Lesson_3 Plastics and ceramics (6)

# Lesson_3 Plastics and ceramics (6) - 16-3 Degree of...

• Notes
• will.smith
• 3

This preview shows page 1 - 2 out of 3 pages.

where M i is again the mean molecular weight of each size range, but x i is the fraction of the total number of chains within each range. Either M x or M n can be used to calculate the degree of polymerization. The two following examples illustrate these concepts. EXAMPLE 16-4 Degree of Polymerization for 6,6-Nylon Calculate the degree of polymerization if 6,6-nylon has a molecular weight of 120,000 g/mol. SOLUTION The reaction by which 6,6-nylon is produced was described in Example 16-3. Hexamethylene diamine and adipic acid combine and release a molecule of water. When a long chain forms, there is, on an average, one water molecule released for each reacting molecule. The molecular weights are 116 g/mol for hexamethylene diamine, 146 g/mol for adipic acid, and 18 g/mol for water. The repeat unit for 6,6-nylon is: The molecular weight of the repeat unit is the sum of the molecular weights of the two monomers, minus that of the two water molecules that are evolved: M repeat unit ¼ 116 þ 146 ± 2 ð 18 Þ ¼ 226 g = mol Degree of polymerization ¼ 120 ; 000 226 ¼ 531 The degree of polymerization refers to the total number of repeat units in the chain. The chain contains 531 hexamethylene diamine and 531 adipic acid molecules. EXAMPLE 16-5 Number and Weight Average Molecular Weights We have a polyethylene sample containing 4000 chains with molecular weights

Subscribe to view the full document.

• Spring '14
• Colombo
• Physics, Polymer, Material Science, Plastics, Manufacturing, Metals, Molecular Weights

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern