Synergistic Flame Retardant Effects of Expandable Graphite and Ammonium Polyphosphate in Water-Blow Polyurethane Foam

Abstract

In this research, expandable graphite (EG) and ammonium polyphosphate (APP) were incorporated into water-blow semirigid polyurethane foam (SPUF) as flame retardants. The synergistic flame retardant effects of EG with APP in SPUF had been studied by thermogravimetric analysis (TGA), limiting oxygen index (LOI), horizontal burning test, polarizing microscope, and scanning electron microscopy (SEM). The results indicated that APP and EG used together in SPUF could effectively improve the flame retardancy of SPUF. When the EG to APP ratio reached 2 : 1 under the total content of flame retardants was kept constant as 20%, the LOI value was increased by about 51% compared to pure SPUF, 2.9% to SPUF/EG and 16.3% to SPUF/APP. Besides, the residual char was increased up to 27.7% displayed by TG test results. SEM shows that burned residues of EG/APP/SPUF present more compact char and worm-like structure. Furthermore, EG shows negative effect on the mechanical property of SPUF with 21.7% decrease in compression modulus, but the mechanical property can be improved by the addition of appropriate content of APP.

Intumescent polypropylene: Interactions between physical and chemical expansion

“…This paper examines interactions and possible synergies between these two modes of action of intumescence: physical expansion with EG and chemical expansion with AP. Indeed, synergistic effects between these two components were already demonstrated in different materials, such as polyurethane foams, 14 wood‐PP composites, 15 jute‐PP composites, 16 poly (butylene terephthalate), 17 polylactide, 18 or acrylonitrile‐butadiene‐styrene resin 19 . This work focuses on PP.…”

It Takes Two to Tango: Synergistic Expandable Graphite–Phosphorus Flame Retardant Combinations in Polyurethane Foams

“…One of the champions among the currently proposed flame retardants that has found application in today's products is the synergistic combination of expandable graphite (EG) with a phosphorous flame retardant (P-FR). This approach has become legendary for the excellent flame retardancy it provides to polyurethane foams (PUFs) [11][12][13][14]. In this feature article, we turn the scientific spotlight on the concept, mechanisms, and role of Polymers 2022, 14, 2562 2 of 24 the synergistic combinations of EG and P-FRs in PUFs in order to evoke the applause this approach deserves [15][16][17][18].…”

Influence of the Expandable Graphite on the Thermal properties of a Rigid Polyurethane Foam for construction

“…When subjected to heat, these inserted molecules degrade with the evolution of gas, the foaming occurs, and the layer thickness increases by 100 times. Typically, EG is used in combination with phosphorus compounds, antimony oxides, or metal hydroxides, which act as a substrate for the layer of expanded graphite [10][11][12][13][14][15].…”