Flame-retardant recycled bamboo chopstick fiber-reinforced poly(lactic acid) green composites via multifunctional additive system

• The hybrid reinforcements consist of recycled bamboo chopstick fiber and nano-clay.
• The hybrid reinforcements are surface modified and grafted onto PLA.
• Ammonium polyphosphate and expandable graphite were added as flame-retardants.
• The UL-94 flame test of the composites achieves a V-1 or V-0 grade.
• The tensile strength of PLA can be improved by 14.5%.

In this study, recycled bamboo chopstick fiber and nano-clay are utilized to reinforce poly(lactic acid) (PLA) biodegradable plastic. The chopstick fiber and nano-clay are surface modified with a coupling agent and grafted onto the side chains of the PLA to enhance the compatibility between the reinforcements and the PLA, and to improve the mechanical properties of the PLA. Moreover, ammonium polyphosphate (APP) and expandable graphite (EG) are added as flame-retardants. The results show that the UL-94 flame test of the composites achieves a V-1 or V-0 grade according to the different composition of the flame-retardants. SEM analysis reveals that the interfacial adhesion of the composite is effectively enhanced after the surface modification of the fiber. The increments of tensile and impact strengths of the composites reach 14.5% and 5.5%, respectively. Thermal analyses show that the thermal stability is significantly improved, and the increment of heat distortion temperature can reach 102%. The resulting green composites are not only flame retardant, but also have good thermal and mechanical properties.

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