Effect of expandable graphite on the properties of intumescent flame‐retardant polyurethane foam

Abstract

Water-blown rigid polyurethane foam (PUF) with two different particle sizes (180 and 300 lm) of expandable graphite (EG) as a flame-retardant additive were prepared, and the effects on the mechanical, morphological, water absorption, thermal conductivity, thermal, and flame-retardant properties were studied. In this investigation, EG content was varied from 5 to 50 php by weight. The mechanical properties of PUF decreased with increasing EG loading in both cases. The water absorption of the PUF increased with an increase in the EG loading mainly because of the collapse of foam cells, as evidenced from the scanning electron microscopy pictures. The thermal conductivity of the EG-filled PUF showed that the insulation properties decreased with EG loading. The flame-retardant properties (limiting oxygen index and char yield measurement) of the PUF improved with increasing EG loading. PUF filled with the higher particle size EG showed better mechanical properties and fire-retardant properties than the PUF filled with the lower particle size EG.

The pyrolysis behaviors of polyimide foam derived from 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride/4,4′‐oxydianiline

“…[10][11][12][13][14][15][16][17][18] Decomposition reaction order of polyimide is not the first order. And the main pyrolysis products of polyimide are CO, CO 2 , and H 2 O. The foaming agents and additives in PI foam perhaps have effect on pyrolysis behaviors and products.…”

“…The long-term service temperatures of most common polymeric foams are lower than 200 o C, and 5% weight loss temperatures are lower than 450 o C in air. [1][2][3] The long-time service temperatures of PI foams are higher than 200 o C. The glass translation temperatures of some PI foams are higher than 300 o C. Therefore, PI foam has been applied as thermal and acoustic insulation materials in the fields of aerospace and navigation, which may be due to its high and low temperature resistance, low smoke, low toxicity, low volatile, no halogen, no ozone consumption, easy installation, and so on. [4][5][6][7][8] But, PI foam will degrade rapidly at more than 500 o C. In reusable launch vehicle (RLV) mission from launch to orbit and to reentry, the surface temperature of PI foam used as thermal protection system (TPS) will increase rapidly in short time and PI foam will degrade or fall off.…”

Preparation of Boric Acid Modified Expandable Graphite and Its Influence on Polyethylene Combustion Characteristics

“…EG is known as a new generation of intumescent flame retardant (IFR) for its good capability of halogen-free, non-dropping and low-smoke. 3,4 This retardant acts in both the condensed and gas phase through an endothermic reaction: 5,6 (1) when contacting with flame source, EG will instantly expand and turn into swollen multicellular "graphite worms" covering on the retarded polymer surface, which is in favor of slowing down the heat and mass transfer and interrupting the degradation of polymer matrix. (2) In oxidation reaction with H 2 SO 4 at high temperature, it releases gases such as CO 2 , H 2 O and SO 2 , 3, 7-9 which can reduce concentration of combustible gas; thereby char formation has been enhanced.…”

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

“…21 The second degradation stage at 400-800 C is primarily the degradation of substituted urea resulting from the reaction of carbodiimide with alcohol or water. 22 In the presence of EG, both the T 5% and the T max1 of the PU/EG composites are shied to a lower value compared with pure PU and decrease with increasing EG loading. This may be caused by the early degradation of EG with a T max1 value of 220.1 C (shown in Fig.…”