- Author
-
Kashiwagi, T.
|
Hirata, T.
|
Brown, J. E.
- Title
- Thermal and Oxidative Degradation of Poly(methyl methacrylate): Molecular Weight.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
Forestry and Forest Products Research Inst., Tsukuba, Japan
- Journal
-
Macromolecules,
Vol. 18,
No. 2,
131-138,
February 1985
- Keywords
-
oxygen
|
polymethyl methacrylate
|
molecular weight
|
thermogravity
|
zip length
|
thermal degradation
- Abstract
- The mechanisms of thermal degradation and thermal oxidation of poly(methyl methacrylate) (PMMA) were studied by measuring the molecular weight of rapidly quenched samples thermally degraded in nitrogen and air in the range of temperatures between 200 and 325 Deg. C. Results show that thermal oxidation reduces the degree of polymerization much faster than does thermal degradation. Random scission is the initiation step for both thermal degradation and oxidative degradation. The activation energy for the random scission initiation is 233 kJ/mol for thermal degradation and 64 kJ/mol or oxidative degradation. The average zip length decreases from 2620 to 1340 with an increase in temperature from 258 to 324 Deg. C for thermal degradation. However, the average zip length increases from 20 to 102 with an increase in temperature from 205 to 251 Deg. C for thermal oxidative degradation. A reasonable value of activation energy for the termination reaction in nitrogen, 104 kJ/mol, is obtained only for the assumption of first-order termination.