Establishment of a highly efficient flame-retardant system for rigid polyurethane foams based on bi-phase flame-retardant actions

Abstract

Rigid polyurethane foam (PU), one of the most promising wall insulation materials, exhibits high flammability and fire risk. In this work, PU/EG/HQ composites with highly effective flame retardancy were fabricated by adding two kinds of flame retardants, expandable graphite (EG) and 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphorylphenanthrene-10-oxide (DOPO-HQ), during the synthesis of polyurethane. Thermal stability and flammability were evaluated using the limiting oxygen index (LOI), thermogravimetric analysis (TGA), UL-94 vertical flame results, and cone colorimeter tests. The as-synthesized PU/EG/HQ composites showed a high LOI value, a maximum peak heat release rate (PHRR) value which was decreased by 58.5% and an increased char yield at 800 C. They also achieved UL-94 V-0 classification.SEM and Raman spectra indicated that the "worm-like" intumescent char layer with a graphitized structure and the formed viscous liquid film were vital factors in the enhancement of the flame retardancy of polyurethane foam in the condensed phase. TG-IR results show that the release of toxic volatiles and flammable gases from the PU/EG/HQ samples was remarkably decreased compared with the release from pure PU. This work associates a gas-solid biphase flame retardancy mechanism with the incorporation of two types of flame retardant and presents an effective method for the synthesis of bi-phase flame-retardant polymers.

Synergistic effects of aluminum hydroxide, red phosphorus, and expandable graphite on the flame retardancy and thermal stability of polyethylene

“…The voluminous char layers protect the composite by preventing heat/mass transfer. Moreover, the expansion of EG can absorb heat efficiently, thus cooling down the composite material 38 . In the case of ATH, its endothermic dehydration releases water and thermally stable aluminum oxide on the surface of the composite, which protects the underlying LDPE matrix 36 .…”

Effects of Tung Oil-Based Polyols on the Thermal Stability, Flame Retardancy, and Mechanical Properties of Rigid Polyurethane Foam

“…RPUF has been widely used in materials for building insulation due to its excellent mechanical performance. However, a limitation to the use of RPUF is flammability, which is related to its cellular structure and low density [7,8].…”

Structure and Flame-Retardant Actions of Rigid Polyurethane Foams with Expandable Graphite

“…When considering the situation, researchers conducted lots of investigations regarding how to promote RPUF’s the flame retardancy performance. In general, two methods were mainly adopted [6,7,8,9]. One way was adding the non-reactive flame retardant [10], which was confirmed to be a simple and effective approach to improve the flame resistance.…”