Chapter 19 - Self-extinguishing Polymer Blends Containing Organoclays

Abstract

We have shown that ditallow functionalized clays can be replaced almost completely by phosphorus-based flame retardant, resorcinol bis(diphenyl phosphate) (RDP) coated clays in enhancing the mechanical, thermal, gas barrier, and flame retardant (FR) properties of polymers and polymer blends. In selected cases, such as styrenic and polyolefin polymers, these clays may even perform better, and achieve a higher degree of exfoliation. A major advantage of the RDP-coated clays is the ease with which they could be produced simply by adsorption and mechanical agitation, without the use of potentially toxic solvents or reagents. The properties of Langmuir–Blodgett (LB) films of the RDP clays lifted onto Si substrates were studied using X-ray reflectivity, scanning force microscopy, and contact angle goniometry, showing that RDP coated the clay surfaces and intercalated into the galleries forming a layer of molecules approximately 2.2nm thick. AFM contact angle goniometry of bilayer polymer/clay LB films annealed on the RDP clay LB films was also performed. This technique was shown to be a rapid screen for the interfacial energy between functionalized clays and polymers, which could be used to predict exfoliation. TEM performed on RDP or ditallow-coated clay/polymer nanocomposites confirmed the technique which predicted segregation of the RDP clays to PS/PMMA, PC/SAN, and PLA/Ecoflex blend interfaces, achieving and a high degree of compatiblization. We also showed that the interfacial energy between polymers influences their FR properties such as time to ignition as well as heat and mass loss rates. Finally, we showed that RDP-coated clays were not cytotoxic and hence they should not raise concerns when used as components of biodegradable polymers.