Format:
iv, 26 Seiten
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Illustrationen
Series Statement:
Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 321
Content:
CONTENTS: Introduction. - Tensile strength apparatus. - Synthesis of linear polyurethane. - Tensile strength of polyurethane films. - Preparation of films and technique of measuring tensile strength. - Results. - Effect of N02 on polyurethane films. - Stiffness testers. - Static apparatus. - Experimental results. - Dynamic "stiffness" tester. - Summary. - Conclusion. - Literature cited. - Abstract.
Content:
A tensile strength, a static and a dynamic stiffness tester have been constructed for measuring appropriate mechanical properties of polymers as a function of temperature, environmental conditions (i.e. air plus NO2, O3, etc. or of the pollutants alone), exposure time and pollutant concentration. The apparatus were found to perform satisfactorily. The dynamic stiffness tester is particularly sensitive to the onset of cracking in polymeric materials due to ozone. The tensile strength of linear polyurethane was affected appreciably by NO2 alone and also by NO2 in presence of air. Chain scission cross-linking, evolution of CO2 and other small molecular weight compounds, and formation of nitro and nitroso groups along the polymer backbone are reactions underlying the observed changes in mechanical properties of the polymer. The static "stiffness" tester allows one to measure "stiffness" (Young's modulus) of polymers (especially elastomers) as a function of the above-mentioned parameters. A preliminary selection of polymeric skirting materials for SEV's can be made on the basis of results obtained as functions of temperature. Two industrial samples appeared to be suitable for this purpose on the basis of results obtained. "Stiffness" of these samples started to increase rapidly only at -40°C and -30°C whereas others became brittle at higher temperatures. The dynamic stiffness tester was tested with a natural rubber compound because of its susceptibility to ozone. Onset of cracking was accurately and clearly indicated by this instrument. An EPM compound proved quite resistant to ozone over prolonged periods of time. Time did not allow tests to be comipleted on all the compounds supplied by industry.
Note:
MAB0014.001: ZSP-202-321
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Online frei verfügbar
In:
Research report
Keywords:
Forschungsbericht
URL:
http://www.worldcat.org/oclc/227595043
