Technology & Engineering
Polymer Material
Polymer materials are large molecules composed of repeating structural units called monomers. They are versatile and can be found in a wide range of products, from plastics and rubber to fibers and adhesives. Their properties, such as flexibility, strength, and resistance to chemicals, make them valuable in various engineering applications.
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9 Key excerpts on "Polymer Material"
eBook - PDF- Anthony J Ryan(Author)
- 2007(Publication Date)
- Royal Society of Chemistry(Publisher)
It would also tend to have inferior mechanical properties, especially in the areas of toughness and chemical resistance. These are not insurmountable problems and once properly defined, it should be possible to make the Polymer Material with the correct balance of properties. The problem comes in the definition of the required design. Polymers are strongly influenced by their history - the manner of their synthesis, the thermal and mechanical forces they have been through all play a major role in controlling the distribution of the polymer chains relative to one another in space, and it is this state which largely determines the macroscopic properties of the polymer. The future of custom synthesis of designer polymers will therefore have to have a much higher input from the processing side of the technology. Although this is strong within the ‘materials’ end of the polymer spectrum, it is likely also to be true at the more specialist end. Consider as an example spider silk. It is spun out of water to form a water insoluble fibre - a transformation in properties brought about by moving from one kinetically stable state to another thermodynamically (??) stable one. As we design polymers to form micelles, or synthetic enzymes, we polymer scientists will have to understand and embrace the polymer technologists view of the world - perhaps a new discipline will be born - Polymer Engineers? 3 Sustainable Feedstocks This use of examples from nature and the need (stated in the first paragraph) for a smaller impact on the environment have led to a greater interest in Emerging Trends in Polymer Science 11 naturally derived building blocks for polymer structures. All the permutations on polymer structure and distribution of chemical functionality can be found in the polymeric systems used in nature - polysaccharides, polypeptides, lipids, etc.
eBook - PDFInorganic-Whisker-Reinforced Polymer Composites
Synthesis, Properties and Applications
- Qiuju Sun, Wu Li(Authors)
- 2015(Publication Date)
- CRC Press(Publisher)
1 Chapter 1 Introduction A substance that can meet specific morphological and physical performance requirements is referred to as a material. Materials are vital to modern industrial and high-tech advances, consti-tuting an important basis for human survival and development. Materials can be divided according to their chemical composi-tion into metallic, inorganic nonmetallic, and organic Polymer Materials. Metallic materials are composed of metal atoms such as iron, copper, aluminum, and alloy steel. Inorganic nonme-tallic materials are composed of inorganic compounds such as glass, ceramics, and cement. Organic Polymer Materials are composed mainly of two elements—carbon and hydrogen— with C–C covalent bonds forming their basic structure; exam-ples of such compounds include cottons, linens, silks, plastics, rubber, synthetic fibers, and others. As a rising star in the field of materials, Polymer Materials have widespread applications because of their unique features, such as availability of raw materials, low cost, low density, favor-able optical activity, diversity, high mechanical strength, chemi-cal resistance, and excellent insulation properties. Furthermore, Polymer Materials can also adapt to various needs, have good processibility, and are suitable for automatic production, and have therefore become an essential material in our everyday lives. 2 ◾ Inorganic-Whisker-Reinforced Polymer Composites In addition, with the development of the materials industry and improvements in technology, composite materials made from two or more constituent materials with different physi-cal or chemical properties that are combined with appropriate methods and provide the compound effects of the individual component have also become a large species in the materi-als field.
