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Time–temperature–transformation cure diagrams of phenol–formaldehyde and lignin–phenol–formaldehyde novolac resins
Author(s) -
Pérez J. M.,
Rodríguez F.,
Alonso M. V.,
Oliet M.
Publication year - 2010
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.32866
Subject(s) - formaldehyde , glass transition , curing (chemistry) , differential scanning calorimetry , materials science , phenol formaldehyde resin , hexamethylenetetramine , phenol , lignin , polymer chemistry , composite material , isothermal process , chemical engineering , polymer , organic chemistry , chemistry , thermodynamics , engineering , physics
In this study, the time–temperature– transformation (TTT) cure diagrams of the curing processes of several novolac resins were determined. Each diagram corresponded to a mixture of commercial phenol–formaldehyde novolac, lignin–phenol–formaldehyde novolac, and methylolated lignin–phenol–formaldehyde novolac resins with hexamethylenetetramine as a curing agent. Thermomechanical analysis and differential scanning calorimetry techniques were applied to study the resin gelation and the kinetics of the curing process to obtain the isoconversional curves. The temperature at which the material gelled and vitrified [the glass‐transition temperature at the gel point ( gel T g )], the glass‐transition temperature of the uncured material (without crosslinking; T g 0 ), and the glass‐transition temperature with full crosslinking were also obtained. On the basis of the measured of conversion degree at gelation, the approximate glass‐transition temperature/conversion relationship, and the thermokinetic results of the curing process of the resins, TTT cure diagrams of the novolac samples were constructed. The TTT diagrams showed that the lignin–novolac and methylolated lignin–novolac resins presented lower T g 0 and gel T g values than the commercial resin. The TTT diagram is a suitable tool for understanding novolac resin behavior during the isothermal curing process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011