Polymer Materials and their Processing

Polymers are formed by the repeat units of monomers by addition or condensation reactions. They are long-chain molecules, which comprise main monomer unit repeats throughout the structure. Hundreds and even thousands of repeated monomers form one polymer chain. 

Polymers differ from other materials by the size of their molecules. They consist of thousand or tens of thousands of atoms. They also have a macroscopic rectilinear length. The atoms of macromolecules are firmly held together by valence bonds, forming a single entity. The weaker van der Waals forces have an effect on the components of the macromolecules. The structure of polymer is more complicated. 

Polymers are viscoelastic in nature. They have interesting rheological properties, which exhibit elasticity and viscous flow [1]. During the application of stress, the polymeric material undergoes a strain, which is dependent upon the applied stress. Removal of stress on the material may not return to its original dimensions, which has certain permanent 

In the manufacturing flnished products, polymeric materials are useful for a variety of end use, which includes many light engineering applications. Advantages of polymers over metals can be quickly summarized as follows [2]  

Polyethylene (PE) is globally produced and consumed as commodity polymer. It has high-impact strength, low brittleness temperature, flexibility, and outstanding electrical properties. It is partially crystalline, with increase in molecular weight, and it provides better tensile and environmental stress-cracking resistance [3]. 

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This document provides definitions of the terms most commonly used in relation to sol-gel processing and ceramization. It embraces all categories of materials and their processing. The definitions result from the efforts of a working party drawn from the membership of the lUPAC Polymer and Inorganic Chemistry Divisions. 

This section introduces a novel application of IR spectroscopy, namely IR imaging, and the specific sampling technique of attenuated total reflectance (ATR). FTIR imaging in ATR mode allows one to visualize the spatial distribution of different components in polymeric materials and to study directly the effect of high-pressure CO2 on this distribution. This novel approach should benefit polymer scientists studying polymer blends and their processing with SCCO2. 

AVhile the Series is primarily classified on the basis of types of materials and their processing modes, some volumes will focus on particular groups of applications (Nuclear Materials, Biomedical Materials), and others on specific categories of properties (Phase Transformations, Characterization, Plastic Deformation and Fracture). Different aspects of the same topic are often treated in two or more volumes, and certain topics are treated in connection with a particular material (e.g., corrosion in one of the chapters on steel, and adhesion in one of the polymer volumes). Note, however, that corrosion is now to receive its own dedicated volume, number 19. Special care has been taken by the Editors to ensure extensive cross-references both within and between volumes, insofar as is feasible. A Cumulative Index volume will be published upon completion of the Series to enhance its usefulness as a whole. 

The crystallization of homopolymers yields a hierarchical structure in polymer materials, which substantially controls their physical properties. Therefore, the crystalline morphology of homopolymers has been one of the important research subjects in polymer science. In addition, the crystallization of homopolymers spatially confined in various nanodomains, such as micelles, AAO, or microdomain structures, may bring new information on crystallization mechanisms of homopolymers, because it will be possible to highlight a specific crystallization mechanism (e.g., nucleation or crystal growth) in the overall crystallization process consisting of several combined mechanisms. Furthermore, the crystallization in nanodomains has the possibility of providing new polymer materials, and their physical properties should be unique as compared with usual polymer materials. This is because the substantial control of nano-ordered structures formed in polymer materials will be possible by this crystallization, which is never achieved by the crystallization of neat homopolymers. 

In the discussion of these combined topics, we use statistics extensively because the description of microstructure requires this kind of approach. This is the basis for merging a discussion of copolymers and stereoregular polymers into a single chapter. In other respects these two classes of materials and the processes which produce them are very different and their description leads us into some rather diverse areas. 

Vinyl chloride has been known for over a hundred years and its polymerization to polyvinyl chloride (PVC) was achieved in 1912. Industrial-scale production of this plastic began in 1927. PVC is still the most versatile plastic. One of the reasons for this is the numerous variations made possible by the method of manufacture of the polymer, namely by copolymerization with other monomers and their processing. Thus, PVC can be thermoformed on all conventional processing machines if the slight thermal damage is taken into consideration. Machining is easy and the material can be bonded, bent, welded, printed and thermoformed. 

High-pressure processes have been widely applied in the polymer industry. Near-critical and supercritical fluids (SCFs) are in particular used owing to their easily tunable density, which enhances the control of polymer solubility and their good separability from polymer material [1], SCF solvents (e.g. scC02) offer a potential advantage for separation process. The solubility of different polymeric material in SCFs can be systematically varied by changing operating conditions. Several... 

X HE USE OF CHEMICAL APPROACHES to improve the processing, properties, and performance of advanced ceramic materials is a rapidly growing area of research and development. One approach involves the preparation of organometallic polymer precursors and their controlled pyrolysis to ceramic materials. This chapter will review the preparation and application of silicon-, carbon-, and nitrogen-containing polymer systems. However, the discussion is not exhaustive the focus is on systems with historical significance or that demonstrate key technological advances. 

Photoconductivity is based on the conversion of light to electricity. The reverse phenomenon, electroluminescence, is based on the conversion of electricity to light. Electroluminescence is useful for flat-panel display and 11-VI semiconductors such as ZnS are employed for this purpose [132], The current trend is toward the development of polymeric electroluminescent material for their processing flexibility [133,134]. It has already been demonstrated that properly doped semiconductor nanoclusters such as ZnIMn1 IS emits light efficiently [135], With the demonstration of photoconductivity [101 103] these nanocluster-doped polymers can become interesting candidates of electroluminescent materials. No experimental work has been performed yet. 

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