Dear Meisam Shabanian, usually when to deal fire retardancy, phosphazene monomers and polymers are the best choice. For the case you are working on, please check the following documents. My Regards

https://doi.org/10.1177/0731684407084121

https://doi.org/10.1021/ma047514t

Try with nano ingredients: Cellulose nanofibers (CNFs), Zirconia, Titania TiO2, and others: glass fiber, Boron nitride, etc.

Dear Meisam,

Unfortunately, we do not have some more experimental details: the flame retardant properties are good enough (?), what is the melamine cyanurate loading, in fact, what are the mechanical properties that must be improved?

Following your question, I would like to share with you some points for discussion. Please consider that the melamine derivatives are traditional flame retardants for PA 6 and PA 6,6 compounds produced at industrial scale. In this context some, we must assume that the mechanical properties of PA- 6 flame retardant grades are remaining good .

Don’t forget that PA 6 is very sensitive to the absorption of water, maybe in your experiments this aspect was not enough considered, the high moisture content of PA 6 and FR additives can lead to the important degradation of PA 6 compounds. The morphology of compounds/dispersion of melamine cyanurate (MC) was good?

Regarding the mechanical properties, function of MC loading there are some expected few drawbacks (e.g., decrease of strain and impact strength), but also increases of Young’s modulus, flexural strength, etc., while keeping a good tensile strength. In this context, it could be helpful to look at the results reported in the literature or by industrial producers ( of FRs or FR PA 6 compounds).

Good luck in your R&D works and best regards,

Marius

Dear Meisam,

For eventual help:

Liu, Y., Wang, Q. The investigation on the flame retardancy mechanism of nitrogen flame retardant melamine cyanurate in polyamide 6. J Polym Res 16, 583–589 (2009). https://doi.org/10.1007/s10965-008-9263-6

Differences in the flame retardant mechanism of melamine cyanurate in polyamide 6 and polyamide 66, Polymer Degradation and Stability 78 (2002) 219–224, https://doi.org/10.1016/S0141-3910(02)00136-2

https://www.researchgate.net/publication/244357835_Differences_in_the_flame_retardant_mechanism_of_melamine_cyanurate_in_polyamide_6_and_polyamide_66

Preparation of flame retardant Polyamide 6/melamine cyanurate via in situ polymerisation and its characterization; July 2014, Material Research Innovations 18(S4):S4-843-S4-847

DOI: 10.1179/1432891714Z.000000000804

https://www.researchgate.net/publication/272253863_Preparation_of_flame_retardant_Polyamide_6melamine_cyanurate_via_in_situ_polymerisation_and_its_characterisation

Obtaining of Fire-retardant Polyamide 6 Grades without Halogens for Injection Moulding

Article Obtaining of Fire-retardant Polyamide 6 Grades without Halog...

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Good luck in finding the best alternative,

Marius