Montmorillonite Modification And Polystyrene/montmorillonite Nanocomposites' Synthesis And Characterization

Compared with virgin polymer or conventional micro- and macro-composites, polymer-layered silicate nanocomposites(PLSN) materials have high moduli, superior mechanical and thermal properties, decreased gas permeability and flammability, increased biodegradability of biodegradable polymers and heat distortion temperatures. So it has continuously attracted intensive and extensive interests since Toyota researchers first published their work on nylon 6-clay hybrid materials in the late 80s and early 90s.An effective approach for preparing polymer layered silicate nanocomposites (PLSN) is in-situ polymerizations. To ensure good compatibility between polymer and inorganic phase (silicate) some modification is necessary in the process of preparing PLSN.To preparing PLSN, montmorillonite has been used in common which belongs to smectite group of clay minerals, which has a 2:1 type of layer structure. It is comprised of negatively charged silica sheets held together by charge-balancing counterions such as Mg²⁺, Na⁺, and Ca²⁺. Besides the interlayer cations, the interlayer space of smectite group of clay minerals contains large amounts of water molecules. As a result, various organic cations can be inserted into the interlayer galleries by an ion exchange process, forming an inorganic clay-organic montmorillonite. The formation of the so-called nano-composite can be accomplished easier, if the galleries become hydrophobic. This is usually done by cationic exchange, using alkyl-ammonium salts.By optimizing modified reaction conditions (reaction time, temperature, reaction medium etc), CPC-MMT and SDS-MMT are prepared from natural MMT by cation exchange with the anion surfacetants sodium laurylsulfonate (SDS) and cation surfacetants cetylpyridinium chloride (CPC). Under the optimized conditions, using different surfacetants such as organic cations, organic anions and inorganic cations inserted MMT, prepared first modified MMT and second inserted MMT. The modified MMT is characterized by FT-IR, XRD and TG, the results shows that the reagents have intercalated into the layers of MMT and some profitable conclusion was obtained. And the theory of organic anions inserted MMT was also put forward in the article.Polystyrene/MMT (PS/MMT) nanocomposites were prepared through suspension grafting polymerization and suspension polymerization by suspending the surfactant-treated MMT in styrene monomer. IR spectroscopic analysis confirmed the existence of the modified agent in the intercalated MMT samples. We used X-ray diffraction (XRD) to characterize the MMT structure. The properties of these PS/MMT nanocomposites were characterized by thermogravimetric analysis (TGA or TG). The results showed that nanocomposites had a special structure in which montmorillonite is dispersed homogeneously in polystyrene in nanoscale leading to better properties than original polymers. At last, the nanocomposites was prepared from local resource, MMT produced form PingLiang of GanSu province.