Preparation and properties of nano ZnO toughed phenol–urea‐formaldehyde foam

Abstract

Urea formaldehyde (UF) and phenol formaldehyde (PF) foam possess outstanding flame-retardant properties, excellent insulation, and low thermal conductivity. These properties make them suitable for thermal insulation in buildings. However, the mechanical properties still need to be improved. In this study, orthogonal test was designed to optimize the level components of PF/UF composite foam first, then nano ZnO was added to the PF/UF composite foam to improve its toughness. The effects of nano ZnO on the morphology, apparent density, pulverization rate, thermal conductivity and thermal degradation property, flame retardancy, and mechanical properties of the ZnO/PF/UF nanocomposite foam were studied. The addition of nano ZnO improved the bending and compressive strength and decreased the pulverization rate of the composite foam significantly. The ZnO/PF/UF nanocomposite foam also presented better flame retardant properties than PF/UF composite foam. The largest oxygen index values of ZnO/PF/UF nanocomposite foam could reach 39.31%, while the thermal conductivity and the maximum rate of weight loss temperature were increased to 0.036 W/(mÁK) and 279 C, respectively. Moreover, ZnO/PF/UF nanocomposite foam showed low apparent density property (0.27 g/cm 3). K E Y W O R D S composites, foams, mechanical properties, nanoparticles, thermosets 1 | INTRODUCTION At present, the thermal insulation materials used in building mainly include organic thermal insulation materials and inorganic thermal insulation materials. Organic insulation material (polymer foam material) is a microporous material made from polymer matrix filled with gas, which presents low density, low water absorption, high porosity, and excellent insulation performance. 1-3 Thus, it is widely used in the construction industry owing to excellent flame retardancy, chemical resistance, environmental friendly, thermal insulation, low price, and low water absorption. Urea formaldehyde (UF) foam and phenol formaldehyde (PF) foam has been extensively promoted as the most suitable alternative for thermal insulation building materials. 4-8 However, UF foam lacks active functional groups, thus, it always presents high brittleness, high pulverization ratio, low strength, and toughness. Meanwhile, PF foam also suffers from some mechanical weaknesses. For these reasons, it is necessary to focus on the improvement of PF/UF composite foam mechanical properties, such as, compressive and bending strength, friability and pulverization rate, while still maintaining their excellent flame retardant properties. In general, the toughness of foams can be improved by two methods: the physical method and the chemical

Reinforcing urea‐formaldehyde based composite foam by formation of tailored chemical/mechanical interlocking structure

“…A series of polyvinyl alcohol (PVA) modified UF foams were prepared by Yunwen Shen et al [15] The compressive strength of the foam with 1 wt% PVA reached 215 KPa, which was much higher than that of neat foam (50 KPa). Zixuan Wang et al [16] introduced nano-zinc oxide (ZnO) into phenolurea-formaldehyde (PF/UF) foam, and found that the bending strength and compression strength of PF/UF/ZnO nanocomposite foam could reach 0.28 and 2.63 MPa, which increased by approximately 47.4% and 200% compared with PF/UF foam. In our previous study, [17,18] aramid fiber (AF) was introduced into UF foam via in situ preparation.…”