I recently measured the melt flow index (MFI) of the following materials at 210°C and 2.16 kg load:
- Polylactic acid (PLA): 28.38 g/10 min
- Thermoplastic polyurethane (TPU): 56.24 g/10 min
- PLA-TPU composite (50%-50% blend): 77.84 g/10 min
Theoretically, the MFI of the composite should fall between the individual values of PLA and TPU. However, the measured MFI of the composite is significantly higher than both PLA and TPU. This result is unexpected.
Could anyone suggest possible reasons for this behavior? Are there specific interactions or mechanisms between PLA and TPU in the composite that could explain this anomaly? Additionally, what experimental or processing factors could influence this outcome? Any insights or similar experiences would be greatly appreciated.
Dear Krishnanand, MFI is only meaningful for polyolrfins (PEs and PPs). Most probably this is due to the plasticization effect imparted by TPU to PLA. The solutions are either to crosslink or graft TPU into PLA matrix. My Regards
No thanks. The following free access RG paper may be interesting.
https://www.researchgate.net/publication/272105386_Effect_of_Carboxymethylcellulose_on_Plasticized_Polylactide
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