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:
There are essentially two ways to arrive at high softening polymers: crystallization and cross linking. The first approach leads to thermoplastic materials which have a more or less sharp and reversible melting point; the second produces three dimensional unmeltable networks which are thermosetting and can support very high temperatures without degradation. Factors which affect the mechanical behavior of a polymer exposed to high temperatures are degradation and cross linking. The first process is caused by scission of the chain molecules. The second process, cross linking, ties individual polymer chains into a rigid network, increases the molecular weight and leads to a very hard, brittle product which can neither be melted nor dissolved. The stability of a polymer against oxidation is always improved by the addition of an oxygen scavenger which reacts with oxygen in preference to the polymer and also by the addition of a UV absorber.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760050321
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