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Chapter 14: Problem 2

Compute repeat unit molecular weights for the following: (a) polytetrafluoroethylene (b) poly(methyl methacrylate) (c) nylon 6,6 (d) poly(ethylene terephthalate)

Short Answer

Expert verified
Answer: The repeat unit molecular weights for the given polymers are: (a) PTFE: 100.02 g/mol, (b) PMMA: 100.12 g/mol, (c) nylon 6,6: 226.32 g/mol, and (d) PET: 192.18 g/mol.

Step by step solution

01

Identify the repeat units

First, identify the repeat unit for each given polymer. This can be done by looking at the molecular structure of the polymer; the repeat unit is the smallest structure that repeats throughout the entire polymer chain. (a) PTFE repeat unit: -CF2- (b) PMMA repeat unit: -C(CH3)COOCH3- (c) Nylon 6,6 repeat unit: [-NH(CH2)6NHCO(CH2)4CO-] (d) PET repeat unit: [-OC(CH2)2COO(C6H4)COO-]
02

Calculate the molecular weight of the repeat units

Using the atomic weights of the elements from a periodic table, calculate the molecular weight of the repeat units for each polymer. The molecular weight of each repeat unit can be calculated by adding the atomic weights of all the atoms in the unit. (a) PTFE: 2 * (12.01 g/mol) + 4 * (19.00 g/mol) = 100.02 g/mol (b) PMMA: 5 * (12.01 g/mol) + 8 * (1.01 g/mol) + 2 * (16.00 g/mol) + (15.99 g/mol) = 100.12 g/mol (c) Nylon 6,6: 12 * (12.01 g/mol) + 22 * (1.01 g/mol) + 2 * (14.01 g/mol) + 4 * (16.00 g/mol) = 226.32 g/mol (d) PET: 10 * (12.01 g/mol) + 2 * (14.01 g/mol) + 8 * (16.00 g/mol) + 6 * (1.01 g/mol) + 8 * (1.01 g/mol) + 12 * (1.01 g/mol) = 192.18 g/mol
03

Write the final results

Finally, present the molecular weight of the repeat units for each polymer. Here are the repeat unit molecular weights for the four polymers: (a) PTFE: 100.02 g/mol (b) PMMA: 100.12 g/mol (c) Nylon 6,6: 226.32 g/mol (d) PET: 192.18 g/mol

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Most popular questions from this chapter

The density and associated percent crystallinity ( for two poly(ethylene terephthalate) materials are as follows: \begin{tabular}{lc} \hline\(\rho\left(\mathrm{g} / \mathrm{cm}^{3}\right)\) & crystallinity \((\%)\) \\\ \hline \(1.408\) & \(74.3\) \\ \hline \(1.343\) & \(31.2\) \\ \hline \end{tabular} (a) Compute the densities of totally crystalline and totally amorphous poly(ethylene terephthalate). (b) Determine the percent crystallinity of a specimen having a density of \(1.382 \mathrm{~g} / \mathrm{cm}^{3}\).

Sketch cis and trans structures for (a) polybuta( ) diene and (b) polychloroprene. Use two-dimensional schematics per footnote 12 of this chapter.

Crosslinked copolymers consisting of 35 wt \(\%\) (- ethylene and 65 wt \% propylene may have elastic properties similar to those for natural rubber. For a copolymer of this composition, determine the fraction of both repeat unit types.

Carbon dioxide diffuses through a high-density polyethylene (HDPE) sheet \(50 \mathrm{~mm}\) thick at a rate of \(2.2 \times 10^{-8}\left(\mathrm{~cm}^{3} \mathrm{STP}\right) / \mathrm{cm}^{2} \cdot \mathrm{s}\) at \(325 \mathrm{~K}\). The pressures of carbon dioxide at the two faces are \(4000 \mathrm{kPa}\) and \(2500 \mathrm{kPa}\), which are maintained constant. Assuming conditions of steady state, what is the permeability coefficient at \(325 \mathrm{~K}\) ?

Consider the diffusion of oxygen through a low(- density polyethylene (LDPE) sheet \(15 \mathrm{~mm}\) thick. The pressures of oxygen at the two faces are 2000 \(\mathrm{kPa}\) and \(150 \mathrm{kPa}\), which are maintained constant. Assuming conditions of steady state, what is the diffusion flux [in \(\left.\left(\mathrm{cm}^{3} \mathrm{STP}\right) / \mathrm{cm}^{2} \cdot \mathrm{s}\right]\) at \(298 \mathrm{~K}\) ?
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