Non‐Ionic, Poly(ethylene oxide)‐Based Surfactants as Intercalants/Dispersants/Exfoliants for Poly(propylene)‐Clay Nanocomposites

Abstract

Summary: Poly(propylene) (PP)‐clay nanocomposites were prepared from unmodified montmorillonite clays (NaMMT), with poly(ethylene oxide)‐based nonionic surfactants as dispersants/intercalants/exfoliants. The primary objective of this research was to find dispersants that (a) allow PP nanocomposites to be formed by direct melt mixing; (b) are effective with unmodified clays and (c) comprise of only a minor component with respect to both the clay and the overall composition. Linear, branched, gemini and sugar‐based surfactants and structures containing poly(dimethyl siloxane) and poly(methyl methacrylate) blocks were examined. These additives were found to be effective in breaking down the clay agglomerates to tactoids, giving some expansion of the clay structure and partial exfoliation and providing substantially improved clay dispersion. The properties of the derived nanocomposites depend on the level of additive and its structure. Tensile and impact properties show significant improvement over the precursor PP. Also notable are the significantly better thermal and thermo‐oxidative stabilities, as compared to both PP and “clay alone” composites. For optimal properties, it is both necessary and desirable that the surfactant should only be a minor constituent (20–50%) of the composition, with respect to the clay. A preferred surfactant is linear PE‐block‐PEO, with a short PEO block and an alkyl chain with approximately 30 carbon atoms (C30). magnified image

New Composite Materials in the Technology for Drinking Water Purification from Ionic and Colloidal Pollutants

“…An alternative way to produce thermally stable nano-composites is the use of unmodified clays in combination with selected copolymers playing role of dispersants, intercalants, exfoliants and compatibilisers for PP nano-composites. In current processing of nano-composites different structures are identified such as polyethyleneoxide based nonionic surfactants [22] and amphiphilic copolymers based on long-chain acrylates [23]. Recently, more specifically poly(octadecylacrylate-co-maleic anhydride) and poly(octadecylacrylate-co-N-vinylpyrrolidone) in the form of gradient copolymers are applied with unmodified montmorillonite for processing PP nano-composites.…”

Oxygen barrier property of polypropylene-polyether treated clay nanocomposite

“…The silicate layers of the clay are 'incompatible' with organic polymers, due to surface hydroxyl groups; the smectite clays are usually treated to make them hydrophobic by ionexchange of the sodium interlayer cations with long-chain alkyammonium cations [2,15]. Instability of ammonium salts at temperatures encountered in melt mixing greater than 200°C leads to discolouration of the polymer matrix [2,16,17]. Hoffmann elimination can occur under basic conditions; for instance in the presence of sodium hydroxide, quaternary ammonium salts decompose by Hoffmann elimination, yielding the corresponding trialkyl amine and an alkene [16][17][18]26] (Figure 1).…”

“…Instability of ammonium salts at temperatures encountered in melt mixing greater than 200°C leads to discolouration of the polymer matrix [2,16,17]. Hoffmann elimination can occur under basic conditions; for instance in the presence of sodium hydroxide, quaternary ammonium salts decompose by Hoffmann elimination, yielding the corresponding trialkyl amine and an alkene [16][17][18]26] (Figure 1). Crown ethers and cryptands are more expensive than all other intercalants; however they are stable under higher temperatures up to 200°C [19].…”

“…WAXS is one the methods for characterising the state of intercalation and exfoliation of clay gallery layers [2,10,16]. X-ray data on the treated clay composites was collected on a Bruker AXS D8 Advance wide-angle X-ray diffraction instrument at 45 kV and 30 mA.…”

Efficient one-step melt-compounding of copolyetheramide/pristine clay nanocomposites using water-injection as intercalating/exfoliating aid

“…Even though the exact mechanism is still in debate, it is clear that there are driving forces for polyethers to enter layered pristine silicates galleries. Indeed, various polyethers were used to successfully prepare nanocomposites filled with pristine montmorillonite (NaMMT) [35,36] and the efficiency of PEO as intercalant for the preparation of apolar polymers/ NaMMT has been demonstrated [37,38]. Because of the above mentioned affinities for montmorillonite offered by polyethers and polyamides, trials have been successfully undertaken to prepare polyether-block-amide (PEBA)/clay nanocomposites, varying polyamide and polyether blocks [39][40][41].…”