Self-extinguishable Non-toxic Layer-by- Layer Coating on Flexible Polyurethane Foam

摘要

Layer-by-layer (LbL) assembly is a popular method to fabricate multifunctional films that are typically less than one micrometer thick1-3 A variety of LbL-assembled functional thin films are evaluated for properties that include antimicrobial, sensing, anti-reflection, electrochromic, oxygen barrier and biomedical applications. Films are created by alternately exposing a substrate to positively- and negatively-charged molecules or particles, as shown in Figure 1(a). Steps 1 - 4 are continuously repeated until the desired number of "bilayers" (or cationic-anionic pairs) is achieved. Recently, flame retardant properties were successfully imparted via LbL assembly on cotton fabric with sodium montmorillonite clay, and intumescent coating. In this study, two coating systems were applied on polyurethane foam (PUF), branched polyethylenimine- montmorillonite/poly (acrylic acid) (BPEI/MMT/PAA) trilayer (TL) system (Fig. 1(b)), and poly (allylamine)/poly (sodium phosphate) (PAAm-PSP) bilayer (BL) system. PAA in TL system can seal the MMT layer and achieve a more uniform negatively-charged surface coverage. Two coating systems were also combined and applied onto PUF (Fig 1(c) and (d)), in order to prevent the melt-dripping problem of PUF once it was ignited, and to delay the burning process resulted from the intumescent phenomenon. This LbL process is environmentally friendly, carried out under ambient conditions and uses only water-based solutions.