Synergistic effect of aluminum hydroxide and expandable graphite on the flame retardancy of polyisocyanurate–polyurethane foams

Abstract

For the first time, expandable graphite (EG) and aluminum hydroxide (ATH) was combined to improve the flame retardancy of polyisocyanurate-polyurethane (PIR-PUR) foam. The limited oxygen index increased from 26.5 for the PIR-PUR matrix to an incredible value of 92.8 when 24 phr (parts per 100 of matrix) EG and 60 phr ATH were incorporated into the matrix. Based on morphology observation and thermogravimetric analysis, it was speculated that two factors contributed to the improvement of flame retardancy primarily. First, ATH could effectively induce "villi" like particles, which was useful to form a dense char. The compact char layer could effectively impede the transport of bubbles and heat. Second, ATH and EG accelerated the initial degradation and fluffy char was quickly generated on the surface of the composites. Thus, the degradation of the composite was slowed down and the diffusion of volatile combustible fragments to flame zone was delayed.

Effects of hydrotalcite on rigid polyurethane foam composites containing a fire retarding agent: compressive stress, combustion resistance, sound absorption, and electromagnetic shielding effectiveness

“…7(d-f), the dense carbon protective layer caused by the hydrotalcite and the re retarding agent during combustion forms an intumescent protection to refrain the transmission of heat and mass from the polymer matrix to the heat source preventing further decomposition. 34 Excessive hydrotalcite forms spherical object covering the cells during the combustion, protecting the underneath matrix. Fig.…”

Preparation and characterization of highly thermostable polyisocyanurate foams modified with epoxy resin

“…A great effort has been made to improve the physicochemical properties of PUR–PIR foams. Boro‐organic compounds, borate, aluminum hydroxide, expandable graphite, phosphonates, and zinc salts are used as fillers to improve the thermal and flame retardance of PUR–PIR foam . However, a low content of fillers gives rise to limited improvement of flame retardancy, whereas a high content causes high viscosity and poor mechanical properties …”

Diphase flame‐retardant effect of ammonium polyphosphate and dimethyl methyl phosphonate on polyisocyanurate‐polyurethane foam

“…The research of halogen‐free flame‐retardant PIR‐PUR foams were mostly about expandable graphite (EG) or its synergistic system with triethyl phosphate, red phosphorus, aluminum hydroxide, and ammonium polyphosphate (APP) . EG possessed high flame‐retardant efficiency for PIR‐PUR foam.…”