eBook - PDF- Saeed Farrokhpay(Author)
- 2023(Publication Date)
- Arcler Press(Publisher)
FUNDAMENTALS OF POLYMERIC MATERIALS 4 CONTENTS 4.1. Introduction ...................................................................................... 88 4.2. The History of the Concept of the Macromolecule ............................ 89 4.3. Classification of Polymers ................................................................. 91 4.4. Structure and Properties of Polymers ................................................. 93 4.5. Thermoplastic Polymers .................................................................... 93 4.6. Thermosetting Polymers .................................................................. 101 4.7. Naturally Occurring Polymers......................................................... 108 References ............................................................................................. 113 CHAPTER The Fundamentals of Materials Chemistry 88 4.1. INTRODUCTION A polymer is a big molecule comprised of a lot of smaller ones. Complex molecules can be strongly linked, mildly branching, or straight. The structure in the first example becomes a vast three-dimensional (3D) network (Morgan and Gilman, 2013; Dhote et al., 2019). Monomers are tiny molecules that serve as the fundamental foundations of larger compounds. The economically important substance poly(vinyl chloride), for example, is made from the monomer vinyl chloride. The polymer’s duplication component is usually the same as the monomer wherein the polymer was made. Although, there are several exceptions. Vinyl alcohol (CH 2 CHOH) recurring units are correctly considered to make up Poly(vinyl alcohol), yet there is no such monomer like vinyl alcohol. The relevant molecular unit is found in the alternate tautomeric for methanal (CH 3 CHO). The polymer poly(vinyl ethanoate) must first be made from the monomer vinyl ethanoate, and afterwards, the result must be hydrolyzed to create the polymer ethanol (Bloembergen, 1996; Roth and Baglay, 2016).
eBook - PDFPolymer Melt Processing
Foundations in Fluid Mechanics and Heat Transfer
- Morton M. Denn(Author)
- 2008(Publication Date)
- Cambridge University Press(Publisher)
1 Polymer Processing 1.1 Introduction Polymeric materials – often called plastics in popular usage – are ubiquitous in mod- ern life. Applications range from film to textile fibers to complex electronic inter- connects to structural units in automobiles and airplanes to orthopedic implants. Polymers are giant molecules, consisting of hundreds or thousands of connected monomers, or basic chemical units; a polyethylene molecule, for example, is simply a chain of covalently bonded carbon atoms, each carbon containing two hydrogen atoms to complete the four valence sites. The polyethylene used to manufacture plastic film typically has an average molecular weight (called the number-average molecular weight, denoted M n ) of about 29,000, or about 2,000 ---CH 2 --- units, each with a molecular weight of 14. The symbol “---” on each side of the CH 2 denotes a single covalent bond with the adjacent carbon atom. (The monomer is actually ethy- lene, CH 2 --- ---CH 2 , where “ --- ---” denotes a double bond between the carbons that opens during the polymerization process, and a single “mer” is ---CH 2 ---CH 2 ---; hence, the molecular weight of the monomer is 28 and the degree of polymerization is about 1,000.) The ultra-high molecular weight polyethylene used in artificial hips and other prosthetic devices has about 36,000 ---CH 2 --- units. Polystyrene is also a chain of covalently bonded carbon atoms, but one hydrogen on every second car- bon is replaced with a phenyl (benzene) ring. Two or more monomers might be polymerized together to form a copolymer, appearing on the chain in either a regu- lar or random sequence. The monomers for some common engineering plastics are shown in Table 1.1. The polymers used in commercial applications are solids at their use tempera- tures. The solid phase might be brittle or ductile, depending on the chemical com- position and, to some extent, on the way in which the polymer has been processed.
