Chapter 31, Problem 31.38P

Interpretation Introduction

(a)

Interpretation: An explanation for the differences observed in the $T_{\text{g}}$, and $T_{\text{m}}$ values for the given pair of polymers is to be stated.

Concept introduction: The glass transition temperature and the melt transition temperature are often used to characterize the behavior of a polymer on heating. They are denoted by $T_{\text{g}}$, and $T_{\text{m}}$ respectively. $T_{\text{g}}$ is the temperature at which hardness of an amorphous polymer decreases to become soft (not melted). $T_{\text{m}}$ is the temperature at which crystalline regions of polymer decreases to become amorphous.

Answer to Problem 31.38P

The given $T_{\text{g}}$, and $T_{\text{m}}$ values of polyester A is lesser than that of PET. It indicates the presence of more ordered crystalline regions and more disordered amorphous regions in PET than in polyester A.

Explanation of Solution

The given pair of polymers is,

Figure 1

The above polymer chains have both crystalline regions and amorphous regions. The ordered crystalline regions are called crystallites. Crystallites are the sections where polymer chain is bind together by intermolecular interactions. On the contrary amorphous regions are sections where polymer chains are randomly arranged. These sections are held together by weak intermolecular interactions.

A polymer containing high crystallites area possesses high $T_{\text{m}}$ value and a polymer chain containing high amorphous area possesses high $T_{\text{g}}$ value.

The given $T_{\text{g}}$, and $T_{\text{m}}$ values of polyester A is lesser than that of PET. Thus, it indicates the presence of more ordered crystalline regions and more disordered amorphous regions in PET than in polyester A.

Conclusion

The given $T_{\text{g}}$, and $T_{\text{m}}$ values of polyester A is lesser than that of PET. It indicates the presence of more ordered crystalline regions and more disordered amorphous regions in PET than in polyester A.

Interpretation Introduction

(b)

Interpretation: An explanation for the differences observed in the $T_{\text{g}}$, and $T_{\text{m}}$ values for the given pair of polymers is to be stated.

Concept introduction: The glass transition temperature and the melt transition temperature are often used to characterize the behavior of a polymer on heating. They are denoted by $T_{\text{g}}$, and $T_{\text{m}}$ respectively. $T_{\text{g}}$ is the temperature at which hardness of an amorphous polymer decreases to become soft (not melted). $T_{\text{m}}$ is the temperature at which crystalline regions of polymer decreases to become amorphous.

Answer to Problem 31.38P

The given $T_{\text{g}}$, and $T_{\text{m}}$ values of polyester A is lesser than that of nylon $6,6$. It indicates the presence of more ordered crystalline regions and more disordered amorphous regions in nylon $6,6$ than in polyester A.

Explanation of Solution

The given pair of polymers is,

Figure 2

The above polymer chains have both crystalline regions and amorphous regions. The ordered crystalline regions are called crystallites. Crystallites are the sections where polymer chain is bind together by intermolecular interactions. On the contrary amorphous regions are sections where polymer chains are randomly arranged. These sections are held together by weak intermolecular interactions.

A polymer containing high crystallites area possesses high $T_{\text{m}}$ value and a polymer chain containing high amorphous area possesses high $T_{\text{g}}$ value.

The given $T_{\text{g}}$, and $T_{\text{m}}$ values of polyester A is lesser than that of nylon $6,6$. Thus, it indicates the presence of more ordered crystalline regions and more disordered amorphous regions in nylon $6,6$ than in polyester A.

Conclusion

The given $T_{\text{g}}$, and $T_{\text{m}}$ values of polyester A is lesser than that of nylon $6,6$. It indicates the presence of more ordered crystalline regions and more disordered amorphous regions in nylon $6,6$ than in polyester A.

Interpretation Introduction

(c)

Interpretation: The comparison between the $T_{\text{m}}$ values for Kevlar and the $T_{\text{m}}$ value for nylon $6,6$ is to be stated.

Concept introduction: The glass transition temperature and the melt transition temperature are often used to characterize the behavior of a polymer on heating. They are denoted by $T_{\text{g}}$, and $T_{\text{m}}$ respectively. $T_{\text{g}}$ is the temperature at which hardness of polymer decrease to become soft (not melted). $T_{\text{m}}$ is the temperature at which crystalline regions of polymer decreases to become amorphous.

Answer to Problem 31.38P

The $T_{\text{m}}$ value for Kevlar is higher than nylon $6,6$.

Explanation of Solution

Kevlar is a polyamide, synthesized by $1,4$-diaminobenzene and terephthalic acid. It is light in weight but possesses high strength. It is due to the presence of aromatic rings as polymer backbone. This polymer backbone is much more symmetrical, and ordered than nylon $6,6$. It indicates the presence of more crystalline region in Kevlar than nylon $6,6$.

Figure 3

Since more ordered polymers have more $T_{\text{m}}$ values, it is expected that the $T_{\text{m}}$ value for Kevlar is higher than that of nylon $6,6$.

Conclusion

The $T_{\text{m}}$ value for Kevlar is higher than nylon $6,6$.