Flame retardancy of hollow glass microsphere/rigid polyurethane foams in the presence of expandable graphite

Abstract

Rigid polyurethane foams (RPUF) filled with various loadings of expandable graphite (EG) or/and hollow glass microspheres (HGM) were prepared by cast molding. The flame retardant properties of these composites were investigated by limiting oxygen index (LOI), horizontal and vertical burning tests. The composite with 10 wt % HGM and 20 wt % EG had the best flame retardant properties, and its LOI value reached 30 vol %. The addition of an appropriate loading of HGM improved the compressive strength and modulus of RPUF and EG/RPUF. When the HGM content arrived at 10 wt %, the compressive strength and modulus of the composites reached the maximum value. The dynamical mechanical analysis (DMA) showed that the addition of EG and HGM made the glass transition temperature shift to a higher temperature, and 10 wt % EG and 10 wt % HGM filled RPUF had the highest storage modulus. The scanning electronic microscope (SEM) observation indicates that the additives led to the decrease in the cell size. In addition, the flame retardant mechanism, the thermal properties, the burned surfaces and the interface surfaces were elucidated.

Effects of inorganic fillers on the flame‐retardant and mechanical properties of rigid polyurethane foams

“…Thermal degradation test has been used by Xian‐Yan Meng and his fellows for demonstrating that the addition of EG to RPUF could lead to an increase of the amount of high‐temperature residues but a drop of the compressive strength . To make up the loss of mechanical properties caused by EG, Xiang‐Cheng Bian's group studied the RPUF added both EG and HGM, and found the resulting RPUF composites had the same flame retardancy but a better mechanical properties compared with the EG/RPUF . However, only adding HGM cannot make a significant improvement to the compressive strength.…”

Expandable graphite‐methyl methacrylate‐acrylic acid copolymer composite particles as a flame retardant of rigid polyurethane foam

“…The detailed preparation procedures of RPUF were reported in our previous publications 5–9. The pEG‐P(MA)/RPUF and P(MA)/RPUF composites were prepared using the same way by cast molding.…”

“…In our previous work, we studied the influence of various factors (the loading of EG, the density of PUF, and the size of EG particles) on the flame retardant and mechanical properties of the EG‐filled rigid PUF (RPUF) 5–9. It has been verified that EG could effectively improve the fire retardant performance of RPUF.…”

Synergistic effect of expandable graphite and aluminum hypophosphite on flame‐retardant properties of rigid polyurethane foam

“…Rigid polyurethane foam (RPUF) is a kind of structure and thermal insulation material, which can withstand a certain load without obvious deformation. It is extensively used in various fields, such as construction, transportation, petrochemical engineering, aeronautics, and astronautics due to its low density, high compressive strength, superior dimensional stability, lower thermal conductivity, and good cohesiveness . However, pure RPUF is flammable because it consists of a large number of aliphatic segments and possesses a porous cellular structure .…”