Copolymers

9 Key excerpts on "Copolymers"

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  eBook - ePub

  Carraher's Polymer Chemistry

  • Charles E. Carraher Jr.(Author)
  • 2017(Publication Date)
  • CRC Press

    (Publisher)

  18 Polymer Technology Today, nearly 10,000 American companies are active in the general area of synthetic polymers. The following is a brief description of these companies divided according to their function:

  Manufacturers : There are over 200 major manufacturers of general-purpose polymers and numerous other manufacturers of specialty polymers.

  Processors : Some companies manufacture their own polymeric materials for subsequent processing, but the majority purchase the necessary polymeric materials from other companies. Processors may specialize in the use of selected polymers, such as nylons and polycarbonates, or focus on particular techniques of processing, such as coatings, films, sheets, laminates, and bulk-molded and reinforced plastics.

  Fabricators and finishers : The majority of companies are involved in the fabrication and finishing of polymers, that is, the production of the end products for industrial and general public consumption. Fabrication can be divided into three broad areas: machining, forming, and fashioning. Machining includes grinding, sawing, screwing, and other techniques. Forming includes molding and other methods of shaping and joining by welding, gluing, screwing, and other techniques. Fashioning includes cutting, sewing, sheeting, and sealing. Fabrication sequences vary depending on the polymeric material and desired end product.

  While much of the classic polymer technology was developed without the benefit of science, modern polymer technology and polymer science are closely associated. The technology of fibers, elastomers, coatings, composites, drug delivery, and plastics is discussed in this chapter.

  Chemistry is moving to the center stage in many areas of medicine, biology, engineering, environmental science, and physics. While solid-state physics is traditionally based on silicon, polymers offer a much wider vista of opportunities for application and fine-tuning those applications. Some areas are based on single crystals that may be small in our sight, but are large as compared to individual molecules. Even single silicon wafers with a minimum pattern dimension of 200 nm are on the order of 10 times the size of individual molecules. Eventually, electronic, photonic, and stress–strain behavior can be placed into single giant chains individually, creating chains that behave as entire assemblies behave today.

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  eBook - ePub

  Polymer Fillers and Stiffening Agents

  Applications and Non-traditional Alternatives

  • Chris Defonseka(Author)
  • 2020(Publication Date)
  • De Gruyter

    (Publisher)

  The word ‘plastics’ is derived from the Greek word ‘plastikos’. In general, a plastic can be defined as a material that is pliable and capable of being shaped by temperature and pressure. Plastics are based on polymers derived from the Greek word ‘polymeros’, with ‘poly’ meaning many, and meros meaning basic units. Polymers are also called resins in the commercial world, which is not really correct because resins are gum-like substances.

  Polymer chemistry is a multidisciplinary science that deals with chemical synthesis and chemical properties of polymers, which are considered to be macromolecules. Polymer chemists study the large complex molecules (polymers) that are built from smaller (sometimes repeating) units. They study how these smaller building blocks (monomers) were combined to create useful newer materials with specific characteristics. This is done by manipulating the molecular structure of the monomer/polymers used, the composition of the monomer/polymers combination, and applying chemical and processing technology that can, to a large extent, affect the properties of the final product. Polymer chemists are unique within the chemistry and scientific community because of their special knowledge and understanding of the relationships between polymer structures and their properties, spanning from the molecular to the macroscopic state.

  Although most polymer chemists work on applied research and development of polymers, there are opportunities for fundamental research (mainly in universities, government laboratories, and industrial labs) on theory of polymers in solid and liquid states, on the synthesis of new polymer structures, and also on the mechanical, electronic, optical, biological and other properties of those new polymers are supposed to have. Polymer chemistry and fundamental polymer research are inherently interdisciplinary, spanning chemistry, physics, engineering, economics and even biology.

