Although, several researches on synthesis and characterization of benzoxazines and
polybenzoxazines have appeared in the literature, detailed studies on thermal
characterization are still limited. In this study, polymerization and thermal
degradation mechanisms of benzoxazines were investigated via direct pyrolysis mass
spectrometry. Benzoxazine monomers prepared by reactions of phenol or bisphenol-
A with aniline or methyl amine were analyzed to investigate the effects of the
structures of phenyl and amine groups on both polymerization and thermal
degradation behaviours.
It has been proposed in the literature that polymerization of benzoxazines occurs by
ring opening polymerization of oxazine ring / cleavage of O-CH2 bond of the oxazine
ring and attack of n-CH2 group to phenol or bisphenol-A ring. However, the direct
pyrolysis mass spectrometry analyses of polymerization and thermal degradation of
benzoxazines pointed out that after the cleavage of O-CH2 bond of the oxazine ring,
polymerization proceeded through opposing pathways.
Strong evidences confirming coupling of (CH3)NCH2 or (C6H5)NCH2 groups
yielding dimers involving diamine linkages were detected. Polymerization of the
dimer by the reactions with the corresponding monomers was proposed. In case of
benzoxazines based on bisphenol-A, the results indicated polymerization of the dimer
ii
by coupling of both of the oxazine rings. On the other hand, polymerization of the
dimer through the ethylene units (vinyl polymerization) in case of benzoxazine
monomer based on phenol and methyl amine was also noted. For polybenzoxazines
based on aniline another polymerization pathway involved attack of radicals
generated by cleavage of the oxazine ring to aniline ring.
Multi-step thermal decomposition was observed for all the polybenzoxazines under
investigation confirming the presence of units with different structures and stabilities.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12610409/index.pdf |
| Date | 01 March 2009 |
| Creators | Bagherifam, Shahla |
| Contributors | Hacaloglu, Jale |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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