copolymers of ethylene with chalk and silicone. The mechanical stabilityof the inorganic surface layer that formed during combustion was decisive for the materialsflammability properties. In‐situ thermocouple measurements and ex‐situ analysis of partiallyburned specimen surfaces were used to explain the coupling between the degradationmechanism of the polymer and the heat shield effect of the inorganic residue layer.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 60 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:5
Keyword
Melt, flow, dripping, collapse, combustion, pool fire, feed‐back, gasification, heat release, flammability, nanocomposites, molar mass, intumescence, polyurethane
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-10079 (URN)978-91-7415-239-5 (ISBN)
Public defence
2009-03-20, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100726Available from: 2009-03-11 Created: 2009-03-11 Last updated: 2010-07-26Bibliographically approved

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