Add time:08/24/2019         Source:sciencedirect.com

Resins prepared from 3,5-xylenol and formaldehyde in 1:1 and 2:3 molar ratios, catalysed by both sodium hydroxide and ammonia were carbonised to 1000°C, then heat-treated to temperatures ranging from 1500 to 2800°C. Crystallite sizes were measured from the broadening of X-ray powder diffraction lines. Whereas the sodium hydroxide catalysed resin carbons showed Lc increases from 10 Å at 1000°C to 30–45 Å at HTT = 2800°C, those from ammonia catalysed resins gave Lc increases from 20–30 Å at 1000°C to 200–320 Å at 2800°C. 1:1 resins gave larger crystallites than 2:3 resins. The results for 1:1 ammonia-catalysed resin accorded very well with published data. The degree of graphitisability of chars formed from 3,5-xylenol/formaldehyde resoles at 1:1 molar ratio was found to be strongly dependent on the initial hydroxyl ion concentration but otherwise independent of the nature of the catalyst. At very low [OH−](~ 10−7g ion/1), and at high [OH−](~ 10−1 g ion/1), the carbons were only feebly graphitising, while at intermediate [OH−](~ 10−3g ion/1), the degree of graphitisability was high. Values of Lc for resoles catalysed by nitrogen-containing alkalis showed that nitrogen had no appreciable effect on degree of graphitisability.

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