• Home
  • Textbooks
  • Materials Science and Engineering. An Introduction
  • Characteristics, Applications, and Processing of Polymers

Materials Science and Engineering. An Introduction

William D. Callister

Chapter 15

Characteristics, Applications, and Processing of Polymers - all with Video Answers

Educators

Chapter Questions

02:16

Problem 1

From the stress-strain data for poly(methyl methacrylate) shown in Figure 15.3, determine the modulus of elasticity and tensile strength at room temperature $\left[20^{\circ} \mathrm{C}\left(68^{\circ} \mathrm{F}\right)\right]$, and compare these values with those given in Table 15.1.
oelastic Deformation

Ameer Said
Ameer Said
Numerade Educator
00:37

Problem 2

In your own words, briefly describe the phenomenon of viscoelasticity.

Hunza Gilgit
Hunza Gilgit
Numerade Educator
01:20

Problem 3

For some viscoelastic polymers that are subjected to stress relaxation tests, the stress decays with time according to

$$
\sigma(t)=\sigma(0) \exp \left(-\frac{t}{\tau}\right)
$$

where $\sigma(t)$ and $\sigma(0)$ represent the timedependent and initial (i.e., time $=0$ ) stresses, respectively, and $t$ and $\tau$ denote elapsed time and the relaxation time; $\tau$ is a timeindependent constant characteristic of the material. A specimen of some viscoelastic polymer with the stress relaxation that obeys Equation 15.10 was suddenly pulled in tension to a measured strain of 0.5 ; the stress necessary to maintain this constant strain was measured as a function of time. Determine $E_r(10)$ for this material if the initial stress level was $3.5 \mathrm{MPa}(500 \mathrm{psi})$, which dropped to $0.5 \mathrm{MPa}(70 \mathrm{psi})$ after 30 s .

Manik Pulyani
Manik Pulyani
Numerade Educator
01:42

Problem 4

In Figure 15.27, the logarithm of $E_r(t)$ versus the logarithm of time is plotted for PMMA at a variety of temperatures. Make a plot of $\log E_r(10)$ versus temperature and then estimate its $T_g$.
(FIGURE CAN'T COPY)

Ameer Said
Ameer Said
Numerade Educator
02:48

Problem 5

On the basis of the curves in Figure 15.5, sketch schematic strain-time plots for the following polystyrene materials at the specified temperatures:
(a) Crystalline at $70^{\circ} \mathrm{C}$
(b) Amorphous at $180^{\circ} \mathrm{C}$
(c) Crosslinked at $180^{\circ} \mathrm{C}$
(d) Amorphous at $100^{\circ} \mathrm{C}$

Ameer Said
Ameer Said
Numerade Educator
02:48

Problem 5

On the basis of the curves in Figure 15.5, sketch schematic strain-time plots for the following polystyrene materials at the specified temperatures:
(a) Crystalline at $70^{\circ} \mathrm{C}$
(b) Amorphous at $180^{\circ} \mathrm{C}$
(c) Crosslinked at $180^{\circ} \mathrm{C}$
(d) Amorphous at $100^{\circ} \mathrm{C}$

Ameer Said
Ameer Said
Numerade Educator
01:57

Problem 6

(a) Contrast the manner in which stress relaxation and viscoelastic creep tests are conducted.
(b) For each of these tests, cite the experimental parameter of interest and how it is determined.

Ameer Said
Ameer Said
Numerade Educator
01:57

Problem 6

(a) Contrast the manner in which stress relaxation and viscoelastic creep tests are conducted.
(b) For each of these tests, cite the experimental parameter of interest and how it is determined.

Ameer Said
Ameer Said
Numerade Educator
04:38

Problem 7

Make two schematic plots of the logarithm of relaxation modulus versus temperature for an amorphous polymer (curve $C$ in Figure 15.8).
(a) On one of these plots demonstrate how the behavior changes with increasing molecular weight.
(b) On the other plot, indicate the change in behavior with increasing crosslinking.
cture of Polymers
cellaneous Mechanical Characteristics

Ameer Said
Ameer Said
Numerade Educator
01:37

Problem 8

For thermoplastic polymers, cite five factors that favor brittle fracture.

Narayan Hari
Narayan Hari
Numerade Educator
01:11

Problem 9

(a) Compare the fatigue limits for PMMA (Figure 15.11) and the steel alloy for which fatigue data are given in Problem 8.20.
(b) Compare the fatigue strengths at $10^6$ cycles for nylon 6 (Figure 15.11) and 2014-T6 aluminum (Figure 8.34).
ormation of Semicrystalline Polymers formation of Elastomers)

Ameer Said
Ameer Said
Numerade Educator
03:09

Problem 10

In your own words, describe the mechanisms by which semicrystalline polymers (a) elastically deform and (b) plastically deform, and (c) by which elastomers elastically deform.

