# A Review of the Synthesis and Applications of Polymer-Nanoclay Composites
## 2 Synthesis
### Melt-Blending Method  
The melt-blending method blends the desired amount of intercalated nanoclay particles with polymers at a temperature above the polymers' softening point in the presence of an inert gas [72; 73; 74; 75] (Figure 3). The melt-blending method provides better mixing of the polymer and nanoclay fillers compared to the solution-blending method and is compatible with current industrial processes such as \begin{table}
\begin{tabular}{c c c} \hline
**Nanoclay** & **Polymer** & **Reference** \\ \hline Co-Al-LDH & PS & [67] \\ Cloisite® 30B & Chitosan/polylactide & [68] \\ Mg-Al-LDH & Epoxy & [69] \\ Mg-Al-LDH & Acrylic resin & [70] \\ Cloisite and sepiolite & Hydrogenated nitrile butadiene rubber & [71] \\ \hline \end{tabular}
\end{table} 
Table 2: Polymer/nanoclay composite made by solution blending. All these composites have an intercalated clay structure. PS: polystyrene. Figure 2: Solution-blending method scheme. extrusion and injection molding, particularly for thermoplastic and elastomeric material fabrication [33]. The absence of solvents reduces the environmental impact and minimizes potential interactions between the host and polymer solvents, which, in many cases, limits clay dispersion [76]. The melting conditions, such as feed rate, temperature profile, rotor/screw speed, mixing time, oxidative environment, die pressure, material grades and contents, as well as the chemical nature of the nanoclay filler and polymers, are important parameters for the synthesis of the composites [77]. An enthalpic driving force for the functionalized macromolecules, a relatively large interlayer spacing for the macromolecular Gaussian coil, and sufficient time for the diffusion process of the center-stacked layers are three essential elements in the melt-blending method [78]. The melt-blending process can either be static or dynamic. In static melt blending (melt annealing), the process is carried out under a vacuum at temperatures of approximately 50 \({}^{\circ}\)C above transition temperatures in the absence of mixing [79]. In dynamic melt blending, the melting is performed in a melt mixer in the presence of an inert gas [80]. Melt mixers are categorized as batch (internal) and continuous (extruder) mixers [81]. A practical mixer provides excellent control over residence time, shear, temperature, and pressure, which are important while compounding heat-sensitive materials or dispersing nanoclay fillers [56]. The common batch mixers are the laboratory type manufactured by Brabender or Haake and their homologues on the large scale are manufactured by Banbury or Moriyama as dispersion mixers. Significant heat conduction by the mixing shafts is an important drawback of these mixers [56]. Recently, several melt mixers were designed to develop novel melt blending processes for advanced thermoplastic and elastomeric polymer/nanoclay composites (Table 3) [82]. [PERSON] et al. [83] applied a disk-screw extruder to prepare an organo-bentonite with polyamide, PS and polypropylene (PP) using the melt-blending method. The result showed that organo-MMT layers are well exfoliated and dispersed into the polymer matrix. Poly(methyl methacrylate) (PMMA) composites with an intercalated structure were successfully fabricated by [PERSON] et al. [84] using melt blending with a functionalized pristine sodium MMT and organically-modified Cloisite(r) 20A (BYK Additives & Instrument, Wesel, Germany). The composite exhibited superior thermal stability and tensile strength compared to neat PMMA and PMMA/pristine sodium MMT composites. [PERSON] et al. [85] used two polyamides (PA 6 and PA 12) to prepare PP/polyamide nanoclay composites by simultaneously melt blending two polyamides and MMT nanoparticles. The MMT clay nanoparticles appeared to be mostly located at the interface and formed a composite interphase. [PERSON] et al. [86] developed a biodegradable polymer/nanoclay composite using a novel natureplast PBE 003/poly(butylidene adipate-co-terephthalate) with various expanded organoclays by melt blending.