12. Electron spin resonance of stable aromatic radical intermediates in pyrolysis

✍ Scribed by I.C. Lewis; L.S. Singer

• Publisher: Elsevier Science
• Year: 1968
• Tongue: English
• Weight: 148 KB
• Volume: 6
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(68)90315-1

✦ Synopsis

ABSTRACTS

above 650"HTT, and no resonance reappearing above that (checked up to 1600°C). The temperature dependence is for PVC exactly Curie type, so is also for the sugar chars, however, with a deviation gradually showing up above HTT of 700°C. It is believed that this deviation is due to increasing admixture of conduction carrier absorption. A-centers were made by oxidation under pressure on sugar heat treated from 800" to 1600' and PVC from 708" to f680", as well as on P33 carbon black heat treated from 1000" to 1600°C. A-centers on sugar and on PVC exhibit exactly Curie type behavior up to HTT 900°C. For chars heat treated to I loo"-16OO*C the ratio R = IL&r rapidly decreases to values in the range 2 -3-2.0. A-centers on P33 carbon black give R around 2.2-l *8. Samples of P33 with various concentrations of A-centers were prepared in order to study the mixing effect between the ESR of localised A-centers. Surprisingly it was found that the degree of deviation from Curie law does not depend on the concentration of A-centers.