Exploring the synergistic effects of surfactant combinations on the microstructure and properties of phenolic foam

This study examines how the chemical structure of surfactants and the mix of emulsifiers affects the properties of phenolic foams through bubble growth, collision, and combination during production. Two classes of surfactants were utilized: nonionic (Tween80) and anionic (sodium and ammonium lauryl sulfates). Tween80 produced low-density foam, but its combination with anionic surfactants significantly increased density by ∼270%. Variations in surfactant proportions impacted the foam's microstructural characteristics, resulting in open or closed-cell structures depending on the hydrophilic-lipophilic balance (HLB). Higher HLB values led to closed-cell morphologies, while its values in the range from 9 to 11 improved micelle formation and bubble production, resulting in open-cell structures. The combinations of emulsifiers exhibited an intermediate HLB effect that influenced foam compressive properties, ultimately affecting water compatibility.