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Physico‐thermal Stabilities of Dye Solids I—Heat Capacities of some Disperse and Vat Dyes
Author(s) -
FLORES L.,
JONES F.
Publication year - 1971
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1971.tb03030.x
Subject(s) - sublimation (psychology) , differential scanning calorimetry , heat capacity , thermodynamics , materials science , thermal , disperse dye , void (composites) , solid state , chemical engineering , chemistry , composite material , dyeing , psychology , physics , engineering , psychotherapist
The application of differential scanning calorimetry to a number of pure disperse and vat dye solids to determine their molar heat capacities and to study the changes in this property with temperature is described. The method is used to detect possible solid‐state transitions occurring in the dyes on heating. Premonitory positive deviations from linearity are observed with three disperse dyes at temperatures up to 30 deg C below transition or melting points. The results are discussed in terms of Frenkel and Schottky disorder, and the activation energy of this disorder is calculated. For the three vat dyes examined, the heat capacity passes through a maximum on heating. The subsequent decrease in heat capacity is possibly due to an increase in lattice order caused by localised sublimation in void spaces within the crystals.