Thermally resistant carbazole-modified phenol-formaldehyde resins

摘要

Phenol-formaldehyde resins were modified with carbazole in order to improve their thermal resistance. Attempts to incorporate carbazole rings into novolac and resol resins were made using three methods: (1) the addition of N-(hydroxymethyl)carbazole (HMC) into a phenol-formaldehyde mixture, (2) the addition of carbazole into a phenol-hydroxymethyl derivative of acetone mixture, where the hydroxymethyl derivative of acetone was used as formaldehyde donor, and (3) by prolonging the time of high-temperature reaction between phenol, carbazole and formaldehyde. The temperature and time of reaction were critical for incorporation of carbazole, which successfully led to highly temperature-resistant carbazole-modified novolacs for the latter procedure. When carbazole was incorporated into novolac structure at a level of 8 mol%, the thermal resistance increased by 118 degrees C measured as 5% mass loss temperature. Other procedures led to solids containing carbazole or HMC as physical admixtures. The obtained composites revealed variable thermal resistance effects; the carbazole-modified resol containing 9 mol% of carbazole showed 47 degrees C increase of thermal resistance in comparison with non-modified resol, measured as 5% mass loss temperature. (c) 2015 Society of Chemical Industry