  2.2  What are polymers?

  A polymer is a large molecule (macromolecule) composed of repeating basic structural units. These subunits are typically connected by covalent chemical bonds. Although the term ‘polymer’ generally refers to plastics, it encompasses a larger class of compounds, comprising natural and synthetic materials with a wide variety of properties. Because of the extraordinary range of polymeric materials, they have essential and vital roles in everyday life of people. They broadly range from the very familiar synthetic plastics and elastomers to natural biopolymers such as nucleic acids and proteins, which are essential for life.

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  eBook - ePub

  Handbook of Industrial Hydrocarbon Processes

  • James G. Speight(Author)
  • 2019(Publication Date)
  • Gulf Professional Publishing

    (Publisher)

  The synthesis of macromolecules composed of more than one monomeric repeating unit has been explored as a means of controlling the properties of the resulting material. In this respect, it is useful to distinguish several ways in which different monomeric units might be incorporated in a polymeric molecule. The examples presented (Table 14.3) refer to a two component system (A and B) in which the relationships of the monomers are varied. Most direct copolymerization processes of equimolar mixtures of different monomers give statistical Copolymers, if one monomer is much more reactive a nearly homopolymer of that monomer. Radical polymerization gives a statistical copolymer. In cases where the relative reactivity is different, the copolymer composition can sometimes be controlled by continuous introduction of a biased mixture of monomers into the reaction. A growing number of commercial polymers are actually composed of different types of unit attached together by chemical covalent bonds (Copolymers) and can comprise just two different units (binary Copolymers) or three different units (ternary Copolymers) and so on. This allows manipulation of the polymer properties to gain just the right combination of properties for a specific application. Monomers within a copolymer may be organized along the backbone in a variety of ways (Table 14.3): (i) alternating Copolymers possess regularly alternating monomer residues, (ii) periodic Copolymers have monomer residue types arranged in a repeating sequence, (iii) random Copolymers that have monomer residues arranged in no particular order, (iv) block Copolymers have two or more homopolymer subunits linked by covalent bonds, and (v) graft or grafted Copolymers that contain side chains that have a different composition or configuration than the main chain. Graft Copolymers are a special type of branched copolymer in which the side chains are structurally distinct from the main chain (Table 14.3)

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  Engineering Chemistry

  Fundamentals and Applications

  • Shikha Agarwal(Author)
  • 2019(Publication Date)
  • Cambridge University Press

    (Publisher)

  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. 2. On the basis of monomer composition (a) Homopolymer If a polymer consists of identical monomers, it is termed as homopolymer. nA Æ (A) n n CH 2 CH 2 → ( 2 2 CH — CH ) n ethylene polythene n CH 2 CHCl → ( 2 CH — CH ) n | Cl Vinyl chloride Polyvinyl chloride (b) Copolymer If a polymer is made up of more than one type of monomers it is called a copolymer. n A + m B A—A—B—B—A—B Depending on the arrangement of the monomeric units, the Copolymers may be fur- ther classified as (i) Random Copolymers The monomeric units are randomly arranged. A — B — B — A —B — A — A — B — B — A — B — — (ii) Alternating Copolymers The monomeric units are arranged in an alternating manner. A—B—A—B—A—B (iii) Block Copolymers The monomeric units are arranged in blocks. A—A—A—A—B—B—B—B (iv) Graft Copolymers They are branched Copolymers in which the backbone is formed of one type of monomer and the branches are formed of the other types of monomers. A—A—A—A—A—A—A–A B B B 354 Engineering Chemistry: Fundamentals and Applications 3. On the basis of chain structure (i) Linear polymer It has no branching other than the pendant groups associated with the monomer. Linear polymers are well packed and therefore have high densities. For example, polythene, nylons and polyesters. (ii) Branched polymers These are polymers in which the monomers are joined to form long chains with side chains or branches of different lengths. They are irregularly packed and have low densities. If the side chain is different from parent chain, they are called graft polymers.

