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

Abstract

AbstractUrea‐formaldehyde (UF) foam is considered to be a potential alternative for commercial polymeric foams due to its intrinsic flame retardancy and inexpensiveness, but it showed high brittleness and low strength, which restricts its wide applications. In this work, glass fiber powder (GF) was selected as the reinforcing filler, and by formation of tailored chemical/mechanical interlocking structure for the composite system, UF foam was highly reinforced. The surface of GF was coated with granular polydopamine (PDA) layer through self‐polymerization of dopamine, and then, carbon nanotubes (CNTs) were further grafted onto GF surface with high grafting ratio via the bridge effect of PDA to construct a network like entanglement structure. The active groups of PDA layer on GF surface generated chemical/hydrogen bonding interactions with UF matrix, while rough CNTs network structure promoted the mechanical interlocking between GF and UF resin. Such multiple interfacial enhancement improved the stress transmission ability of the interface, exhibiting “supporting” on the cell wall and “cracks bridging” effect of GF. Compared with neat UF foam, the composite foam exhibited smaller cell size, narrower cell size distribution, higher cell density, more complete closed cell structure, while compressive strength and modulus of the composite foam increased by 78.7% and 90.08%, respectively. Moreover, the composite foam showed improved thermal stability and excellent flame retardancy with V‐0 rating of UL‐94 tests.