Intumescent-Grafted Bamboo Charcoal: A Natural Nontoxic Fire-Retardant Filler for Polylactic Acid (PLA) Composites

Abstract

In this work, an alternative flame-retardant filler based on phosphate-and urea-grafted bamboo charcoal (BC-m) at 10−30 wt % addition was aimed at improving the flame retardancy of polylactic acid (PLA) composites. The filler caused only a small reduction in strength properties but a slight increase in the modulus of elasticity of PLA composites. BC-m significantly improved the flame-retardant performance compared with pure BC. The limiting oxygen index (LOI) was 28.0 vol % when 10 wt % of BC-m was added, and 32.1 vol % for 30 wt % addition, which was much greater than the value of 22.5 vol % for 30 wt % pure BC. Unlike pure BC, adding BC-m at 20 wt % or more gave a UL-94 vertical flame test rating of V-0 with significantly reduced melt dripping. The peak heat release rate (pHRR) and total heat release (THR) of BC-m/PLA composites decreased by more than 50% compared with pure PLA, and the values for 20% BC-m were significantly less than that for 25% BC addition. The grafted biochar-based system provides an effective flame retardancy effect by a condensed-phase protective barrier through the rapid formation of a dense, honeycomb-like cross-linked carbonized char layer. The results suggest a promising route to enhancing the flame-retardant properties of biodegradable polymer composites using nontoxic, more environmentally friendly grafted biochar.

Fabrication of Phytic Acid/Urea Co-Modified Bamboo Biochar and Its Application as Green Flame Retardant for Polylactic Acid Resins

“…Moreover, dripping could only be observed for the relatively lower addition (5 wt%) of mBC to the composite, and the cotton underneath did not catch fire; the remaining composites all achieved a V-0 level when mBC was dosed at 10 wt% or beyond, and the dipping was also constrained. The LOI and UL-94 results both outperformed the BC/PLA and BC-m/PLA composites [ 40 ]. With reference to the BC-m/PLA composites, they were reported to be prepared through phosphorous acid and urea with almost same modification conditions, except for microwave assistance.…”

“…A bio-based, core–shell flame retardant (APP@CS@ATMP) is designed to achieve excellent flame-retardant and antidripping properties of PLA composites [ 39 ]. Zhang et al [ 40 ] employed a microwave-assisted modification method to prepare phosphorous acid/urea-based intumescent bamboo charcoal (BCm) that asserted the natural flame retardancy enhancement of BC/PLA composites; its LOI was 28.0 vol.% when 10 wt% of BCm was added, and 32.1 vol.% for 30 wt% addition, which was much greater than that of the 22.5 vol.% for BC/PLA(30/70) composite. Adding BC-m at 20 wt% or more gave a UL-94 rating of V-0 with significantly reduced melt dripping; meanwhile, its mechanical property was undermined to a certain extent but still was acceptable.…”

Mechanically Robust and Flame-Retardant Polylactide Composites Based on In Situ Formation of Crosslinked Network Structure by DCP and TAIC

“…Compared with the ADR/nano ZnO system [51], the mechanical properties of the two system are similar to those of pure PLA, which means that both crosslinked structures can achieve excellent performance. In addition, the study of Zhang [54] showed that the mechanical properties of PLA composites decreased significantly after the addition of flame retardants. The existence of crosslinking network can make the material withstand greater stress.…”

Flame retardant and antibacterial properties of PLA/PHMG‐P/APP composites

“…However, they release corrosive and toxic chemicals during combustion. [15] The search for environmentally friendly and inexpensive flame retardants has attracted increasing attention. [16][17][18][19][20][21][22] Phosphorus-nitrogen-based intumescent flame retardants (IFRs) are promising because of their remarkable fire hazard reduction, low toxicity, and low cost.…”