ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
This paper is an account of some studies of the mechanism of degradation of an uncrosslinked polyurethan prepared from poly(propylene oxide) (PPO) and 2,4-tolylene diisocyanate (TDI) at temperatures up to 320°C in a vacuum or inert atmosphere. Fractionation of polymers before and after degradation provides information about the mechanism of degradation since the molecular weight distributions obtained are dependent on the mode and sites of bond scission. A recent publication describes the column elution method of fractionation developed for undergraded and slightly degraded PPG-TDI. PPO-TDI gives essentially most probable molecular weight distributions at an initial intrinsic viscosity [η] of ∼ 0.68 dl/g and also after degradation to [η] ∼ 0.24 dl/g. This invariancy of the distribution strongly suggests a randon scission process. Other types of degradation, e.g., free-radical unzipping initiated at the chain ends, could also give invariant most probable distributions. However, such depolymerizations would be accompanied by much larger extents of volatilization than were observed for these polymers (〈5% volatilization).
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760060107
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