The limiting oxygen index (LOI) could be raised to 44% for the PLA composite with 29 wt% ATH and 1% HBP6. A UL-94 V-0 rating could be achieved by adding ATH and HBP6 to the PLA matrix. The HBP6 has a lower glass transition temperature (Tg), approximately −31 °C, and its incorporation as a plasticizer could increase the impact strength of a PLA blend or composite. The elongation at break could be increased from 5% for neat PLA to 83% for the PLA composite with an addition of 10% of HBP6 and 20% ATH. The enhancement of impact strength of the composite was not only attributed to the decrease in Tg, but also the dispersion of second-phase HBP6 domains formed by the phase separation.