THE INFLUENCE OF THE MOLECULAR WEIGHTDISTRIBUTION OF NOVOLAC OLIGOMER ON THE CHARRESIDUE OF THE CURED PHENOLIC FORMALDEHYDERESIN

摘要

The phenolic resin had served as the binder for highly oxidation and ablative-resistantstructures. The molecular structure and the molecular weight distribution of the novolac oligomer hadgreat influence on the cross-linking structure and the char yield . In order to indicate the relation ofthe structure and the properties, in this paper, the molecular weight and its distribution were obtainedthrough the field-desorption mass spectrometry(FD-MS) method, which could provide absolutemolecular masses for each oligomeric species, from the 13C-NMR spectrum , the novolac oligomerwas detected to be composed of the ortho-ortho substituted structure, ortho-para substituted structure,para-para substituted structure. The chemical structures of the oligomer and their cured resins werealso modeled. As ablative resistant materials, the favorable molecular structures of the novolacoligomer are containing mainly trimer, tetramer and pentamer.