Preparation of lignin–silica hybrids and its application in intumescent flame-retardant poly(lactic acid) system

Abstract

Lignin–silica hybrids (LSHs) were prepared by sol–gel method and characterized by Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). LSH and ammonium polyphosphate (APP) were added into poly(lactic acid) (PLA) as a novel intumescent flame-retardant (IFR) system to improve the flame retardancy of PLA. The flame-retardant effect of APP and LSH in PLA was studied using limiting oxygen index (LOI), vertical burning (UL-94) tests and cone calorimeter. The thermal stability of PLA/APP/LSH composites was evaluated by thermogravimetric analysis (TGA). Additionally, the morphology and components of char residues of the IFR-PLA composites were investigated by SEM and XPS. With the addition of APP/LSH to PLA system, the morphology of the char residue has obviously changed. Compared with PLA/APP and PLA/APP/lignin, a continuous and dense intumescent charring layer with more phosphor in PLA composites is formed, which exhibits better flame retardancy. All the results show that the combination of APP and LSH can improve the flame-retardant property and increase the thermal stability of PLA composites greatly.

Preparation of lignin-based silica composite submicron particles from alkali lignin and sodium silicate in aqueous solution using a direct precipitation method

“…Recently, some researchers were beginning to try to incorporate lignin with silica by the precipitation method or sol-gel process, but the contents of lignin in the lignin/silica composites were very low (Hayashi et al, 1997;Qu et al, 2010;Zhang et al, 2013). Meanwhile, the composites were severely agglomerated (Zhang et al, 2012;Saad and Hawari, 2013). Jesionowski et al (2014), Klapiszewski et al (2012Klapiszewski et al ( , 2013aKlapiszewski et al ( ,b, 2014 and Nowacka et al (2013) had done a lot of studies on SiO 2 /lignin composites in the past years.…”

Intumescence: Tradition versus novelty. A comprehensive review

“…M a n u s c r i p t 41 Indeed, APP is usually employed in joint action with melamine eventually coupled with nanofillers like organo-modified montmorillonites, MWNTs [277], organo-modified zinc aluminium layered double hydroxide (Zn-Al LDH) [278], zirconium phosphate [279], expandable graphite [280], β-CD [89] and poly(pseudorotaxanes) [90], starch [281][282][283], or lignin-silica hybrids from sol-gel processes [284]. APP has been also combined with a simple poly(ethylene glycol) [285].…”

Metallic phytates as efficient bio-based phosphorous flame retardant additives for poly(lactic acid)

“…The fire performances of the blend were improved with the increasing amount of phosphorus content. The use of biosourced char-forming agents, such as lignin, starch or β-cyclodextrin, in PLA has been studied as a way to develop more environmentally friendly materials [9][10][11][12][13][14][15][16][17][18]. Reti et al [14] evaluated the efficiency of intumescent formulations containing ammonium polyphosphate (APP) combined with different carbonization agents.…”