Flame Retardant Coatings on Cotton Textiles: Polyelectrolyte-Nanoclay Assemblies

摘要

Layer-by-layer (LbL) assembly has become a popular method to fabricate multifunctional films that are typically less than one micrometer thick. A variety of LbL-assembled functional thin films are currently being evaluated for properties that include antimicrobial, antireflection, electrochromic, sensing, oxygen barrier-10 and biomedical applications. Films are created by alternately exposing a substrate to positively- and negatively-charged molecules or particles, as shown in Figure 1. In this case, steps 1 – 4 are continuously repeated until the desired number of "bilayers" (or cationic-anionic pairs) is achieved. Previous work has shown that a synthetic clay, Laponite, can impart flame-retardance to cotton fabrics via LbL assembly. In the present report, montmorillonite (MMT) was used as a component of an LbL assembly, with branched polyethylenimine ( B P E I ) a s t h e p o l y m e r c o u n t e r p a r t . T h i s L b L p r o c e s s i s environmentally friendly, carried out under ambient conditions and using only water-based solutions. The thickness and weight composition of these films can be modulated by changing the pH of the polymer solution and the concentration of the clay mixture. Four different polymer/clay formulations were applied onto the cotton fabrics. The flame-retardant properties were studied by thermogravimetric analysis (TGA) and vertical flame test.