Normally after addition of graphene into polymers, TTI will increase indicating an improvement in flammability resistance.
If the TTI decrease after incorporation of graphene, what is the possible reason?
How pure is the graphene? Is it possible that some oxygen still remain on the surfaces of the graphene sheets?
We used two types; Graphene oxide (GO) and Graphene Nanoplatelets (GNP).
TTI for GO filled PBT nanocomposites is longer than GNP Filled PBT nanocomposites.
However, unexpectedly TTI for pure PBT is longer.
I am finding reasons for that.
Could it be because possibly PBT is irradiated? and at high temps the branching is induced. but Graphene on the other hand, prevents the branching and crosslinking, hence TTI is less.
Azman Hassan The reduction in TTI arises from the black color of carbonacaeous additive (in this case graphene) which causes the increased radiant heat absorption within the top layer of the material during cone callorimeter test. We stated this assumption in our research studies related with:
expandable graphite: 10.1016/j.tca.2016.12.001
fullerene: 10.1177/0095244318796616
by citing these references:
- 10.14314/polimery.2013.361
- 10.1016/j.polymdegradstab.2013.04.009
It would be useful to compare thermal conductivity of these three materials. May be this will help to understand the difference in their TTI as thermal conductivity, in addition to other factors, affects heat release rate and, therefore, flame spread rate.
Dear Azman Hassan
In my opinion, the weak interfacial bonding and poor homogeneous dispersion of graphene in the polymer matrix are behind the TTI reduction.
Best regards
In my opinion, the graphene acts like catalytic booster to activate reactions, plus the other properties.
We get same results for PE flame retardant loaded like phosphorus but yet the test was weak when load of carbonaceous component was added (CNT there)
Dear Azman Hassan
Apart from tortuous properties which result from homogeneous dispersion of graphene in composites, Graphene has inherent barrier characteristics which play an important role in flame retardancy of polymer composites by increasing the Limiting Oxygen Index of the composites in which it is used.
Thermal conductivity is a key role in a burning component, nanocarbon atoms are the best there, then it could be the epxlanation of that behaviour.
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