Thermally stable organoclay

Thermal stability of polystyrene nanocomposites from improved thermally stable organoclays... 

Polystyrene/clay nanocomposites from thermally stable organoclays 71... 

Fully exfoliated PS/clay nanocomposites were prepared via free radical polymerization in dispersion [58, 59]. Thermally stable organoclay was obtained by modifying MMT with 3-(trimethoxysilyl)propyl methacrylate (MPTMS) (Table 3.4, Figure 3.14). Analyses by XRD and TEM revealed that nanocomposites with low clay loadings exhibited exfoliated structures, whereas intercalated structures were obtained at higher clay loadings. Another silane-type organoclay was prepared by modification of vermiculite with the... 

Two polymerizable cationic surfactants were synthesized to produce thermally stable organoclays (ll-acryloyloxyundecyl)dimethyl(2-hydroxyethyl)ammonium bromide (called hydroxyethyl surfmer), and (ll-acryloyloxyundecyl)dimethylethylammonium bromide (called ethyl surfmer (Table 3.5) [63]. PS nanocomposites were produced by bulk polymerization and by free radical polymerization using these organoclays. Exfoliated structures were obtained with the ethyl surfmer-modified clay, whereas a mixed exfoliated/ intercalated structure was obtained using the hydroxyethyl surfmer-modified clay. The nanocomposites exhibited enhanced thermal stability and an increase in the glass transition temperature, in addition to improved mechanical properties relative to polystyrene. However, intercalated structures were obtained when nanocomposites were prepared in solution, because of competition between the solvent molecules and monomer in penetrating the clay galleries. Enhanced thermal stability was also obtained in the solution polymerization case. 

Other thermally stable organoclays for atom transfer radical polymerization were considered DCTBAB and PCDBAB (Table 3.5) [64], Organoclays were used to prepare nanocomposites by polymerization of styrene in bulk. The thermal stability of the nanocomposites decreased as the clay loading increased, because of the competing effects of the number of attached chains relative to the unattached chains, level of clay exfoliation, and clay distribution. The overall thermal stability improved slightly. 

The development of a complete formulation and processing system for the production of nanocomposites or thermally stable clays and nanocomposites must resolve a number of important issues, beyond the thermal stability of the clay modifier. We will describe some aspects of the approach followed by our group to achieve this goal. The main objective of the case study to be described was to evaluate a number of phosphonium compounds for the production of thermally stable organoclays that would be suitable for preparing satisfactory PS nanocomposites by melt-compounding. 

When a thermally stable organoclay treated with alkyl phosphonium is used [15], there is no reason to reduce the mechanical properties since no amorphous styrenics are added. Instead, there would be increasing tendencies of... 

In this work, alkyl pyridinium, itnidazolium and phosphonium cationic surfactants were used to produce highly thermally stable organoclays. The volatile products issued from the thermal decomposition of those organoclays were analyzed by mass spectroscopy (MS). The organoelays were compounded with LLDPE and an appropriate compatibilizer. The micro- and nanodispersions were investigated through X-ray diffraction (XRD) and electron microscopy (SEM, TEM). The thermal stability of the nanocomposites was evaluated by thermogravimetric analysis (TGA). 

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