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Modelling the vertical UL 94 test: Competition and collaboration between melt dripping, gasification and combustion



Florian Kempel, Bernhard Schartel, Julio M. Marti, Kathryn Butler, Riccardo Rossi, Sergio R. Idelsohn, Anja Hofmann


An experimental and numerical investigation of the impact of the additives bisphenol A bis(diphenyl phosphate) (BDP) and polytetrafluoroethylene (PTFE) on the fire behaviour of bisphenol A polycarbonate / acrylonitrile butadiene styrene (PC/ABS) in the vertical UL 94 scenario is presented. The main focus is on the different dripping behaviour. The series of materials consists of four PC/ABS blends, which cover different UL 94 classifications due to the competing effects of gasification, charring, flame inhibition and melt flow/dripping. For numerical investigation the Particle Finite Element Method (PFEM) is used. Its capability to model the complex fire behaviour of polymers in the UL 94 scenario is analysed. The materials properties and behaviour are characterized thoroughly. In particular the impact of the additives BDP and PTFE on the rheological characteristics is investigated. BDP is an efficient plasticizer; the addition of PTFE prevents samples from dripping because of the formation of a flow limit. Simulations with PFEM reproduce the dripping and burning behaviour in the vertical UL 94 test. The competition between gasification and dripping is simulated well. The thermal impact of the burner as well as of the flame is described by reasonable approximations taking into account flame inhibition, charring and effective heat of combustion. The study shows that PFEM is a promising numerical tool for the investigation of the fire behaviour of polymers, particularly when large deformations are involved. Not only the principle phenomena, but also the different UL 94 classifications and the time scale for extinction are predicted well.
Fire and Materials


melt dripping, rheology, UL 94, simulation, Particle Finite Element Method (PFEM), PC/ABS, BDP, PTFE


Kempel, F. , Schartel, B. , Marti, J. , Butler, K. , Rossi, R. , Idelsohn, S. and Hofmann, A. (2014), Modelling the vertical UL 94 test: Competition and collaboration between melt dripping, gasification and combustion, Fire and Materials, [online], (Accessed July 24, 2024)


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Created June 23, 2014, Updated October 12, 2021