The flame retardant effect is preliminarily based on the physical formation of a highly expanded, thermally stable residue and can thus be incorporated into different polymeric systems. Compared to other flame retardant additives, expandable graphites are low cost and provide a good flame retardancy effect characterized by low smoke generation and an anti-dripping effect. Įxpandable graphites (EG) are successfully used as flame retardant additives predominantly in polyurethane (PU) foams, gaskets and flame retardant coatings. Since intrinsically flame retardant polymers available today mostly exceed the cost of conventional polymers many times over, modification of conventional grades with flame-retardant additives is the most widely used alternative in order to fulfill stringent flame retardancy standards. Today, the majority of polymers used in technical applications naturally exhibit poor flame retardancy properties and thus require either molecular or additive modification to lower the probability of a fire hazard. Accordingly, humid-conditioned samples containing between 2.5 (PA6 + 25 wt.% EG) and 4.2 wt.% (PA6) water were found to reduce the total heat evolved (THE) on average by 16% and the total smoke production (TSP) on average by 22%. Correlation analyses were conducted to identify major influences given by the sample condition for most important key figures measured in cone calorimeter tests. UL-94 fire tests show a V0 classification at filling degrees greater than 20 wt.% (humid) and 25 wt.% (dry), although the associated LOI values of 39% and 38% demonstrate good flammability inhibition. Cone Calorimeter tests showed a minimum filling degree of 15 wt.% (8.6 vol.%) EG was required to achieve a significant fire inhibiting effect in PA6 independent of the sample condition. Fire tests were conducted using dry and humid conditioned samples.

Additionally, electric and thermal conductivity as well as rheological properties were characterized to provide a general property overview. The fire behavior was characterized by a cone calorimeter using external heat fluxes of 35, 50 and 65 kW/m 2, limiting the oxygen index (LOI) and UL-94 burning tests. A new expandable graphite (EG) type was studied as a flame retardant additive in Polyamide 6 (PA6).

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