27.04.2016 Views

Callister - An introduction - 8th edition

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

564 • Chapter 14 / Polymer Structures<br />

14.7<br />

m ©f j m j<br />

For a copolymer, average repeat unit molecular<br />

weight<br />

551<br />

14.8 % crystallinity c 1 s a 2<br />

Percent crystallinity, by weight 554<br />

s 1 c a 2 100<br />

14.9<br />

¢P<br />

J P M<br />

¢x<br />

Diffusion flux for steady-state diffusion through<br />

a polymer membrane<br />

559<br />

List of Symbols<br />

Symbol<br />

f j<br />

m<br />

M i<br />

m j<br />

P<br />

P M<br />

x i<br />

x<br />

w i<br />

a<br />

c<br />

s<br />

Meaning<br />

Mole fraction of repeat unit j in a copolymer chain<br />

Repeat unit molecular weight<br />

Mean molecular weight within the size range i<br />

Molecular weight of repeat unit j in a copolymer chain<br />

Difference in gas pressure from one side of a polymer membrane to<br />

the other side<br />

Permeability coefficient for steady-state diffusion through a polymer<br />

membrane<br />

Fraction of the total number of molecular chains that lie within the<br />

size range i<br />

Thickness of polymer membrane across which diffusion is occurring<br />

Weight fraction of molecules that lie within the size range i<br />

Density of a totally amorphous polymer<br />

Density of a completely crystalline polymer<br />

Density of polymer specimen for which percent crystallinity is to be<br />

determined<br />

Processing/Structure/Properties/Performance Summary<br />

In the following diagram, we illustrate relationships among the various structural<br />

components for polymers, as discussed in this chapter (as well as Chapter 2), that<br />

influence the properties and processing of polymer fibers, as discussed in<br />

Chapter 15.<br />

Polymer chemistry<br />

Polymer Fibers<br />

(Structure)<br />

Electron<br />

configuration: C, H<br />

(Chapter 2)<br />

Covalent bonding<br />

(Chapter 2)<br />

van der Waals/<br />

hydrogen bonding<br />

(Chapter 2)<br />

Polymer molecules<br />

(Chapter 14)<br />

Molecular weight<br />

Molecular structure<br />

Molecular configuration<br />

Polymer crystallinity<br />

(semicrystallinity)<br />

(Chapter 14)<br />

Polymer crystals<br />

(spherulites)<br />

(Chapter 14)

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!