duongat_E54WK10

duongat_E54WK10 - Announcements Final Exam - Friday, March...

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Chapter 14 - 1 Announcements Final Exam - Friday, March 21, 10:30 - 12:30pm at DBH 1100 Review Session - Wednesday, March 19, 5:00 - 6:50pm at DBH 1100 Send us suggestions on what you would like for us to review Questions on specific problems and concepts will be accepted Will not accept questions in the form of “Will________ be on the final”
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Chapter 14 - 2 MOLECULAR WEIGHT molecules of # total polymer of wt total = ν Μ i i w i i n M w M M x M Σ = Σ = M w is more sensitive to higher molecular weights Molecular weight , M i : Mass of a mole of chains. Lower M higher M Adapted from Fig. 14.4, Callister 7e.
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Chapter 14 - 3 Molecular Weight Calculation - M n
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Chapter 14 - 4 Molecular Weight Calculation - M w
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Chapter 14 - 5 Degree of Polymerization, n n = number of repeat units per chain i i w i i w n i i n m f m m m M n w n m M n x n Σ = = = = = = υνιτ ρεπεατ οφ ϖειγητ μολεχυλαρ αωεραγε ϖηερε C C C C C C C C H H H H H H H H H H H H H H H H H C C C C H H H H H H H H H ( ) n i = 6 mol. wt of repeat unit i Chain fraction m = 28g/mol
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Chapter 14 - 6 Polymer Crystallinity Polymers rarely 100% crystalline Too difficult to get all those chains aligned % Crystallinity : % of material that is crystalline. -- TS and E often increase with % crystallinity. -- Annealing causes crystalline regions to grow. % crystallinity increases. Adapted from Fig. 14.11, Callister 6e. (Fig. 14.11 is from H.W. Hayden, W.G. Moffatt, and J. Wulff, The Structure and Properties of Materials , Vol. III, Mechanical Behavior , John Wiley and Sons, Inc., 1965.) crystalline region amorphous region
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Chapter 14 - 7 Homework problem hints 14.9, you are asked to calculate average chain length (L) and avg. end-to-end distance (r ) using equations that relate bond angle to bond length between chain atoms (d) - assume d = 0.154 14.24, you are asked to calculate the number of repeat units for unit cell given unit cell parameters. Once you calculate the volume, use equation 3.5 to relate the density to the given parameters.
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Chapter 14 - 8 Composites Combine materials with the objective of getting a more desirable combination of properties Ex: get flexibility & weight of a polymer plus the strength of a ceramic Principle of combined action Mixture gives “averaged” properties
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Chapter 14 - 9 Elastic modulus , E c , of composites: -- two approaches. Application to other properties: -- Electrical conductivity , σ e : Replace E in equations with σ e . -- Thermal conductivity , k : Replace E in equations with k . Adapted from Fig. 16.3, Callister 7e . (Fig. 16.3 is from R.H. Krock, ASTM Proc , Vol. 63, 1963.) Composite: Particle lower limit: 1 E c = V m E m + V p E p c m m upper limit: E = V E + V p E p “rule of mixtures” Data: Cu matrix w/tungsten particles 0 20 40 60 80 100 150 200 250 300 350 vol% tungsten E (GPa) (Cu) (W)
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Chapter 14 -10 Composite: Fiber Fibers very strong Provide significant strength improvement to
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duongat_E54WK10 - Announcements Final Exam - Friday, March...

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