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1、1,The Science and Engineering of Materials, 4th ed Donald R. Askeland Pradeep P. Phul,Chapter 15 - Polymers,2,Objectives of Chapter 15,Discuss the classification of Polymers Learn two main ways of creating a Polymer Study the effect of temperature on Thermoplastics Study mechanical properties of The
2、rmoplastics,3,Chapter Outline,15.1 Classification of Polymers 15.2 Addition Polymerization 15.3 Condensation Polymerization 15.4 Degree of Polymerization 15.5 Typical Thermoplastics 15.6 StructureProperty Relationships in Thermoplastics 15.7 Effect of Temperature on Thermoplastics,4,Chapter Outline
3、(Continued),15.8 Mechanical Properties of Thermoplastics 15.9 Elastomers (Rubbers) 15.10 Thermosetting Polymers 15.11 Adhesives 15.12 Additives for Plastics 15.13 Polymer Processing and Recycling,5,Section 15.1 Classification of Polymers,Linear polymer - Any polymer in which molecules are in the for
4、m of spaghetti-like chains. Thermoplastics - Linear or branched polymers in which chains of molecules are not interconnected to one another. Thermosetting polymers - Polymers that are heavily cross-linked to produce a strong three dimensional network structure. Elastomers - These are polymers (therm
5、oplastics or lightly cross-linked thermosets) that have an elastic deformation 200%.,6,2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.,Figure 15.1 Schematic showing linear and branched polymers. Note that branching can occur in any ty
6、pe of polymer (e.g., thermoplastics, thermosets, and elastomers). (a) Linear unbranched polymer: notice chains are not straight lines and not connected. Different polymer chains are shown using different shades and design to show clearly that each chain is not connected to another. (b) Linear branch
7、ed polymer: chains are not connected, however they have branches. (c) Thermoset polymer without branching: chains are connected to one another by covalent bonds but they do not have branches. Joining points are highlighted with solid circles, (d) Thermoset polymer that has branches and chains that a
8、re interconnected via covalent bonds. Different chains and branches are shown in different shades for better contrast. Places where chains are actually chemically bonded are shown with filled circles.,7,8,Table 15.1 Comparison of the three polymer categories,2003 Brooks/Cole, a division of Thomson L
9、earning, Inc. Thomson Learning is a trademark used herein under license.,2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.,2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.
10、,9,2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.,Figure 15.2 Three ways to represent the structure of polyethylene: (a) a solid three-dimensional model, (b) a three-dimensional “space” model, and (c) a simple two-dimensional model.,
11、10,2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.,Figure 15.3 Two ways to represent the benzene ring. In this case, the benzene ring is shown attached to a pair of carbon atoms, producing styrene.,11,Example 15.1 Design/Materials Sel
12、ection for Polymer Components,Design the type of polymer material you might select for the following applications: a surgeons glove, a beverage container and a pulley. Example 15.1 SOLUTION The glove must be capable of stretching a great deal in order to slip onto the surgeons hand. This requirement
13、 describes an elastomer. A thermoplastic such as polyethylene terephthalate (PET) will have the necessary formability and ductility needed for this application. A relatively strong, rigid, hard material is required to prevent wear, so a thermosetting polymer might be most appropriate.,12,Section 15.
14、2 Addition Polymerization,Addition polymerization - Process by which polymer chains are built up by adding monomers together without creating a byproduct. Unsaturated bond - The double- or even triple-covalent bond joining two atoms together in an organic molecule. Functionality - The number of site
15、s on a monomer at which polymerization can occur.,13,2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.,Figure 15.4 The addition reaction for producing polyethylene from ethylene molecules. The unsaturated double bond in the monomer is b
16、roken to produce active sites, which then attract additional repeat units to either end to produce a chain.,14,2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.,Figure 15.5 Initiation of a polyethylene chain by chain-growth may involve (a) producing free radicals from initiators such as benzoyl peroxide, (b) attachment of a polyethylene repeat unit to one of the initiator radicals
