Polymerization melt intercalation

Several techniques such as intercalation of polymer from solution, in-situ intercalative polymerization, melt intercalation, direct mixture of polymer and particulates, template synthesis, in-situ polymerization and solgel process, are being employed for the preparation of polmer-layered silicate nanocomposites. Among them the most common and important approaches are in-situ polymerization, solution-induced intercalation method, and melt processing method, which are briefly discussed below. 

Several techniques may be used to produce polymer-MMT nanocomposites, including in-situ polymerization, melt intercalation, and solution casting however, to date in-situ polymerization has produced the best dispersed systems for PS-MMT nanocomposites [8]. This technique offers the advantage of allowing the monomer to penetrate the intergallery spaces first, which aids the exfoliation process. If the polymerization reaction can occur between the clay layers, the delamination process is further enhanced as growing polymer chains can push the clay layers apart, which is the main reason for the superior dispersed systems observed [8]. There are several in-situ polymerization techniques which may be used to form... 

The four main strategic processes for preparing polymer/layered silicate nanocomposites are exfoliation-adsorption, in situ intercalative polymerization, melt intercalation and template synthesis. ... 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

Nylon-6-clay nanocomposites were also prepared by melt intercalation process [49]. Mechanical and thermal testing revealed that the properties of Nylon-6-clay nanocomposites are superior to Nylon. The tensile strength, flexural strength, and notched Izod impact strength are similar for both melt intercalation and in sim polymerization methods. However, the heat distortion temperature is low (112°C) for melt intercalated Nylon-6-nanocomposite, compared to 152°C for nanocomposite prepared via in situ polymerization [33]. 

Besides melt intercalation, described above, in situ intercalative polymerization of E-caprolactone (e-CL) has also been used [231] to prepare polycaprolactone (PCL)-based nanocomposites. The in situ intercalative polymerization, or monomer exfoliation, method was pioneered by Toyota Motor Company to create nylon-6/clay nanocomposites. The method involves in-reactor processing of e-CL and MMT, which has been ion-exchanged with the hydrochloride salt of aminolauric acid (12-aminodecanoic acid). Nanocomposite materials from polymers such as polystyrene, polyacrylates or methacrylates, styrene-butadiene rubber, polyester, polyurethane, and epoxy are amenable to the monomer approach. 

The manufacturing methods for PLA nanocomposites include intercalation of polymer from solution, polymer melt intercalation and intercalation of a suitable monomer and subsequent in situ polymerization. 

Polypropylene (PP) is one of the most widely used plastics in large volume. To overcome the disadvantages of PP, such as low toughness and low service temperature, researchers have tried to improve the properties with the addition of nanoparticles that contains p>olar functional groups. An alkylammonium surfactant has been adequate to modify the clay surfaces and promote the formation of nanocomposite structure. Until now, two major methods, i.e., in-situ polymerization( Ma et al., 2001 Pirmavaia, 2000) and melt intercalation ( Manias et al.,2001) have been the techniques to prepare clay/PP nanocomposites. In the former method, the clay is used as a catalyst carrier, propylene monomer intercalates into the interlayer space of the clay and then polymerizes there. The macromolecule chains exfoliate the silicate layers and make them disperse in the polymer matrix evenly. In melt intercalation, PP and organoclay are compounded in the molten state to form nanocomposites. 

Funck, A. Kaminsky, W. (2007) Polypropylene carbon nanotube composites by in situ polymerization. Compos. Sci. Technol. Vol.67, No.5, pp.906-915 Garda-Leiner, M Lesser, A. (2003) Melt Intercalation in Polymer-Clay Nanocomposites Promoted by Supercritical Carbon Dioxide. Polym. Mater. Sci. Eng. VoL89, pp.649-650... 

The ranges in which the clay platelets were present in the in-situ polymerized and melt-blended nanocomposite samples are given in Table 9.5. The average length of clay platelets seems to be approximately 65 nm for in-situ polymerized nanocomposites, whereas it is 100 nm for the nanocomposites prepared by melt intercalation technique. 

In the melt mixing method, nanoclays are incorporated into the polymer in the molten state. This technique has considerable advantages over either the in situ intercalative polymerization or polymer solution intercalation techniques. Firstly, this method is environmentally benign due to the absence of organic solvents. Secondly, melt processing is compatible with current industrial processes, such as extrusion and injection moulding. The melt intercalation method allows the use of biopolymers that were not suitable for in situ polymerization. This has been the most widely used method in the literature for obtaining PLA/clay nanocomposites. " ... 

It was the pioneering work of Toyota researchers toward the development of polymeric nanocomposites in the early 90s [1, 2], in which electrostahcally held 1-nm-thick layers of the layered aluminosilicates were dispersed in the polyamide matrix on a nanometer level, which led to an exponenhal growth in the research in these layered silicate nanocomposites. These nanocomposites were based on the in-situ synthesis approach in which monomer or monomer solution was used to swell the filler interlayers followed by polymerizahon. Subsequently, GianneUs and CO workers [3, 4] also reported the route of melt intercalation for the synthesis of polymer nanocomposites. 

From an industrial point of view, the melt-intercalation technique is usually preferred to in-situ polymerization because it is simpler and uses already existing technologies. In this sense, methods that combine the efficiency of the in-situ... 

Several methods have been used to obtain polymer nanocomposites by using organoclays [29-32], i.e. solution intercalation [33-39], melt intercalation [40, 41], and in situ interlayer intercalation [30, 42, 43], Among them, in situ interlayer polymerization relies on swelling of... 

A number of methods have frequently been employed in the production of nanocomposite materials. These include solution intercalation, melt intercalation, polymerization, sol-gel, deposition, magnetron sput-tering, laser, ultrasonication, supercritical fluid, etc. In PHA nanocomposite fabrication, solution intercalation and melt intercalation methods are the most widely explored procedures. However, use of in situ intercalative polymerization, supercritical fluids and electrospinning are shown to be promising and emerging techniques. The performance and quality of a nanocomposite depends on how well the nanofillers disperse or blend into the matrix. Therefore, these methods constitute different strategies to improve the composites thermo-mechanical and physico-chemical properties by enhancing efficient interactions between the nanofiller and the polymer matrices. 

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