The Open UniversitySkip to content
 
Skip My preferences

My preferences

Skip Learning ToolsSkip Rate and Review

Rate and Review

Unit rating: 4.5 stars.
Rated by 3 user(s)
Skip Alternative FormatsSkip Tags

Tags

Please log in to tag your favourite units
Skip Share this unit with a friend

Share this unit with a friend

Help with sending a link to this unit (new window)
Permalink to this unit:
 

Topic outline

 

  • Time: 20 hours
    Level: Masters

 
 

Introduction

  • Introduction Resource
  • Polymers are materials composed of long molecular chains that are well-accepted for a wide variety of applications. This unit explores these materials in terms of their chemical composition, associated...
 

1 Polymer materials

  • The growth of poymers Resource
  • Polymers, or materials composed of long molecular chains, are now well-accepted for a wide variety of applications, both structural and non-structural, and for mass-manufactured as well as one-off speciality...
  • 1.1 Polymer types Resource
  • Traditionally, the industry has produced two main types of synthetic polymer – plastics and rubbers (Figure 3). The distinction is that plastics are, by and large, rigid materials at service temperatures...
  • 1.2 Product design and manufacture Resource
  • So what are the reasons for the continued growth in the use of polymers as shown in Figure 1? It cannot be raw material cost, since the source of synthetic polymers is crude oil or natural gas, prices...
 

2 Molecular engineering

  • Understanding the polymer state Resource
  • It was the pioneering scientific work of Hermann Staudinger in the early part of the twentieth century which led to an understanding of the polymer state at an atomic and molecular level. Until then, plastics...
  • 2.1 Chain repeat units Resource
  • The repeat units of a range of polymers together with the monomer units from which they are derived are shown in Table 3. The simplest repeat unit is that for polyethylene, and consists of two carbon atoms...
  • 2.2 Chain configuration Resource
  • The structure of repeat units is fixed by the chemical bonds between adjacent atoms. The shape or shapes thus created is known as the configuration, and for chains will be the chain configuration. Like...
  • 2.3 Chain conformations Resource
  • The repeat units or chains shown in the previous figures are all static representations of real chains and they are therefore of limited use. The key idea we need to explore real chains, and their influence...
  • 2.4 Structure-property relationships Resource
  • Given the large number of possible configurations in polymers, what guides to likely properties are available? We have already seen some of the effects on properties of changing tacticity, for example,...
  • 2.5 Molecular mass distribution Resource
  • In Figure 28 the peak (Mp) is at about 40 000. Number average () and weight average () molecular masses fall below and above the peak value. Determined using high temperature GPC
  • 2.6 Commercial polymers Resource
  • The increasing control of polymer structure by fine-tuned catalysis of polymerization opened up an enormous area for commercial exploitation, and new polymers are still being produced in this way (such...
 

3 Manufacture of monomers

  • Primary sources of synthetic polymers Resource
  • The most important primary sources of synthetic polymers are crude oil, natural gas and, to a minor extent, coal. Because all are primarily fuels rather than sources of materials, the manufacture of polymers...
  • 3.1 Petrochemical processing Resource
  • Following distillation of petroleum into the major fractions (gasoline C5 up to 95 °C, naphtha 75–175 °C, kerosine 175–225 °C), the naphtha cut is subjected to cracking to yield smaller, double bonded...
  • 3.2 Petrochemical intermediates and monomers Resource
  • About 80 per cent of all petrochemicals end up in polymers, the most important building blocks being ethylene, propylene, butadiene and benzene. The first three can be polymerized directly but an important...
  • 3.3 The petrochemical industry Resource
  • The four-fold increase in the price of oil in 1973–4, together with associated political events, proved a powerful stimulus in the development and exploitation of North Sea crude oil. Increasing the price...
 

4 Polymerization

  • Understanding the polymerization process Resource
  • Converting monomer to long chain polymer is the final step in the polymer manufacturing sequence. Polymerization is usually highly favourable in thermodynamic terms, mainly on energetic grounds because...
  • 4.1 Chain and step growth Resource
  • There are two basic ways of making chains. The first is to activate a small number of monomer units M which then successively consume other monomers. This mechanism is known as chain growth and is shown...
  • 4.2 Chain growth polymerization Resource
  • Chain growth polymerization is basically a three-stage process, involving initiation of active molecules, their propagation and termination of the active chain ends.
  • 4.3 Step growth polymerization Resource
  • In contrast to chain growth reactions, where high molecular mass polymers are formed almost from the start of the reaction, a stepwise reaction results in the molecular mass of the polymer increasing slowly...
  • 4.4 Copolymerization Resource
  • The alloying of metals to improve their properties is widespread and although many polymers used today are relatively pure (e.g. polystyrene, nylon), an increasing number are mixtures of two or more polymers....
  • 4.5 Polymer grades Resource
  • Polymers synthesised by a variety of routes are available in many grades from the large polymer manufacturing companies. Naturally enough, the grades of bulk tonnage polymers, such as LDPE, PVC, HDPE and...
 

5 Physical properties of polymers

  • The behaviour of polymers Resource
  • The manufacture of polymer products is controlled by two often conflicting demands: the quality of the finished article in terms of its response to its environment and the ease or difficulty of processing...
  • 5.1 Viscoelasticity of polymers Resource
  • The simplest models for the deformation behaviour of an ideal material are those of Hookean linear elasticity in the solid state, and Newtonian linear viscosity in the liquid state. The end point of elastic...
  • 5.2 Viscoelasticity and master curves Resource
  • An immediate consequence of the viscoelasticity of polymers is that their deformations under stress are time dependent. If the imposed mechanical stress is held constant then the resultant strain will...
  • 5.3 Dynamic mechanical properties Resource
  • Viscoelasticity is not experienced just under quasi-static conditions, i.e. when the imposed stresses and strains are constant or change only slowly. Polymers, and particularly rubbers, are often deliberately...
  • 5.4 Orientation in polymers Resource
  • Viscoelasticity, like thermodynamics, is concerned with the correlation of controllable variables and bulk, macroscopic phenomena. But one unique feature of polymeric materials is that the molecular unit,...
  • 5.5 Crystallisation of polymers Resource
  • The major benefits of crystallisation of chain molecules to end users are:
 

6 Design in polymers

  • A fresh approach? Resource
  • Polymeric materials offer substantial benefits over conventional materials in terms of their low density, relative freedom from corrosion, transparency or translucency, and a range of physical properties...
  • 6.1 Manufacturing and process methods Resource
  • Different production routes entail significantly different costings, and the selection of the manufacturing method is therefore a key step in the development of a product. For example a simple closed box...
  • 6.2 Materials selection Resource
  • Good design fulfils the product specification under the required service conditions as well as contributing to the cost effectiveness of its manufacture and maintenance. The product specification itself...
  • 6.3 Case history: the Topper boat Resource
  • Replacement of one polymeric material by another may be undertaken entirely for manufacturing reasons, and this is what happened in the redesign of the Topper dinghy for thermoplastic polymer. The dinghy...
  • 6.4 Market experience Resource
  • It is some 20 years since the Topper project was conceived by Peter Bean, Technical Director of Rolinx and Ian Proctor, the designer of the original GRP boat. Sales initially were excellent, especially...
 

7 Summary

  • 7 Summary Resource
  • Polymers are long chain molecules with properties dominated by their chain behaviour and the nature of their chemical make-up or constitution. The distinction between thermoplastics and thermosets has...
 

References and Acknowledgements

Skip Log inSkip Related educational resources