Improving the flame retardancy and water resistance of polylactic acid by introducing polyborosiloxane microencapsulated ammonium polyphosphate

Ammonium polyphosphate (APP) was respectively microencapsulated with polysiloxane (Si) and polyborosiloxane (BSi), and then were introduced into polylactic acid (PLA) to synchronously improve the flame retardancy, water resistance and mechanical properties of PLA composite. Fourier transform infrared (FTIR)/energy dispersive spectrometer (EDS) analysis and scanning electron microscopy (SEM) observation confirmed that the APP was successfully microencapsulated with Si and BSi, respectively. The flammability evaluation for the PLA/5%BSi-APP samples by limit oxygen index (LOI), UL-94 vertical burning test and cone calorimeter test (CONE) revealed the LOI value achieved to 26.7%, UL-94 grade reached up to V-0, and the peak heat release rate (HRR) was decreased significantly. The microencapsulation of APP also improved the compatibility of APP with PLA, resulting in better mechanical properties than control APP contained composites under the same loading. The water resistance of PLA composite was also significantly improved by the introduction of microencapsulated APP.