2010-03-24 Chapter 15 Polymer Applications and Processing

Chapter - Chapter 15 Structure/Properties Processing Applications of Polymers ISSUES TO ADDRESS What are the tensile properties of polymers and how

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Chapter 15 - 1 ISSUES TO ADDRESS. .. What are the tensile properties of polymers and how are they affected by basic microstructural features ? Hardening, anisotropy, and annealing in polymers . How does the elevated temperature mechanical response of polymers compare to ceramics and metals? Chapter 15: Structure/Properties, Processing & Applications of Polymers What are the primary polymer processing methods? What are common applications?
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Chapter 15 - 2 Thermoplastic and  Thermosetting Polymers Thermoplastic polymers  soften when heated (and eventually liquefy) and  harden when cooled. This process of liquefying and solidifying is reversible  and repeatable. These materials are normally fabricated by simultaneous  application of heat and pressure. e.g., Polyethylene(PE), Polypropylene(PP), Polycarbonate(PC),  Polymethylmethacrylate (PMMA), Acrylonitrile Butadiene Styrene(ABS), Polyamide  (PA, or nylon) PolyEthylene Terepthalate(PET), and PolyTetraFluroEthylene  (PTFE) Thermosetting polymers  become permanently hard when heat is applied  and do not soften upon subsequent heating.  During initial heat treatment,  covalent crosslinks are formed between adjacent molecular chains.   Thermoset polymers are generally harder, stronger, and more brittle than  thermoplastics, and have better dimensional stability. e.g., Epoxies, Phenol Formaldehyde (Bakelite),Urea Formaldehyde, Vinyl Esters,  and Unsaturated Polyesters (UPR) Important
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Chapter 15 - 3 Modified natural rubbers and synthetic rubbers are called elastomers. The process of crosslinking of elastomer chains is called vulcanization . Unvulcanized rubber is soft and has poor resistance to abrasion. Modulus of elasticity, tensile strength, resistance to degradation by oxidation are enhanced by vulcanization. 1 to 5 parts of sulphur (by weight) is added to 100 parts of rubber, in the vulcanization process. Elastomers Important
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Chapter 15 - 4 Types of Elastomers Elastomers – rubber Crosslinked materials Natural rubber Synthetic rubber and thermoplastic elastomers SBR- styrene-butadiene rubber styrene Silicone rubber butadiene
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Chapter 15 - 5 Mechanical Properties i.e. stress-strain behavior of polymers brittle polymer plastic elastomer σ FS of polymer ca. 10% that of metals Strains – deformations > 1000% possible (for metals, maximum strain ca. 10% or less) elastic modulus less than metal Adapted from Fig. 15.1, Callister 7e . Important
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Chapter 15 - 6 brittle failure plastic failure σ (MPa) ε x x crystalline regions slide fibrillar structure near failure crystalline regions align onset of necking Initial Near Failure semi- crystalline case aligned, cross- linked case networked case amorphous regions elongate unload/reload Stress-strain curves adapted from Fig. 15.1, Callister 7e. Inset figures along plastic response curve adapted from
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This note was uploaded on 09/30/2011 for the course PHYSICS 1410 taught by Professor Falco during the Spring '08 term at Texas State.

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Chapter - Chapter 15 Structure/Properties Processing Applications of Polymers ISSUES TO ADDRESS What are the tensile properties of polymers and how

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