The Influence of Fly Ash on the Foaming Behavior and Flame Retardancy of Polyurethane Grouting Materials

Abstract

Polyurethane (PU) grouting material has been widely utilized to control water inrush in mining fields. However, the application has been limited by its high cost and poor flame retardancy. Here, we use the fly ash (FA), a waste from coal of the iron-making industry and power plants, as a partial replacement of conventional filler in PU grouting materials to reduce the production cost and the environmental pollution of FA. The surface-modified FA-filled PU (PU/FA) composites were prepared by room-temperature curing. The effects of FA contents (φ) on the structure, foaming behavior, thermal stability, mechanical properties, hydrophobic properties, and flammability of PU grouting materials were examined. Results showed that the higher the φ, the more porous the PU/FA composites are, resulting in a lower density and lower mechanical properties. The relationship between the compression modulus E and the density ρ of the PU/FA composites was E ∝ ρ1.3. In addition, the surface-modified FA improved the compatibility between the hard and soft segment of PU in the PU/FA composite, giving the composites enhanced thermal stability, high hydrophobicity, and flammability resistance.

Fly Ash-Incorporated Polystyrene Nanofiber Membrane as a Fire-Retardant Material: Valorization of Discarded Materials

“…The Fe 2 O 3 present in FA forms a dense char layer by promoting the crosslinking of the polymer [ 57 ]. The strong interaction between FA particles and PS nanofibers promotes the heat resistance of the composite membrane, thereby enhancing the overall fire-retardant properties [ 58 , 59 ].…”

Polymer Composite Analysis and Characterization

“…A fifth article on flame-retardant materials was included in this Special Issue. The paper by Sitong Zhang et al entitled "The Influence of Fly Ash on the Foaming Behavior and Flame Retardancy of Polyurethane Grouting Materials" [5] studied the improvement in flame-retardant properties in polyurethane (PU) grouting material. The authors used fly ash (FA) as surface-modified polyurethane (PU/FA) fillers.…”

Polyurethane Exothermic Polymerization and Phase Change Material Thermal Delay Matching: An Approach to Reducing Fire Risks in Mining Polymer Materials

“…Currently, scholars’ research on polyurethane materials mainly focuses on the enhancement of their mechanical properties − and flame resistance − by incorporating inorganic fillers. Pei created corrosion-resistant PU/cellulose nanocrystal composites with noticeably better tensile strength and modulus by using cellulose nanocrystals to boost the effective cross-linking density of the elastomer network; Mustafov constructed porous three-dimensional PU-based chitosan with hydroxyapatite and diatomaceous earth as fillers.…”