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  Liquid Crystals, Laptops and Life

  • Michael R Fisch(Author)
  • 2004(Publication Date)
  • WSPC

    (Publisher)

  When we discuss polymers in more detail, you will see the role carbon plays in polymers. We will begin by discussing the basic chemistry of polymers. An impor- tant difference between polymers and materials such as fluids or metals is that polymers are long-chain or network type molecules. We will illustrate this using cartoons. We will then discuss the major types of polymers. From the materials viewpoint, there are two main types of polymers: ther- moplastic polymers that become less rigid when heated, and thermosetting polymers that become more rigid when heated. Both types of polymers are often used with additives that improve color, strength, and other physical and chemical properties. 9.3 What is a polymer? The term polymer literally means “many parts.” It is derived from Greek where poly means many and meros means unit or part; that is the simple, repeated building block of the chain or network. Thus, a polymer is a large molecule made up of many smaller and simpler chemical units covalently bonded together. For example, polyethylene (CH3-(CHz),-CH3) is a long chain molecule composed of ethylene molecules (CHz=CH2), Notice how- ever that the terminal groups are CH3. This is a fairly standard occurrence - the terminal moieties2 are frequently different from the central moieties that make up the polymer. Moreover, the two terminal groups need not be the same. Molecules with these general properties, that is, long chain molecules consisting of three different moities, a distinct one at each end and many repetitions of the central moiety, are ubiquitous. Such molecules occur in nature, and are also synthetically produced. This chapter will primarily focus on artificially produced polymers. Syn- thetic polymers often have a central structure of the form: -A-A-A-A-A-A-or -A-B-A-B-A-B-. –B—–B– .... ‘A plastic deformation is a permanent deformation that does not change upon re- ’A moiety is a sub-section of a molecule that has characteristic properties.

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  eBook - PDF

  The Fundamentals of Materials chemistry

  • 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).

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  Available until 4 Dec |Learn more

  Manufacturing Technology

  Materials, Processes, and Equipment

  • Helmi A. Youssef, Hassan A. El-Hofy, Mahmoud H. Ahmed(Authors)
  • 2011(Publication Date)
  • CRC Press

    (Publisher)

  339 13 Polymeric Materials and Their Processing 13.1 INTRODUCTION Polymers.are.molecular.materials.in.which.individual.molecules.or.units.are.chemically.bonded.in.a. chain-like.structure . .The.word. polymer .comes.from.the.Greek.roots. poly .(many).and. meros .(parts);. these.parts.are.known.as.monomers . .Monomers.are.made.up.of.organic.materials.in.which.atoms. of. carbon. are. joined. in. covalent. bonds. with. other. atoms. of. hydrogen,. oxygen,. nitrogen,. silicon,. chlorine,.fluorine,.or.sulfur . .Natural.polymers.such.as.silk,.shellac,.wood,.rubber,.and.cellulose.were. available.to.the.ancient.man . .However,.synthetic.or.semisynthetic.polymers,.manufactured.as.indus-trial.products,.are.recently.developed.materials . .The.term.“plastics”.is.a.general.common.name. given.to.most.synthetically.developed.polymers.that.may.contain.other.constituents.to.improve.per-formance.and/or.reduce.product.cost . .Again,.“plastic”.is.derived.from.the.Greek.. plastikos ,.which. means,. fit for molding. It.refers.to.the.malleability.or.plasticity.of.these.polymers.during.manufac-turing.that.allows.them.to.be.cast,.pressed,.or.extruded.into.a.variety.of.shapes,.such.as.films,.fibers,. plates,.tubes,.bottles,.boxes,.and.much.more . Polymeric.materials.in.the.form.of.plastics,.rubbers,.and.fibers.have.for.many.years.played.an. essential.role.in.everyday.life.as.electrical.insulators,.tires,.packaging.facilities,.food.and.beverage. containers,. textiles,. etc . . There. is. an. ever. increasing. demand. for. replacing. metallic. materials. in. machinery.and.equipment.with.plastics.for.improving.strength-to-weight.ratio,.safety.and.appear-ance,.and.for.noise.and.cost.reduction . .This.tremendous.development.of.polymeric.products.has. led.to.the.presently.accepted.reality.that.the.total.volume.of.produced.plastics.now.exceeds.that.of. metals,.and.the.rate.of.expansion.is.still.growing.faster .

