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Investigation on the Flame Retardant Properties and Fracture Toughness of DOPO and Nano-SiO2 Modified Epoxy Novolac Resin and Evaluation of Its Combinational Effects

1
Department Polymer Engineering, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
2
DWI–Leibniz-Institute for Interaktive Materials Aachen, Forckenbeckstraße 50, 52056 Aachen, Germany
3
BASF Polyurethanes GmbH, Elastogranstraße 60, 49448 Lemfoerde, Germany
4
ITMC-Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany
*
Authors to whom correspondence should be addressed.
Materials 2019, 12(9), 1528; https://doi.org/10.3390/ma12091528
Received: 11 April 2019 / Revised: 29 April 2019 / Accepted: 8 May 2019 / Published: 10 May 2019
(This article belongs to the Special Issue Advanced Flame Retardant Materials)
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Abstract

In this study, the flame-retardant, thermal and mechanical properties of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and nano-SiO2 modified epoxy novolac resin is evaluated, and the combinational effects of both additives are verified. As a hardener, an isophorone diamine (IPDA) and polyetheramine blend is stoichiometrically added to obtain a low viscous epoxy resin system, suitable for resin injection and infusion techniques. The glass transition temperature (Tg) and the silica dispersion quality is affected by the DOPO modification and the nano silica particles. The flame-retardant (FR) and mechanical properties of the additives are investigated separately. The fracture toughness could be increased with the incorporation of both FR additives; however, the effect is deteriorated for higher DOPO amount which is referred to silica particle agglomeration and consequently reduced shear yielding mechanism. Flame-retardant properties, especially the peak heat release rate (pHRR) and the total heat release (THR) could be decreased from 1373.0 kW/m2 of neat novolac to 646.6 kW/m2 measured by resins with varying phosphorous and silica content. Thermogravimetric analysis (TGA) measurements show the formation of a high temperature stable char layer above 800 °C which is attributed to both additives. Scanning electron microscopy (SEM) images are taken to get deeper information of the flame-retardant mechanism, showing a dense and stable char layer for a certain DOPO silica mixture which restrains the combustible gases from the burning zone in the cone calorimeter test and influences the fire behavior of the epoxy resin. View Full-Text
Keywords: epoxy novolac resin; DOPO; nano-SiO2; flame retardancy; fracture toughness epoxy novolac resin; DOPO; nano-SiO2; flame retardancy; fracture toughness
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Häublein, M.; Peter, K.; Bakis, G.; Mäkimieni, R.; Altstädt, V.; Möller, M. Investigation on the Flame Retardant Properties and Fracture Toughness of DOPO and Nano-SiO2 Modified Epoxy Novolac Resin and Evaluation of Its Combinational Effects. Materials 2019, 12, 1528.

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