Ameer Said
Ameer Said
Numerade Educator
03:19

Problem 11

Briefly explain how each of the following influences the tensile modulus of a semicrystalline polymer and why:
(a) Molecular weight
(b) Degree of crystallinity
(c) Deformation by drawing
(d) Annealing of an undeformed material
(f) Annealing of a drawn material

Ameer Said
Ameer Said
Numerade Educator
02:42

Problem 12

Briefly explain how each of the following influences the tensile or yield strength of a semicrystalline polymer and why:
(a) Molecular weight
(b) Degree of crystallinity
(c) Deformation by drawing
(d) Annealing of an undeformed material

Ameer Said
Ameer Said
Numerade Educator
00:50

Problem 13

Normal butane and isobutane have boiling temperatures of -0.5 and $-12.3^{\circ} \mathrm{C}$ (31.1 and $9.9^{\circ} \mathrm{F}$ ), respectively. Briefly explain this behavior on the basis of their molecular structures, as presented in Section 14.2.

Ameer Said
Ameer Said
Numerade Educator
02:05

Problem 14

The tensile strength and number-average molecular weight for two poly(methyl methacrylate) materials are as follows:
$$
\begin{array}{cc}
\hline \begin{array}{c}
\text { Tensile Strength } \\
(\text { MPa })
\end{array} & \begin{array}{c}
\text { Number-Average } \\
\text { Molecular Weight }(\mathrm{g} / \text { mol })
\end{array} \\
\hline 50 & 30,000 \\
150 & 50,000 \\
\hline
\end{array}
$$
Estimate the tensile strength at a numberaverage molecular weight of $40,000 \mathrm{~g} / \mathrm{mol}$.

Narayan Hari
Narayan Hari
Numerade Educator
01:28

Problem 15

The tensile strength and number-average molecular weight for two polyethylene materials are as follows:
$$
\begin{array}{cc}
\begin{array}{c}
\text { Tensile Strength } \\
\text { (MPa) }
\end{array} & \begin{array}{c}
\text { Number-Average } \\
\text { Molecular Weight }(\mathrm{g} / \text { mol })
\end{array} \\
\hline 90 & 20,000 \\
180 & 40,000 \\
\hline
\end{array}
$$
Estimate the number-average molecular weight that is required to give a tensile strength of 140 MPa .

Manik Pulyani
Manik Pulyani
Numerade Educator
04:20

Problem 16

For each of the following pairs of polymers, do the following: (1) state whether or not it is possible to decide whether one polymer has a higher tensile modulus than the other; (2) if this is possible, note which has the higher tensile modulus and then cite the reason(s) for your choice; and (3) if it is not possible to decide, then state why.
(a) Branched and atactic poly(vinyl chloride) with a weight-average molecular weight of $100,000 \mathrm{~g} / \mathrm{mol}$; linear and isotactic poly(vinyl chloride) having a weight-average molecular weight of $75,000 \mathrm{~g} / \mathrm{mol}$
(b) Random styrene-butadiene copolymer with $5 \%$ of possible sites crosslinked; block styrene-butadiene copolymer with $10 \%$ of possible sites crosslinked (c) Branched polyethylene with a numberaverage molecular weight of $100,000 \mathrm{~g} / \mathrm{mol}$; atactic polypropylene with a number-average molecular weight of $150,000 \mathrm{~g} / \mathrm{mol}$

Ameer Said
Ameer Said
Numerade Educator
05:09

Problem 17

For each of the following pairs of polymers, do the following: (1) state whether or not it is possible to decide whether one polymer has a higher tensile strength than the other; (2) if this is possible, note which has the higher tensile strength and then cite the reason(s) for your choice; and (3) if it is not possible to decide, then state why.
(a) Linear and isotactic poly(vinyl chloride) with a weight-average molecular weight of $100,000 \mathrm{~g} / \mathrm{mol}$; branched and atactic poly(vinyl chloride) having a weight-average molecular weight of $75,000 \mathrm{~g} / \mathrm{mol}$
(b) Graft acrylonitrile-butadiene copolymer with $10 \%$ of possible sites crosslinked; alternating acrylonitrile-butadiene copolymer with $5 \%$ of possible sites crosslinked
(c) Network polyester; lightly branched polytetrafluoroethylene

Ameer Said
Ameer Said
Numerade Educator
01:50

Problem 18

Would you expect the tensile strength of polychlorotrifluoroethylene to be greater than, the same as, or less than that of a polytetrafluoroethylene specimen having the same molecular weight and degree of crystallinity? Why?

