At around 140 °C endothermic peaks are found in the heating cycles for a glass fibre reinforced polyamide 6 sample. No use of lubricants is mentioned by the supplier. Could this be a result of moisture in the sample or rather of another compound present?
I would say that the mentioned glass fibre reinforced polyamide-6 composite may contain a small amount of some compatibilizing agent, which apparently melts by around 140 °C. Prior humidity conditioning of the sample seems advisable.
Dear Maarten,
Traditionally for the reinforcing of polyamides with previously adequately surface treated glass fibers, for better melt-compounding and processing, are added some specific additives (like lubricants, thermal stabilizers, nucleating agents, compatibilizers, etc.). Some common lubricants/release agents like ethylene bis stearamide (EBS) with a melting point above 143°C, metal stearates, montan esters, and so on, are often used.
By looking at your DSC results, based on my practical experience with PA6, my choice is going to the utilization of magnesium stearate (melting point about 140°C) which is between the key-additives for the processing of polyamides. However, because the nature of additives and compatibilizers is very large, my assumption must be supported by some additional analyses (e.g., EDX, others).
Good luck in your research and best regards,
Marius
PS: For eventual help, some information about sterates:
https://www.brenntag.com/media/documents/bsi/product_data_sheets/life_science/bsi_stearates/brochure_stearates.pdf
https://www.hallstar.com/webfoo/wp-content/uploads/hallstar-metallic-stearates-for-rubber-compounds.pdf
Maarten.. Exclude the moisture from your explanation. The details given by Marius above is fair.... Regards
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