5. In Situ Polymerization 3907 5.1. General Polymerization 3907 5.2. Photopolymerization 3910 5.3. Surface-Initiated Polymerization 3912 5.4. Other Methods 3913 6. Colloidal Nanocomposites 3913 6.1. Sol-Gel Process 3914 6.2. In Situ Polymerization 3916 6.2.1. Emulsion Polymerization 3917 6.2.2. Emulsifier-Free Emulsion Polymerization 3919 6.2.3. Miniemulsion Polymerization 3920 6.2.4. Dispersion Polymerization 3921 6.2.5. Other Polymerization Methods 3923 6.2.6. Conducting Nanocomposites 3924 6.3. Self Assembly 3926 7. Other Preparative Methods 3926 8. Characterization and Properties 3928 8.1. Chemical Structure 3928 8.2. Microstructure and Morphology 3929 8.3. Mechanical Properties 3933 8.3.1. Tensile, Impact, and Flexural Properties 3933 8.3.2. Hardness 3936 8.3.3. Fracture Toughness 3937 8.3.4. Friction and Wear Properties 3937 8.4. Thermal Properties 3938 8.5. Flame-Retardant Properties 3941 8.6. Optical Properties 3942 8.7. Gas Transport Properties 3943 8.8. Rheological Properties 3945 8.9. Electrical Properties 3945 8.10. Other Characterization Techniques 3946 9. Applications 3947 9.1. Coatings 3947 9.2. Proton Exchange Membranes 3948 9.3. Pervaporation Membranes 3948 9.4. Encapsulation of Organic Light-Emitting Devices 3948

Polymer/Silica Nanocomposites: Preparation, Characterization, Properties, and Applications

Sol-gel based materials for biomedical applications

The recent introduction of nanoclays as fillers or additives in polymers for various desired effects is a subject of an increased interest for research and development to establish various applications. An increased consumption is indicated by the wider applications of clay nanocomposites approaching to almost one-quarter (24 pct) in 2005 of the total nanocomposites used. However, an interesting concern, along with the studies addressing how nanoclays change the behavior of polymeric materials, is to discover what are clays, nanoclays and montmorillonite minerals. The various structures of montmorillonite available in nature and their modification for application are discussed. An attempt is made to review the origin of using clays when nanotechnology did not exist, coupled with the effects of montmorillonite-based nanoclays on commercially known polymers.

Clays, Nanoclays, and Montmorillonite Minerals

The application of ammonium polyphosphate (APP) in different types of commodity thermoplastic composites (polyethylene, polypropylene (PP), polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET)) have been discussed in terms of mechanical properties, morphologies and thermal properties. In addition, engineering thermoplastics such as acrylonitrile-butadiene-styrene (ABS), polyamides and poly(vinyl alcohol) (PVOH) and their composites added with APP and other additives were analyzed as well. It was suggested that improvement of mechanical properties and morphologies of the thermoplastic composites could be made possible with appropriate amount of APP and other additives such as montmorillonite (MMT), pentaerythritol (PER) and different types of layered double hydroxide (LDH). Furthermore, thermal properties such as limiting oxygen index (LOI) values together with cone calorimetry and thermogravimetric analysis (TGA) performance could be enhanced through optimum combination of APP, PER and melamine which functions as intumescent flame retardant (IFR).

A review of application of ammonium polyphosphate as intumescent flame retardant in thermoplastic composites

Advanced silica/polymer composites: Materials and applications

Polymethylmethacrylate (PMMA)/silica nanocomposites are prepared by solution polymerization in this project and the resulting materials are subjected to characterization to evaluate thermal, mechanical, and fire properties. IR results show that both (3-acryloxypropyl)methydimethoxy-silane (APMDMOS) and (3-acryloxypropyl)trimethoxysilane (APTMOS) can serve as reagents for the surface modification of silica, while APTMOS performed better than APMDMOS for the modification of the silica surface. Mechanical properties of PMMA/silica nanocomposites prepared by solution blending showed decreased tensile strength and elongation at break, while materials from solution polymerization performed better than PMMA itself. Moreover, all prepared samples have shown improved thermal stabilities versus PMMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3844–3850, 2004

PMMA/silica nanocomposite studies: Synthesis and properties

Three polymer/silica nanocomposites were prepared by a single-screw extrusion approach: poly(methyl methacrylate), polystyrene and polycarbonate/silica nanocomposites. The resulting nanocomposites were subjected to comprehensive studies of mechanical, thermal and flammability properties. All materials showed improved mechanical performance and thermal stabilities, although they are not strictly flame retardant when subjected to fire tests like Oxygen Index or horizontal Bunsen burner tests. However, the nanocomposites showed reduction in peak heat release rates and total heat release when evaluated by cone calorimetry. Moreover, the polycarbonate showed improvement in flammability according to vertical burning tests. All polycarbonate materials subjected to vertical burning testing are V2 rated, but after flame times with 1% silica were significantly reduced. A flame retardant mechanism is proposed in order to understand the relationship between interfacial interaction and flammability of polymer/silica nanocomposites. Copyright © 2006 John Wiley & Sons, Ltd.

Polymer/silica nanocomposites prepared via extrusion

A comprehensive discussion on the flammability of organic-inorganic nano-composites is presented based on different fire testing methods. Based on various flammability tests, reduced peak heat release rate, an increased oxygen index, and an enhanced thermal stability were observed, while faster burning rates were found when the nanocomposites underwent horizontal and vertical burning tests. Moreover, it has also been found that when traditional flame-retardant additives were added to the nanocomposites, less additive was required to achieve the same level of flame retardancy.

Flammability of Polymer-Clay and Polymer-Silica Nanocomposites

Organic/inorganic nanocomposites and methods for their preparation are disclosed. In one embodiment, the method comprises the steps of providing an organic/inorganic concentrate and processing the concentrate with a polymer resin. In a preferred embodiment the organic/inorganic concentrate and polymer resin are processed by extrusion using a single-screw extruder. In another embodiment, the method further comprises surface modifying an inorganic additive, mixing the modified additive with a polymer solution to produce an organic/inorganic solution, and removing solvent from the organic/inorganic solution to produce the organic/inorganic concentrate. Processing of the organic/inorganic concentrate with a polymer resin produces a homogeneous nanocomposite with superior mechanical and thermal properties.

Organic/inorganic nanocomposites obtained by extrusion

Polymer nanocomposites (PNC) were prepared by a single-screw extrusion approach. Three polymers were investigated. They are polymethyl methacrylate (PMMA), polystyrene (PS), and polycarbonate (PC). The nanofillers employed in this research were fumed nanosilica and alumina. The resulting PNCs were subjected to a thermal stability study, UL94 evaluation and Cone calorimetry characterization, to demonstrate the chemical composition effects on the thermal degradation process and flammability of PNCs. The results show that silica as an “inert” filler enhanced the thermal stability of PNCs by radical trapping and chain mobility restriction effects. On the other hand, the “active” nanofiller alumina showed an additional heterogeneous catalyzing effect during the polymer decomposition process. The difference in decomposition mechanism for silica and alumina greatly affected a number of key physical parameters of polymer melts, which in turn changed the flammability of corresponding PNCs. Copyright © 2008 John Wiley & Sons, Ltd.

Impact of the chemical composition of nanofillers on the flammability of polymer nanocomposites

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