# MSE 227_HW_3 _F10 ```MSE 227
Homework #3
Fall, 2010
Due: Sept. 21, 2010
1. Draw the mer, and calculate the mer weight for (a) poly vinyl chloride (b) polystyrene
and (c) polypropylene.
2. Explain, structurally, the difference between thermoplastic and thermosetting polymers.
3. Given the following data for polytetraflouroethylene, calculate the (a) number average
molecular weight, the (b) weight average molecular weight and (c) the degree of
polymerization.
Molecular Weight
1 – 5,000
5,000 – 20,000
20,000 – 35,000
35,000 – 50,000
50,000 – 65,000
65,000 – 80,000
80,000 – 100,000
Xi
0.02
0,13
0,21
0.30
0.19
0.11
0.04
Wi
0.015
0.14
0.19
0.32
0.175
0.09
0.07
4. Calculate the number of vacancies in a 1 cm3 block of iron at (a) room temperature and (b)
1000 oC if Qv = 0.85 eV.
5. Find (a) the number of lattice sites, N and (b) the activation energy Qv (use eV) for a
material that has nv = 5 x 107 at room temperature and nv = 1018 at 900 oC. (c) How many
vacancies does the material have at 600 oC?
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