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Chap16_3pgs

# Chap16_3pgs - Polqlneffi 16-7 w Thc molecular eightof -3 is...

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Polqlneffi : 16-7 Thc molecular weight of polymcthyl mcthacrylate (see Table 16-3) is 250,000 g/mol. If all of the polymer chains arethe same length, calculate (a) the degree of polymerization and (b) the number of chains in I g of the polymer. Solution: The molecular weight of methyl methacrylate is: M W - 5 C + 2 C + 8 H : 1 0 0 g / m o l (a) Degree of polymerization : 250,000/100 : 2,500 (b) In I g of the polymer: = 2.408 X lOls chains 16-10 Analysis of a sample of polyacrylonitrile (PAN) (see Table 16-3) shows that there aresix lengths of chains, with the following number of chains of each length. Determine (a) the weight average molecular weight and degree of polymerization and (b) the number average molecular weight and degree of polymerization. Solution: Number of chains 10,000 18,000 17,000 15,000 9,000 4,000 73,000 - Mean Molecular weight of chains (g/mol) xi xiMi weight f, fiM, 0.137 411 30x106 0.044 132 0.247 1482 108 x 106 0.159 954 0.233 2097 153 x 106 0.226 2034 0.205 2460 180 x 106 0.265 3180 0.123 I 845 I 35 x 106 0. 199 2985 0.055 990 72 x 106 0.106 1908 9,285 678 x 106 I 1 , 1 9 3 3,000 6,000 9,000 12,000 15,000 18,000 SUilI = The molecular weight of the acrylonitrile monomer is: MWacryronitr.ite = 3 C + I N + 3 H = 53 g/mol (a) The weight average molecular weight and degree of polymerization are: MW* : 11,193 g/mol DP* : 11,193/53 : 2lI (b) The number average molecular weight and degreeof polymerization are: MWn : 9,285 g/mol DPn : 9285/53 g/mol - 175

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156 The Science and Engineering 0f Materials Instructor's Solutions Manual
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Chap16_3pgs - Polqlneffi 16-7 w Thc molecular eightof -3 is...

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