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  eBook - PDF

  Fundamentals of Modern Manufacturing

  Materials, Processes, and Systems

  • Mikell P. Groover(Author)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  • On a volumetric basis, polymers are cost competitive with metals. • Plastics can be formed by molding into intricate part geometries, usually with no further process- ing required. They are very compatible with net shape processing. • On a volumetric basis, polymers generally require less energy to produce and process than metals, because the temperatures for working them are much lower than for metals. • Certain plastics are translucent and/or transparent, which makes them competitive with glass in some applications. • Polymers are widely used in composite materials (Chapter 9). On the negative side, polymers in general have the following limitations: (1) Strength is low relative to metals and ceramics; (2) modulus of elasticity or stiffness is also low—in the case of elastomers, of course, this may be a desirable characteristic; (3) service temperatures are limited to only a few hundred degrees because of the softening of thermoplastic polymers or degradation of thermosetting polymers and elastomers; (4) some polymers degrade when subjected to sunlight and other forms of radiation; and (5) plastics exhibit viscoelastic properties (Section 3.5), which can be a distinct limitation in load-bearing applications. This chapter examines the technology of polymeric materials. The first section provides an intro- ductory discussion of polymer science and technology. Subsequent sections survey the three basic categories of polymers: thermoplastics, thermosets, and elastomers. 8.1 Fundamentals of Polymer Science and Technology Polymers are synthesized by joining together many small molecules to form very large molecules, called macromolecules, that possess a chain-like structure. The small units, called monomers, are generally simple unsaturated organic molecules such as ethylene C 2 H 4 . The atoms in these mole- cules are held together by covalent bonds; and when joined to form the polymer, the same covalent bonding holds the links of the chain together.

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  eBook - PDF

  Engineering Chemistry

  Fundamentals and Applications

  • Shikha Agarwal(Author)
  • 2016(Publication Date)
  • Cambridge University Press

    (Publisher)

  For example, starch (polymer of a - D-glucose), cellulose (a polymer of b – D-glucose), proteins (polymer of a-amino acids), 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. 2. On the basis of monomer composition (a) Homopolymer If a polymer consists of identical monomers, it is termed as homopolymer. nA Æ (A) n n CH 2 CH 2 → ( 2 2 CH — CH ) n ethylene polythene n CH 2 CHCl → ( 2 CH — CH ) n | Cl Vinyl chloride Polyvinyl chloride (b) Copolymer If a polymer is made up of more than one type of monomers it is called a copolymer. n A + m B A—A—B—B—A—B Depending on the arrangement of the monomeric units, the Copolymers may be fur- ther classified as (i) Random Copolymers The monomeric units are randomly arranged. A — B — B — A —B — A — A — B — B — A — B — — (ii) Alternating Copolymers The monomeric units are arranged in an alternating manner. A—B—A—B—A—B (iii) Block Copolymers The monomeric units are arranged in blocks. A—A—A—A—B—B—B—B (iv) Graft Copolymers They are branched Copolymers in which the backbone is formed of one type of monomer and the branches are formed of the other types of monomers. A—A—A—A—A—A—A–A B B B Polymers 323 3. On the basis of chain structure (i) Linear polymer It has no branching other than the pendant groups associated with the monomer. Linear polymers are well packed and therefore have high densities. For example, polythene, nylons and polyesters. (ii) Branched polymers These are polymers in which the monomers are joined to form long chains with side chains or branches of different lengths. They are irregularly packed and have low densities. If the side chain is different from parent chain, they are called graft polymers.

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