Synergistic effects of expandable graphite and ammonium pentaborate octahydrate on the flame‐retardant, thermal insulation, and mechanical properties of rigid polyurethane foam

Abstract

The use of flame retardants (FRs) to improve the flame retardancy but also having good insulation and mechanical properties of rigid polyurethane foam (RPUF) has become significant due to the increasing demand in both the industry and academia. In the present study, a series of RPUF composites containing expandable graphite (EG), ammonium pentaborate (APB) octahydrate, and their binary blends were prepared with one‐shot and free‐rise methods. The effects of FRs on the FR and physical‐mechanical properties of RPUFs were investigated. The results show that both EG and APB could improve the flame retardancy of RPUFs and reduced the smoke production. The FR effect of EG was better than APB and more importantly, synergistic effect was found between EG and APB. The best results were obtained by the foam in the composition of 15E and 5A. The cone calorimeter test results showed that the peak heat release rate (pHRR) and total smoke release (THR) of 15E/5A foam were lower than the foams of 20E and 20A. The pHRR and THR values of 15E/5A foam decreased about 57.5% and 42.8% compared to the neat RPUF, respectively. Total smoke production (m2) also reduced about 77.0% by 20E and 83.6% by 15E/5A foams. Thermogravimetric analysis indicates that the char residue of 15E/5A foam increased to 39.5%, which provided better flame retardancy. The foam composites have high compressive strength (105‐150 kPa) and low thermal conductivity values (19.9‐21.3 mW/mK). While the thermal conductivity of 15E/5A foam increased by 0.5%, its compressive strength increased by 6.1%.

Composites of Semi-Rigid Polyurethane Foams with Keratin Fibers Derived from Poultry Feathers and Flame Retardant Additives

“…GE works mainly in the solid phase, creating a layer of low-density char on the surface of the polymer but it also greatly reduces smoke. This is caused by the reaction of sulfuric acid with graphite flakes, which expands its volume by about 100 times, accompanied by gases generated at high temperature (CO 2 , H 2 O, SO 2 ) [ 62 ].…”

Flame Retarded Rigid Polyurethane Foams Composites Modified by Aluminum Diethylphosphinate and Expanded Graphite

“…Among them, the LOI value of RPUF/ADP10/EG20 can reach the maximum 25.9 vol%. It is worth noting that RPUF/ADP12/EG (Akdogan et al, 2020), RPUF/ADP10/EG20, RPUF/ADP7.5/EG22.5, and RPUF/ADP6/EG24 composites have greater LOI values Table 4, compared with no rating of the pure RPUF, all FR-RPUF exhibited V-1 rating, indicating the improved flame retardancy of the composites. As a simple screening method, MCC analysis was performed, where only a small amount of samples was needed to investigate the combustion of the RPFU and FR-RPUF composite .…”

“…Akdogan et al report the synergistic effect of expandable graphite (EG) and ammonium pentaborate octahydrate (APB) in RPUF composites. The flame retarded RPUF composite with 15 wt EG and 5 wt% APB loading possesses PHRR reduction of 57.5% and THR reduction of 42.8% compared with those of virgin RPUF (Akdogan et al, 2020).…”

An environmentally friendly process for preparing commercial ceramic foam composites based on frit/glass wastes

“…Compared to the polymer‐based foam used in the insulation industry due to their high pore amount, it is seen that ceramic‐based foam materials have higher mechanical, chemical, and thermal stability 17 . Polymeric foams used for insulation in the event of a possible fire are known to be largely damaged by the toxic gases released during the fire, whereas ceramic and glass‐ceramic foams are known to be nonflammable due to their inorganic nature 18,19 . In addition to these, glass foam ceramic materials are developed for insulation purposes from different waste materials as well 9‐11,20 .…”