Grafting cellulose nanocrystals with phosphazene-containing compound for simultaneously enhancing the flame retardancy and mechanical properties of polylactic acid

Abstract

Cellulose nanocrystals (CNCs) have been used as bio-based carbon source in intumescent system. However, CNCs have the disadvantages of low onset decomposition temperature and decompose and carbonize during processing. We, herein, demonstrated the design of phosphazenecontaining CNCs (P/N-CNCs) with great thermal stability and outstanding charring ability. The TGA results showed that the initial decomposition temperature of P/N-CNCs was increased from 202.4 ℃ to 272.2 ℃ (increased by 34.5%), and the residual char at 700 ℃ was increased from 24.9 wt% to 55.8 wt% compared with CNCs. Then, ame retardant PLA composites were prepared by blending PLA, P/N-CNCs with ammonium polyphosphate (APP), melamine (MPP), aluminum hypophosphite (AHP) and piperazine pyrophosphate (PPAP), respectively. The thermal stability, ame retardant properties and mechanical properties of PLA composites were investigated. The results showed that the ame retardant system constructed by 7 wt% APP and 3 wt% P/N-CNCs had the best effect in PLA. PLA/7APP/3P/N-CNCs had the highest limit oxygen index value (28.1%), the lowest peak heat release rate (266 kW/m 2 ) and reached UL 94 V-0 rating. Moreover, the tensile strength, impact strength and elongation at break of PLA/7APP/3P/N-CNCs were increased by 7.3%, 18.6% and 29.4%, respectively, compared with these properties of PLA/7APP/ 3CNCs. This work provides a new idea for the design of CNCs with great thermal stability and outstanding charring ability, and offers a new method for the preparation of high-performance ame-retardant PLA composites.

Super-efficient fire safety poly(lactide) enabled by unique radical trapping

“…Moreover, the LOI result of PLA containing 10% modification with FR cellulose nanofiber reached 25.8% and the UL-94 V-0 grade was achieved. 16 At the same time, He et al 17 reported that the LOI result of PLA with 10 wt% phosphazene-containing cellulose nanocrystals and APP reached 28.1% and the UL-94 V-0 grade was obtained. Wang et al 18 investigated the LOI result of PLA with 30% APP and starch which was found to reach 41.0% and the UL-94 V-0 grade was achieved.…”

“…Recently, sustainable biological FR additives, such as lignin, [10][11][12][13][14] cellulose, [15][16][17] starch, 18,19 chitosan (CS), [20][21][22][23] protein, 24 b-cyclodextrin (CD), 25,26 polydopamine (PDA), 29 phytic acid (PA), [30][31][32][33] vegetable oils, furan (FA) [35][36][37] etc. have become a hot and attractive topic.…”

Effect of electrospun stereocomplex PLA fibers and modified cellulose nanocrystals on crystallization of poly(L‐lactic acid)

“…33,34 Therefore, surface modification of CNCs is widely adopted to enhance the hydrophobicity thus the dispersion state of CNCs in polymer matrix would be significantly improved. [35][36][37][38][39] In this study, electrospun stereocomplex PLA fibers (Sc-fibers) and PLLA grafted cellulose nanocrystals (g-CNCs) were prepared as nano-fillers and then blended with PLLA matrix to investigate the crystallization and mechanical properties of PLLA. For comparison, a PLLA nanocomposite containing Sc-fibers and g-CNCs, respectively was also prepared.…”

Synergistic flame retardant effect of aluminum hydroxide and ammonium polyphosphate on epoxy resin

“…33,34 The dense char layer formed by the condensed phase reaction is primarily responsible for its effect. [35][36][37][38][39][40][41] For example, in epoxy resin, APP and activated carbon-supported Fe 2 O 3 inhibited decomposition and promoted the formation of a stable char layer, effectively improving the flame retardancy of the matrix. 42 Hydroxide flame retardant additives such as aluminum hydroxide (ATH), magnesium hydroxide (MH), and layered double hydroxides (LDHs) are inexpensive, nontoxic, smoke-free, and halogen-free.…”

“…Furthermore, APP is used as an effective intumescent flame retardant in a variety of polymers 33,34 . The dense char layer formed by the condensed phase reaction is primarily responsible for its effect 35–41 . For example, in epoxy resin, APP and activated carbon‐supported Fe 2 O 3 inhibited decomposition and promoted the formation of a stable char layer, effectively improving the flame retardancy of the matrix 42 …”