Comparison of Toughening Effects of Various Additives on Phenolic Foam

Abstract

Phenolic foams (PFs) are considered excellent insulation materials owing to their flame retardancy and low thermal conductivity. However, their mechanical properties often lag behind those of other polymeric insulation materials. To fully exploit their properties and broaden end-use applications, the mechanical properties of PFs must be enhanced. In this study, various modifications were introduced into the PF matrix with the aim of enhancing its properties. The toughening effects of four additives: urea (U), nano clay (NC), sodium silicate (SS), and lignin (Li) were studied and compared. Changes that occurred in the density, cell morphology, thermal conductivity, compressive strength, and thermal stability after the addition of these fillers were analyzed. Both compressive strength and thermal stability increased with the inclusion of all additives, and the SS-toughened foam shows the biggest improvement. Li and NC addition resulted in a 34% improvement in compressive strength, while SS and U addition displayed increases of 52 and 11%, respectively. SStoughened PF shows greater improvements in all of the important properties compared with those of the other toughened foams. Several PFs were prepared by changing the SS concentration to optimize the formulation, which yielded improvements in properties. The effects of SS concentration on density, thermal conductivity, and compressive strength were studied. The formulation with 0.37% sodium silicate concentration (PF-SS1) shows a 15% improvement in mechanical properties.

Preparation and Characterization of Date Palm Bio-Oil Modified Phenolic Foam

“…In the physical toughening method, organic or inorganic materials, fibers, and glass are blended into the phenolic resin prior to curing. Our recent paper compares the toughening effect of various additives such as urea, nano clay, sodium silicate, and lignin on phenolic foam [6]. The chemical modification method is preferred to physical toughening as it tends to provide better improvements in mechanical properties.…”