Modification of lignin and its application as char agent in intumescent flame‐retardant poly(lactic acid)

Abstract

Urea-modified lignin was prepared according to the Mannich reaction and well characterized by Fourier transform infrared spectrometer, elemental ananlyses, and scanning electron microscopy (SEM). Ammonium polyphosphate (APP) and urea-modified lignin were added into poly(lactic acid) (PLA) as a novel intumescent flame-retardant (IFR) system to improve flame retardancy of PLA. The flammability of IFR-PLA composites was studied using limiting oxygen index, UL-94 vertical burning method and cone calorimeter test, and their thermal stability was evaluated by thermogravimetric analysis. The results showed that the urea-modified lignin combined with APP exhibited much better flame retardancy and thermal stability than that of the combination of virgin lignin and APP. The improvement may be attributed to the better char morphology with more phosphoric char evidenced by SEM and X-ray photoelectron spectroscopy.

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

“…In fact, the binary combinations of metallic phytates allow reaching a V-2 rating except for PLA/10 Na-Phyt/10 Al-Phy which burns completely after the second flame application. For sake of comparison, V-2 rating is the classification obtained for PLA fire proofed with 23 wt% of APP [16] or with 40 wt% of the classical intumescent system APP/PER (3:1) [10].…”

“…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.…”

Mechanical and Thermal Properties of Toughened Poly(L-lactic) Acid and Lignin Blends

“…Currently, due to the rapid decrease of petroleum energy sources and environmental pollution coming from petroleum-derived plastics, biodegradable and biobased polymers have received extensive interest as an alternative to conventional petroleum-based plastics (Tawakkal et al 2012;Zhang et al 2013;Zhang et al 2012). Among the degradable polymers, only a few aliphatic polymers, such as poly(lactic acid) (PLA), poly(ɛ-caprolactone)(PCL), poly[(butylenesuccinate)-co-(butylene adipate)], and polyhydroxyalkanoates, are now commercially available around the world (Li et al 2003).…”

Flame retarded poly(lactic acid): A review

“…However, the high water uptake/solubility of the conventional charring agent pentaerythritol (PER) disqualified its use for durable and engineering applications [40]. Thus, the development of environmentally friendly carbonization agents that can replace PER in IFR is the focus of current studies.…”

“…These results underline the fact that the formation and structure of the intumescent layer is a key parameter to protect the material beneath because it limits the heat and mass transfers when IFR/polymer formulations are burned. Zhang et al [40] prepared urea-modified lignin (UM-Lig) according to the Mannich reaction and added ammonium polyphosphate (APP) as a novel IFR to PLA. The PLA/UM-Lig/APP composite successfully achieved V-0 in the UL-94 vertical burning test, with a LOI value of 34.5%, and with a sharp decrease in PHRR and THR in the CCM test.…”