Pyrolysis and structure of hyperbranched polyborate modified phenolic resins

Novel boron modified phenolic resins (PR) were prepared by blending PR with boric acid terminated hyperbranched polyborate (HBb). In order to reveal the effect of HBb on the structure of the carbonized PR, several experimental tools were employed such as X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Both the XRD and Raman spectroscopy analyses indicated that the boron incorporation resulted in an increase in the crystallite height and a decrease of interlayer spacing. Moreover, the C1s XPS of PR and HBb modified PR revealed that the graphite carbon decreased from 54.50% to 42.85% after incorporating boron atoms in that some of carbon atoms are substituted with boron atoms by forming B-C bonds. The presence of the B-C bonds indicated that part of boron atoms have been introduced into the structure of carbonized PR. These findings revealed that HBb exhibited obvious effects both in promoting the graphite crystallite and in improving the thermal stability.