Ameer Said
Ameer Said
Numerade Educator
01:45

Problem 19

For each of the following pairs of polymers, plot and label schematic stress-strain curves on the same graph (i.e., make separate plots for parts a, b, and c).
(a) Polyisoprene having a number-average molecular weight of $100,000 \mathrm{~g} / \mathrm{mol}$ and $10 \%$ of available sites crosslinked; polyisoprene having a number-average molecular weight of $100,000 \mathrm{~g} / \mathrm{mol}$ and $20 \%$ of available sites crosslinked
(b) Syndiotactic polypropylene having a weight-average molecular weight of 100,000 $\mathrm{g} / \mathrm{mol}$; atactic polypropylene having a weightaverage molecular weight of $75,000 \mathrm{~g} / \mathrm{mol}$
(c) Branched polyethylene having a numberaverage molecular weight of $90,000 \mathrm{~g} / \mathrm{mol}$; heavily crosslinked polyethylene having a number-average molecular weight of $90,000 \mathrm{~g} / \mathrm{mol}$

Manik Pulyani
Manik Pulyani
Numerade Educator
00:40

Problem 20

List the two molecular characteristics that are essential for elastomers.

Hunza Gilgit
Hunza Gilgit
Numerade Educator
04:01

Problem 21

Which of the following would you expect to be elastomers and which thermosetting polymers at room temperature? Justify each choice.
(a) Linear and highly crystalline polyethylene
(b) Phenol-formaldehyde
(c) Heavily crosslinked polyisoprene having a glass-transition temperature of $50^{\circ} \mathrm{C}$ $\left(122^{\circ} \mathrm{F}\right)$
(d) Lightly crosslinked polyisoprene having a glass-transition temperature of $-60^{\circ} \mathrm{C}$ $\left(-76^{\circ} \mathrm{F}\right)$
(e) Linear and partially amorphous poly(vinyl chloride)

Ameer Said
Ameer Said
Numerade Educator
04:04

Problem 22

Fifteen kilogram of polychloroprene is vulcanized with 5.2 kg sulfur. What fraction of the possible crosslink sites is bonded to sulfur crosslinks, assuming that, on the average, 5.5 sulfur atoms participate in each crosslink?

Ameer Said
Ameer Said
Numerade Educator
01:48

Problem 23

Compute the weight percent sulfur that must be added to completely crosslink an alternating acrylonitrile-butadiene copolymer, assuming that four sulfur atoms participate in each crosslink.

Narayan Hari
Narayan Hari
Numerade Educator
01:41

Problem 24

The vulcanization of polyisoprene is accomplished with sulfur atoms according to Equation 15.4. If $45.3 \mathrm{wt} \%$ sulfur is combined with polyisoprene, how many crosslinks will be associated with each isoprene repeat unit if it is assumed that, on the average, five sulfur atoms participate in each crosslink?

Narayan Hari
Narayan Hari
Numerade Educator
02:35

Problem 25

For the vulcanization of polyisoprene, compute the weight percent of sulfur that must be added to ensure that $10 \%$ of possible sites will be crosslinked; assume that, on the average, 3.5 sulfur atoms are associated with each crosslink.

Ameer Said
Ameer Said
Numerade Educator
01:57

Problem 26

Demonstrate, in a manner similar to Equation 15.4 , how vulcanization may occur in a chloroprene rubber.
ystallization

Narayan Hari
Narayan Hari
Numerade Educator
02:31

Problem 27

Determine values for the constants $n$ and $k$ (Equation 10.17) for the crystallization of polypropylene (Figure 15.17 ) at $150^{\circ} \mathrm{C}$.

Narayan Hari
Narayan Hari
Numerade Educator
01:01

Problem 28

Name the following polymer(s) that would be suitable for the fabrication of cups to contain hot coffee: polyethylene, polypropylene, poly(vinyl chloride), PET polyester, and polycarbonate. Why?

Hunza Gilgit
Hunza Gilgit
Numerade Educator
00:55

Problem 29

Of those polymers listed in Table 15.2, which polymer(s) would be best suited for use as ice cube trays? Why?

