Change search
ReferencesLink to record
Permanent link

Direct link
Heat release and structural collapse of flexible polyurethane foam
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.
2010 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 6, 1115-1122 p.Article in journal (Refereed) Published
Abstract [en]

Flexible polyurethane foam used in upholstered furniture remains one of the major fire hazards to date. The heat release rate of burning items made of foam depends strongly on the foam’s physical behavior, notably its collapse to a burning liquid that can result in a pool fire. In this contribution, the cone calorimeter was used to study the physical processes and to determine their influence on foam combustion over a range of external heat fluxes. The initial stage of foam collapse can be described as the propagation of a liquid pyrolysis layer through the foam sample. The rate of propagation of the liquid layer was found to depend strongly on the convective heat transfer from the flame, which simultaneously defined and depended on the sample shape. The effective heat of combustion during foam collapse and pool fire was matched to the heat release potential of the components of the foam formulation to deduce which are consumed. The proposed analysis can serve to clarify the mechanism of flame retardant action, as demonstrated for a commercial brominated-phosphorous compound.

Place, publisher, year, edition, pages
2010. Vol. 95, no 6, 1115-1122 p.
Keyword [en]
Cone calorimeter; Convective heat transfer; Effective heat of combustion; External heat flux; Flexible foams; Flexible Polyurethanes; Foam collapse; Foam formulation; Heat release; Heat release rates; Initial stages; Liquid layer; Physical behaviors; Physical process; Pool fires; Rate of propagation; Sample shape; Structural collapse; Upholstered furniture, Combustion; Flame retardants; Liquids; Phosphorus; Rigid foamed plastics; Thermochemistry, Fire hazards
National Category
Polymer Chemistry
URN: urn:nbn:se:kth:diva-14211DOI: 10.1016/j.polymdegradstab.2010.02.019ISI: 000278750800027ScopusID: 2-s2.0-77953232908OAI: diva2:331775
Formas, 243-2004-1748
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2011-11-06Bibliographically 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.
Trita-CHE-Report, ISSN 1654-1081 ; 2009:5
Melt, flow, dripping, collapse, combustion, pool fire, feed‐back, gasification, heat release, flammability, nanocomposites, molar mass, intumescence, polyurethane
National Category
Polymer Chemistry
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)
QC 20100726Available from: 2009-03-11 Created: 2009-03-11 Last updated: 2010-07-26Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Krämer, RolandGedde, Ulf W.
By organisation
Polymer TechnologyFibre and Polymer Technology
In the same journal
Polymer degradation and stability
Polymer Chemistry

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 326 hits
ReferencesLink to record
Permanent link

Direct link