A novel intumescent flame‐retardant LDPE system and its thermo‐oxidative degradation and flame‐retardant mechanisms

Abstract

A carbonization agent, 3,9-di (2-hydroxyisopropyl)-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]-undecane (SPEPO), was synthesized from pentaerythritol (PER), phosphorus trichloride, formic acid, and acetone as raw materials. The structure of SPEPO was characterized by FTIR and 1 H-NMR. As a carbonization agent and an acid source, SPEPO can form a novel intumescent flame-retardant (IFR) system for low density polyethylene (LDPE) together with ammonium polyphosphate (APP) and melamine phosphate (MP). The flame retardancy and thermal behavior of the IFR system for LDPE were investigated by limiting oxygen index (LOI), UL-94 test, and thermogravimetric analysis (TGA). When the weight ratio of SPEPO, APP, and MP is 7:7:1 and their total loading level is 30%, the IFR-LDPE presents the optimal flame retardancy (LOI value of 27.6 and UL-94 V-0 rating). However, SPEPO, APP, or MP can only show a very poor flame-retardant performance when used alone. This indicates that there is a synergistic effect among SPEPO, APP, and MP. TGA results obtained in air demonstrate that SPEPO has an ability of char formation itself, and the char residue of SPEPO can reach 24 wt% at 700-C. The IFR can change the thermal degradation behavior of LDPE, enhance T max of the decomposition peak of LDPE, and promote LDPE to form char based on the calculated and the experimental data of residues. According to the results of Py-GC/MS in combination with FTIR of the char residues at different temperatures, a possible flame-retardant mechanism has been proposed.A novel intumescent flame-retardant LDPE system 1573 Scheme 4. A speculative route for char formation of PEDP.Scheme 5. The reaction of oxidized PE chain with PEDP and polyphosphoric acid.

Flame Retardation of Natural Rubber: Strategy and Recent Progress

“…In current research, phosphorus/nitrogen (P/N) flame retardants are considered to be one of the most important systems to achieve highly efficient halogen-free flame retardance of polymers [38,39]. Among the P/N system, intumescent flame retardants (IFR) have been paid much attention in the past ten years due to their high flame-retarding efficiency [40].…”

Hybridization of α-zirconium phosphate with hexachlorocyclotriphosphazene and its application in the flame retardant poly(vinyl alcohol) composites

“…For PVA/HAC3 (as shown in Fig. 6e-f), the thick, compact, continuous char layers without pores appear on both sides of residual chars, which could provide a good barrier to the inhibition of heat, mass and flammable pyrolysis gases transferring between the flame zone and the substrate during fire test, thus protecting the underlying materials from further burning and pyrolysis [35,36]. This morphology may be caused by the synergistic effect between IFR modifiers and α-ZrP plates, the former affording a solid acid sites barriers and volatilized in the early degradation stage, and the latter catalyzing the cross-linking of PVA chains during combustion, and furthermore, strengthening the char barriers to make it more intact and robust to display planar inhibition function, thus to improve the flame retardancy at higher temperature.…”

Synthesis of novel intumescent flame retardant containing phosphorus, nitrogen and boron and its application in polyethylene

“…Unfortunately, some halogen-containing compounds have been forbidden for use in many public places due to the release of toxic and corrosive gases which can choke people exposed to the fumes. The gases also corrode the metal equipment and pollute the environment [7][8][9][10][11]. Environment protectors have resisted the large-scale use of halogen-containing flame retardants and advocated the wide application of alternative chemical products [12].…”