I want to use pa6 for additive manufacturing. My goal is to use the components above 200 degrees celsius. My part has be dimensionally stable at 200 degrees celsius. I am confused between Tg and Tm. I know that i can use pa6 above Glass transition temperature because it semi crystalline polymer but i want to know till what temperature i can use it.
Below the glass transition temperature (Tg) an amorphous polymer is hard and relatively brittle, i.e. it is considered to be in its "glassy" state. Above the Tg the amorphous polymer assumes a viscous (or rubbery) state. In other words, above the Tg the polymer softens abruptly.
The melting temperature (Tm) is a peculiar characteristic of semi-crystalline polymers. Below Tm the crystalline domains in the polymer remain substantially unchanged (even at T>Tg), thus allowing the polymer to retain its shape even in the rubbery state. Above Tm the crystalline domains are fused and the polymer can finally flow as a viscoelastic fluid.
Some polymers show some degree of crystallinity (this is the case of poly[imino (1-oxohexane-1,6-diyl)], also known as polyamide 6 or Nylon 6). Semi-crystalline polymers exhibit both Tg and Tm. In the case of PA6: Tg = 40-60 ° C; Tm = 210-220 ° C, source: https://www.perkinelmer.com/CMSResources/Images/44-74863TCH_MPTGAndStructureOfCommonPolymers.pdf .
To use PA6 or PA6-GF30 in additive manufacturing, it is necessary to exceed Tm (for example, Prusa recommends a nozzle temperature of 250 ° C for a generic nylon filament: https://help.prusa3d.com/en/article/nylon_167188). The optimized temperature must be defined with a series of tests, taking into account the specific material/composite you want to use and the machine you want to use it on.
The final product should be stable up to 300 °C. This is generally the temperature above which nylon begins to decompose. Then again, this temperature should be defined for your specific material (a Thermogravimetric analysis, TGA, is sufficient) as it can vary depending on several factors. ( Schindler, A., Doedt, M., Gezgin, Ş. et al. Identification of polymers by means of DSC, TG, STA and computer-assisted database search. J Therm Anal Calorim 129, 833–842 (2017). https://doi.org/10.1007/s10973-017-6208-5 ).
Finally, nylon generally starts to flow above 220 °C, so an operating temperature of 200 °C for the final product may be too high. It depends on the stress that the product has to withstand.
Best regards
Dear Mr Niccolò Braidi
Thank very much for such a good explaination. Explaination is very good referance to clear my all questions.
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