Effects of Combining Graphene Nanoplatelet and Phosphorous Flame Retardant as Additives on Mechanical Properties and Flame Retardancy of Epoxy Nanocomposite

Woranan Netkueakul; Beatrice Fischer; Christian Walder; Frank Nüesch; Marcel Rees; Milijana Jovic; Sabyasachi Gaan; Peter Jacob; Jing Wang

doi:10.3390/polym12102349

Effects of Combining Graphene Nanoplatelet and Phosphorous Flame Retardant as Additives on Mechanical Properties and Flame Retardancy of Epoxy Nanocomposite

Polymers (Basel). 2020 Oct 14;12(10):2349. doi: 10.3390/polym12102349.

Authors

Woranan Netkueakul^{1

2}, Beatrice Fischer³, Christian Walder³, Frank Nüesch³, Marcel Rees⁴, Milijana Jovic⁵, Sabyasachi Gaan⁵, Peter Jacob⁶, Jing Wang^{1

2}

Affiliations

¹ Institute of Environmental Engineering, ETH Zurich (Swiss Federal Institute of Technology Zurich), 8093 Zurich, Switzerland.
² Laboratory for Advanced Analytical Technologies, Empa-Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
³ Laboratory for Functional Polymers, Empa-Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
⁴ Laboratory for Mechanical Systems Engineering, Empa-Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
⁵ Additives and Chemistry Group, Advanced Fibers, Empa-Swiss Federal Laboratories for Materials Science and Technology, 9014 St. Gallen, Switzerland.
⁶ Electronics and Reliability Center, Empa-Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.

Abstract

The effects of combining 0.1-5 wt % graphene nanoplatelet (GNP) and 3-30 wt % phosphorous flame retardant, 9,10- dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as fillers in epoxy polymer on the mechanical, flame retardancy, and electrical properties of the epoxy nanocomposites was investigated. GNP was homogeneously dispersed into the epoxy matrix using a solvent-free three-roll milling process, while DOPO was incorporated into the epoxy resin by mechanical stirring at elevated temperature. The incorporation of DOPO reduced the crosslinking density of the epoxy resin. When using polyetheramine as a hardener, the structural rigidity effect of DOPO overshadowed the crosslinking effect and governed the flexural moduli of epoxy/DOPO resins. The flexural moduli of the nanocomposites were improved by adding GNP up to 5 wt % and DOPO up to 30 wt %, whereas the flexural strengths deteriorated when the GNP and DOPO loading were higher than 1 wt % and 10 wt %, respectively. Limited by the adverse effects on mechanical property, the loading combinations of GNP and DOPO within the range of 0-1 wt % and 0-10 wt %, respectively, in epoxy resin were further studied. Flame retardancy index (FRI), which depended on three parameters obtained from cone calorimetry, was considered to evaluate the flame retardancy of the epoxy composites. DOPO showed better performance than GNP as the flame retardant additive, while combining DOPO and GNP could further improve FRI to some extent. With the combination of 0.5 wt % GNP and 10 wt % DOPO, improvement in both mechanical properties and flame retardant efficiency of the nanocomposite was observed. Such a combination did not affect the electrical conductivity of the nanocomposites since the percolation threshold was at 1.6 wt % GNP. Our results enhance the understanding of the structure-property relationship of additive-filled epoxy resin composites and serve as a property constraining guidance for the composite manufacturing.

Keywords: flame retardancy; graphene nanoplatelets; mechanical properties; nanocomposites.

Grants and funding

310030_169207/Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung