Role of Surface Interactions in the Synergizing Polymer/Clay Flame Retardant Properties

Abstract

The absorption of resorcinol di(phenyl phosphate) (RDP) oligomers on clay surfaces has been studied in detail and is being proposed as an alternative method for producing functionalized clays for nanocomposite polymers. The ability of these clays to be exfoliated or intercalated in different homopolymers was investigated using both transmission electron microscopy and small-angle X-ray scattering results, compared with contact angle measurements on Langmuir-Blodgett clay monolayers, where the interfacial energies were used as predictors of the polymer/clay interactions. We found that the contact angle between PS/RDP clay monolayer substrates was ∼2.5°, whereas the angle for polystyrene (PS)/Cloisite 20A clays substrates was ∼32°, consistent with the large degree of exfoliation observed in PS for the RDP-coated clays. The interfacial activity of these clays was also measured, and we found that the RDP-coated clays segregated to the interfaces of PC/poly(styrene-co-acrylonitrile) blends, while they segregated into the poly(methyl methacrylate) (PMMA) domain of PS/PMMA blends. This morphology was explained in terms of the relative energy advantage in placing the RDP versus the Cloisite clays at the interfaces. Finally, we demonstrated the effects of the relative surface energies of the clays in segregating to the blend air interface when heated to high temperatures. The segregation was shown to affect the composition and mechanical properties of the resulting chars, which in turn could determine their flame retardant response.

Phase behavior of UCST blends: Effects of pristine nanoclay as an effective or ineffective compatibilizer

“…It has been found that the addition of solid nanoparticles with at least one dimension in the nanometer scale can affect the compatibility of components and improve the physical, mechanical and thermal properties of the blends [2][3][4][5]. The improved miscibility of polymer mixtures in the presence of nanofillers has been reported by different groups with reduced dispersed phase domains, narrower droplet size distribution in matrix-dispersed morphology, enhanced ductility and mechanical properties, lower interfacial tension between two phases and more morphological stability in the subsequent melt blending processes [5][6][7][8][9][10]. As shown theoretically by Nesterov and Lipatov [11][12], the compatibilization effect of solid filler (F) on an immiscible polymer pair (A and B) can be described by the mixing free energy of system (!G mix ) which consists of the absorption free energy of each polymer on the solid surface of F (!G AF and !G BF ) and the interaction …”

Recent Advances on Montmorillonite-Based Fire Retardant Composites in Polymer Matrices

“…However, phosphonium surfactants are more thermally stable compared to the ammonium salts and can be used [58]. Pack et al employed resorcinol diphenylphosphate (RDP) oligomers as a surfactant to modify pristine MMT [43]. RDP is a phosphorus-based fire retardant with good thermal stability, high efficiency, and low volatility [37].…”

The influence of multiple modified MMT on the thermal and fire behavior of poly (lactic acid) nanocomposites

“…Meanwhile, the oligomers also have the phosphoryl groups that act as a strong hydrogen bond acceptors and, together with the phosphorus groups which comprise 10.7 wt%, are known to react with polymer residues at high temperatures forming stable chars. [23] Consequently, RDP are usually used in polymer as flame retardants. Moreover, it is also a biodegradable compound with high thermal stability and excellent compatibility with the polymer matrix.…”