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Studies on thermal behavior of imidazole diamine based benzoxazines
Author(s) -
Kannan Kesavan,
Krishnan Srinivasan,
Chavali Murthy,
Alagar Muthukaruppan
Publication year - 2018
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.46562
Subject(s) - diamine , imidazole , polymerization , materials science , polymer chemistry , thermal stability , thermosetting polymer , monomer , polymer , curing (chemistry) , organic chemistry , chemistry , composite material
The objective of the present work is to develop a novel type of structurally modified benzoxazines with improved performance characteristics using imidazole core based diamine with formaldehyde and different types of phenolic compounds in order to utilize them for high‐performance applications. In this work, an attempt has been made to bring down the polymerization temperature of the benzoxazine monomers, which is one of the most deficient factor restrict the applications of benzoxazines, when used in the form of adhesives, sealants, encapsulants, and matrices with other substrates, though they possess numerous advantages and valuable properties than those of other available thermosets. In this context, in this study, two approaches have been adopted to bring down the polymerization temperature, viz., (i) the development of structurally modified benzoxazine monomers with imidazole core and (ii) an incorporation of varying nature of chemical compounds as catalysts, to lower the polymerization temperature and to enhance the thermal stability and char yield. Three types of benzoxazines were developed using imidazole core based diamine with monohydric phenols and formaldehyde, at appropriate conditions. The molecular structure of benzoxazines was confirmed from Fourier transform infrared spectroscopy and 1 H‐nuclear magnetic resonance analysis. From data, it was observed that the imidazole diamine based benzoxazines prepared from 1‐naphthol exhibits lower curing temperature of about 192 °C than that of other samples studied in this work. In addition, the influencing effect of catalysts viz., 4‐hydroxy acetophenone, 4‐hydroxy benzaldehyde, 4‐hydroxyphenyl maleimide, and thiodipropionic acid (TPA) on thermal properties of benzoxazines also was studied. Among the catalysts, it was found that the TPA is the most efficient catalyst. In the case of imidazole diamine based benzoxazines prepared from cyanophenol, the TPA reduces value of polymerization temperature ( T p ) from 217 to 167 °C. The thermogravimetric analysis indicates that thermal stability of the benzoxazines are improved to a significant extent when 10 wt % catalysts were incorporated into the system. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 46562.