Teaching TopicChapter 6 Polymer nanocomposites Lecturing hours 180 minTeaching Objectives1. Know the general features of polymer nanocomposites; 2. Know the preparation methods of polymer nanocomposites; 3. Know the characterization of polymer nanocomposites.Teaching Emphases1. The feature of polymer nanocomposite. 2. The preparation of polymer nanocomposite.Teaching Difficult PointsThe characterization of nanocomposites.Teaching MethodsLecturing + PPT + discussion + interactionTime Arrangement Teaching content45 min6.1 Introduction 1. definition When inorganic phases in organic/inorganic composites become nanosized, they are called nanocomposites. Organic/inorganic nanocomposites are generally organic polymer composites with inorganic nanoscale building blocks. 2. Advantages inorganic material organic polymer 3. Defining feature of polymer nanocomposites the small size of the fillers leads to a dramatic increase in interfacial area as compared with traditional composites. This interfacial area creates a significant volume fraction of interfacial polymer with properties different from the bulk polymer even at low loadings. 4. Inorganic nanoscale building blocks Nanotubes; Layered silicates (montmorillonite, saponite), Nanoparticles of metals (Au, Ag), Metal oxides (TiO2, Al2O3), Semiconductors (PbS, CdS), Others. 5. Polymer/Silica SiO2 is viewed as being very important. Polymer/silica composites are the most commonly reported in the literature. They have been employed in a variety of applications. 6. Discuss: what is nanocomposite?6.2 Preparation of nanocomposite Organic or inorganic polymerization generally becomes necessary if at least one of the starting moieties is a precursor. Blending is generally just mixing of the silica nanoparticles into the polymer; a sol-gel process can be done in situ in the presence of a preformed organic polymer or simultaneously during the polymerization of the monomer(s); the method of in situ polymerization involves the dispersion of nanosilica in the monomer(s) first and then polymerization is carried out 45 min6.2.1 Blending 6.2.1.1 Melt blending Melt blending is most commonly used because of its efficiency, operability, and environmental containment. Matrices: Polymers and polymer blends Level : less than 3 vol % many advantages: being simple, low cost, easy to control and broadly applicable. 6.2.1.2. Solution Blending Solution blending is a liquid-state powder processing method that brings about a good molecular level of mixing and is widely used in material preparation and processing. Some of the limitations of melt mixing can be overcome if both the polymer and the nanoparticles are dissolved or dispersed in solution but at a cost depending on the solvent and its recovery. The location for solution blending is not limited to a solution can include a latex or a suspension. and then compression molding is also applied. 6.2.1.3 Other Blending Methods To overcome these problems is : to process the polymer in the solid state, which avoids the thermal and solvent problems encountered with traditional technologies while providing almost infinite design flexibility and processing simplicity. 6.2. 2 Sol-Gel Process Sol-gel reaction is a method to prepare ceramic precursors and inorganic glasses at relatively low temperatures. The major advantage of the process is that mild conditions, such as relatively low temperature and pressure, are used in this type of processing of ceramics. the sol-gel process can be viewed as a two-step network forming process: the first step being the hydrolysis of a metal alkoxide the second consisting of a polycondensation reaction. The properties of the resulting nanocomposites influenced by particle sizes and interaction between the dispersed and continuous phases. According to the nature of interfacial interaction, hybrid materials can be divided into two distinct classes, 6.2.3 In Situ Polymerization 6.2.3.1. General Polymerization There are several advantages of using the in situ polymerization method. These include: ease of handling, the speed of the process, and better performance of the final products. The process of in situ polymerization involves three continuous steps: The most important factors that affect the properties of composites are: the dispersion and the adhesion at the polymer and filler interfaces. Inorganic particles may disperse homogeneously in the polymer matrices when they are premodified by a coupling agent. 6.2.3.2 Photopolymerization It is a process where UV light induces the polymer formation allowing a fast transformation of the liquid monomer into the solid film with tailored physicochemical and mechanical properties. In the process, radical or cationic species are generated by the interaction of the UV light with a suitable photoinitiator, which induce the curing reaction of reac