eBook - PDFFundamentals of Modern Manufacturing
Materials, Processes, and Systems
- Mikell P. Groover(Author)
- 2016(Publication Date)
- Wiley(Publisher)
The word is derived from the Greek words poly, meaning “many,” and meros (reduced to mer), meaning “part.” Most polymers are based on carbon and are therefore organic chemicals. As engineering materials, polymers are relatively new compared to metals and ceramics (see Historical Note 8.1 at www.wiley.com/college/groover). Polymers can be classified into three types: (1) thermoplastic polymers, (2) thermosetting polymers, and (3) elastomers. Thermoplastic polymers (TP), also called thermoplastics, are solid materials at room temperature, but they become viscous liquids when heated to temperatures of only a few hundred degrees. This characteristic allows them to be easily and economically shaped into products. They can be subjected to this heating and cooling cycle repeat- edly without significant degradation. Thermosetting polymers (TS), or thermosets, cannot tolerate repeated heating cycles as thermoplastics can; when initially heated, they soften and flow for mold- ing, but the elevated temperatures also produce a chemical reaction that hardens the material into an infusible solid. If reheated, thermosetting polymers degrade and char rather than soften. Elastomers (E) are polymers that exhibit extreme elastic extensibility when subjected to relatively low mechan- ical stress. Some elastomers can be stretched by a factor of 10 and yet completely recover to their original shape. Although their properties are quite different from thermosets, they have a similar molecular structure that is different from the thermoplastics. In popular nomenclature, thermoplas- tics and thermosets are known as plastics and elastomers are known as rubbers. Thermoplastics are commercially the most important of the three types, constituting around 70% of the tonnage of all synthetic polymers produced. Thermosets and elastomers share the remaining 30% about evenly. Common TP polymers include polyethylene, polyvinylchloride, polypropylene, polystyrene, and nylon.
- A.A. Collyer(Author)
- 2016(Publication Date)
- Elsevier Science(Publisher)
polymerization process. The molecules in a given plastic material are most unlikely to be Table 1.1: Comparison of the mechanical properties of several types of engineering materials [2-4] Material Specific gravity (gem 1 ) Modulus (GNm 2 ) Specific modulus (MNmkg 1 ) Strength (MNm 2 ) Specific strength (kNmkg 1 ) Aluminium Mild Steel Brass (70 C u / 3 0 Zn) Nylon 66 Polycarbonate Nylon 6 6 / 30% glass 2.7 7.86 8.5 1.14 1.24 1.38 71 210 100 3 2.3 8 26 27 12 2.6 1.9 5.8 80 460 550 80 60 160 30 59 65 70 48 116 2 Thermoplastics as Engineering Materials of exactly the same length and a molecular weight average, Mw, is generally quoted for a given grade. The molecular weight average has an important eflfect on the particular polymer: if Mw is very large the mechanical properties of the polymer will be enhanced but it will be difficult to process whereas, if Mw is low, there will be inferior mechanical properties, but good processing characteristics. A compromise is necessary here. In a plastic material the polymer chains can coil and uncoil, entangle and align. When a stress is applied to a polymer sample, the chains uncoil and align over a period of time (time-dependent properties) and, if the temperature is high enough, the molecules will slip over one another (flow). The above is true only of thermoplastic materials, which can be softened repeatedly by raising the temperature. Thermosetting materials start as thermoplastics but the first time they are heated crosslinks are formed. These give a three-dimensional network structure that is not broken down by further heating. Elastomers too behave like thermosets but are distinguished from them by their large capacity for extension. Further discussion will be limited to thermoplastics. In Figure 1.1, the lower curve shows how the elastic modulus of an amorphous thermoplastic material varies with temperature.
eBook - PDFEngineering Materials
Volume 3
- William Bolton(Author)
- 2014(Publication Date)
- Butterworth-Heinemann(Publisher)
6 Polymeric materials Objectives: At the end of this chapter you should be able to: Describe the basic structures of polymers. Explain how polymer crystal Unity affects polymer properties. Explain the significance of the glass transition temperature. Explain the effects of temperature and time on the properties of a polymer. Explain the effect of orientating polymer chains on the properties of the polymer. Explain how the properties of polymers may be modified by additives. Describe the benefits that can be obtained from copolymerisation. Describe the properties and applications of common thermoplastic and thermosetting polymers. Explain the characteristic structure of an elastomer and its mechan-ical properties. Describe the properties and applications of common elastomers. Describe the applications of polymer foams, polymer based sand-wich materials and polymer composites. POLYMERS The term polymer is used to indicate that a compound consists of many repeating structural units. The prefix 'poly' means many. Each structural unit in the compound is called a monomer. Thus the plastic polyethylene is a polymer which has as its monomer the sub-stance ethylene. For many plastics the monomer can be determined by deleting the prefix 'poly' from the name of the polymer. If you apply heat to a plastic washing-up bowl the material softens. Removal of the heat causes the material to harden again. Such a material is said to be thermoplastic. The term implies that the material becomes 'plastic' when heat is applied. If you applied heat to a plastic cup you might well find that the material did not soften but charred and decomposed. Such a material is said to be a thermosetting plastic. Another type of polymer is the elastomer. Rubber is an elastomer. An elastomer is a polymer which by its structure allows considerable extensions which are reversible.
