Density Effect on Flame Retardancy, Thermal Degradation, and Combustibility of Rigid Polyurethane Foam Modified by Expandable Graphite or Ammonium Polyphosphate.

Yang Yang,Wan Wan,Jiang Jiang,Liu Liu,Chen Chen

doi:10.3390/polym11040668

Abstract

The current study aims at comparatively investigating the effect of apparent density on flame retardancy, thermal degradation and combustion behaviors of rigid polyurethane foam (RPUF), RPUF/ expandable graphite (EG) and RPUF/ ammonium polyphosphate (APP). A series of RPUF, RPUF/EG and RPUF/APP samples with different apparent densities (30, 60 and 90 kg/m3) were prepared. The flame retardancy, thermal degradation, and combustion behaviors of each sample were investigated. Limiting oxygen index (LOI) results indicated that increasing apparent density was beneficial to the flame retardancy of all foam systems. The effect of apparent density on the enhancement of flame retardancy followed the sequence of RPUF < RPUF/APP < RPUF/EG. Thermogravimetric analysis (TGA) results showed that an increase in the apparent density can cause more weight loss in the first degradation stage and less weight loss in the second degradation stage for all foam systems. The combustion behaviors also showed significant differences. The samples with a higher apparent density showed a longer duration of heat release and higher total heat release (THR). The findings in this study demonstrated that apparent density played an important role in flame retardancy, thermal degradation, and combustion behaviors of RPUF, which must be paid more attention in the studies of flame-retardant RPUF.

Highlights

Rigid polyurethane foam (RPUF), one of the most broadly used organic thermal insulation materials, has a bright future because of its multiple merits such as low thermal conductivity, light weight, low permeability, excellent mechanical performance, and convenience construction, etc. [1,2,3,4].it has significant fire hazards when used as building external wall insulation material due to its high flammability
Behavior of pure rigid polyurethane foam (RPUF) indicated that the increase of apparent density of foam was beneficial to the flame retardancy of RPUF, but the Limiting oxygen index (LOI) increment is limited, which is in good agreement with the report of Bian and his coauthors [34]
The effect of apparent density on flame retardancy, thermal degradation, and combustion behaviors of RPUF, RPUF/expandable graphite (EG) and RPUF/ammonium polyphosphate (APP) were investigated in this paper

Summary

Introduction

Rigid polyurethane foam (RPUF), one of the most broadly used organic thermal insulation materials, has a bright future because of its multiple merits such as low thermal conductivity, light weight, low permeability, excellent mechanical performance, and convenience construction, etc. [1,2,3,4].it has significant fire hazards when used as building external wall insulation material due to its high flammability. Rigid polyurethane foam (RPUF), one of the most broadly used organic thermal insulation materials, has a bright future because of its multiple merits such as low thermal conductivity, light weight, low permeability, excellent mechanical performance, and convenience construction, etc. Enhancing the fire safety of RPUF is an important subject. The halogen-containing RPUF would release corrosive products and toxic gases during combustion, which are harmful to escape, and poisonous to the environment. It is imperative to research the halogen-free flame-retardant systems of RPUF [3,4,5,6,7,8]

Methods

Results

Conclusion