Hunza Gilgit
Hunza Gilgit
Numerade Educator
04:26

Problem 30

For each of the following pairs of polymers, plot and label schematic specific volume versus temperature curves on the same graph (i.e., make separate plots for parts a, b, and c).
(a) Linear polyethylene with a weightaverage molecular weight of $75,000 \mathrm{~g} / \mathrm{mol}$; branched polyethylene with a weightaverage molecular weight of $50,000 \mathrm{~g} / \mathrm{mol}$
(b) Spherulitic poly(vinyl chloride), of 50\% crystallinity, and having a degree of polymerization of 5000 ; spherulitic polypropylene, of $50 \%$ crystallinity, and degree of polymerization of 10,000
(c) Totally amorphous polystyrene having a degree of polymerization of 7000 ; totally amorphous polypropylene having a degree of polymerization of 7000

Ameer Said
Ameer Said
Numerade Educator
03:56

Problem 31

For each of the following pairs of polymers, do the following: (1) state whether or not it is possible to determine whether one polymer has a higher melting temperature than the other; (2) if it is possible, note which has the higher melting temperature and then cite reason(s) for your choice; and (3) if it is not possible to decide, then state why.
(a) Branched polyethylene having a numberaverage molecular weight of $850,000 \mathrm{~g} / \mathrm{mol}$; linear polyethylene having a number-average molecular weight of $850,000 \mathrm{~g} / \mathrm{mol}$
(b) Polytetrafluoroethylene having a density of $2.14 \mathrm{~g} / \mathrm{cm}^3$ and a weight-average molecular weight of $600,000 \mathrm{~g} / \mathrm{mol}$; PTFE having a density of $2.20 \mathrm{~g} / \mathrm{cm}^3$ and a weight-average molecular weight of $600,000 \mathrm{~g} / \mathrm{mol}$ (c) Linear and syndiotactic poly(vinyl chloride) having a number-average molecular weight of $500,000 \mathrm{~g} / \mathrm{mol}$; linear polyethylene having a number-average molecular weight of $225,000 \mathrm{~g} / \mathrm{mol}$
(d) Linear and syndiotactic polypropylene having a weight-average molecular weight of $500,000 \mathrm{~g} / \mathrm{mol}$; linear and atactic polypropylene having a weight-average molecular weight of $750,000 \mathrm{~g} / \mathrm{mol}$

Ameer Said
Ameer Said
Numerade Educator
01:45

Problem 32

Make a schematic plot showing how the modulus of elasticity of an amorphous polymer depends on the glass transition temperature. Assume that molecular weight is held constant.

Manik Pulyani
Manik Pulyani
Numerade Educator
00:53

Problem 33

Briefly explain the difference in molecular chemistry between silicone polymers and other polymeric materials.

Hunza Gilgit
Hunza Gilgit
Numerade Educator
00:55

Problem 34

List two important characteristics for polymers that are to be used in fiber applications.

Hunza Gilgit
Hunza Gilgit
Numerade Educator
01:08

Problem 35

Cite five important characteristics for polymers that are to be used in thin-film applications.
lymerization

Narayan Hari
Narayan Hari
Numerade Educator
01:20

Problem 36

Cite the primary differences between addition and condensation polymerization techniques.

Hunza Gilgit
Hunza Gilgit
Numerade Educator
05:07

Problem 37

(a) How much ethylene glycol must be added to 20.0 kg of terephthalic acid to produce a linear chain structure of poly(ethylene terephthalate) according to Equation 15.9?
(b) What is the mass of the resulting polymer?

Ameer Said
Ameer Said
Numerade Educator
01:27

Problem 38

Nylon 6,6 may be formed by means of a condensation polymerization reaction in which hexamethylene diamine $\left[\mathrm{NH}_2-\left(\mathrm{CH}_2\right)_6-\right.$ $\mathrm{NH}_2$ ] and adipic acid react with one another with the formation of water as a byproduct. What masses of hexamethylene diamine and adipic acid are necessary to yield 20 kg of completely linear nylon 6,6 ? (Note: the chemical equation for this reaction is the answer to Concept Check 15.12.)

Manik Pulyani
Manik Pulyani
Numerade Educator
00:53

Problem 39

What is the distinction between dye and pigment colorants?

Hunza Gilgit
Hunza Gilgit
Numerade Educator
01:57

Problem 40

Cite four factors that determine what fabrication technique is used to form polymeric materials.

Narayan Hari
Narayan Hari
Numerade Educator
01:06

Problem 41

Contrast compression, injection, and transfer molding techniques that are used to form plastic materials.

Hunza Gilgit
Hunza Gilgit
Numerade Educator
00:59

Problem 42

Why must fiber materials that are melt spun and then drawn be thermoplastic? Cite two reasons.

Hunza Gilgit
Hunza Gilgit
Numerade Educator
01:05

Problem 43

Which of the following polyethylene thin films would have the better mechanical characteristics: (1) formed by blowing, or (2) formed by extrusion and then rolled? Why?

Hunza Gilgit
Hunza Gilgit
Numerade Educator