eBook - PDFEngineering Chemistry
Fundamentals and Applications
- Shikha Agarwal(Author)
- 2019(Publication Date)
- Cambridge University Press(Publisher)
6.1 Introduction Polymers are compounds of very high molecular weights formed by the combination of a large number of small repeating units. The word ‘polymer’ is derived from the Greek word poly meaning ‘many’ and mer meaning ‘part’. The process by which the simple molecules (monomers) are converted into polymers is called polymerisation. For example, many ethylene molecules combine to form a giant molecule of polythene. n CH 2 CH 2 Polymerisation ( → 2 2 CH — CH ) n Ethylene Polythene (monomer) (polymer) where n = number of monomers in the polymeric chain. The number of repeating units in a polymeric chain is called ‘degree of polymerisation’. In the above example, ‘n’ is the degree of polymerisation. Polymers are also called macromolecules because of their big size. In fact, the terms polymers and macromolecules are often used synonymously. However, strictly speaking, a polymer contains repeating units (monomers), whereas a macromolecule is a giant molecule that may or may not contain monomer units. For example, chlorophyll and haemoglobin are macromolecules but not polymers. Polyethene may be regarded as a polymer as well as a macromolecule because it contains a large number of repeating units. Thus, all polymers are macromolecules and not vice versa. 6.2 Classification of Polymers Polymers may be classified in various manners. 1. On the basis of origin On the basis of origin, polymers are of two types: (a) Natural polymers (b) Synthetic polymers POLYMERS Chapter 6 Polymers 353 (a) Natural polymers They are polymers that occur in nature. For example, starch (polymer of a-D-glucose), cellulose (a polymer of b-D-glucose), proteins (polymer of a-amino acids) and natural rubber (a polymer of poly-cis-isoprene). (b) Synthetic polymer It is a polymer that is prepared artificially in the laboratory. For example, polyethylene (PE), polyvinylchloride (PVC), nylon, terylene, bakelite, synthetic rubber, etc.
eBook - PDF- Ahmet Gurses(Author)
- 2015(Publication Date)
- Jenny Stanford Publishing(Publisher)
Therefore, anionic polymerization is perfectly suitable for manufacturing parts directly from the monomer via casting, reaction injection molding (RIM), and rotational molding (Rijswijk, 2007; Tung, 1993). 1.3 Properties of Polymers 1.3.1 Mechanical Properties Polymers are macromolecules that vary from liquids and soft rubbers to hard and rigid solids (Meijer and Govaert, 2005). The unique properties of polymers coupled with their light weight make them preferable alternatives to metallic and ceramic materials in many applications. In the selection of a polymer for a specific use, its mechanical properties must be taken into account. The term “mechanical properties” is commonly used to denote stress–strain relationships for polymer systems. Unlike many more familiar materials where these relationships depend essentially only on temperature, in polymeric systems time dependence is also important (Aklonis, 1981). This is important, not only in those applications where the mechanical properties play a primary role, but also in other applications where other characteristics of the polymer, such as electrical, optical, or thermal properties, are crucial. In the latter cases, mechanical stability and durability of the polymer may be required for the part to perform its function satisfactorily. Properties of Polymers 60 Polymers and Polymer Synthesis The mechanical behavior of a polymer is a function of its microstructure or morphology. Polymer morphology itself depends on many structural and environmental factors. Compared with those of metals and ceramics, polymer properties show a much stronger dependence on temperature and time. This strong time and temperature sensitivity of polymer properties is a consequence of the viscoelastic nature of polymers. This implies that polymers exhibit a combined viscous and elastic behavior.
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