A fundamental approach for the estimation of the mechanical glass transition temperature in gelatin.
The paper constitutes an attempt to overcome the empiricism prevalent in the estimation of the glass transition temperature (Tg) of gelatin networks using rheological techniques. In doing so, it presents a study of the viscoelastic properties of a well-characterised gelatin sample covering the structural properties from the rubbery region to the glassy state. The pattern of oscillatory behaviour on shear is given by a master curve produced by shifting data obtained at different temperatures along the logarithmic time scale. Data reduction does not hold for all temperatures thus giving rise to thermorheological complexity. Within the temperature range at which molecular processes are represented by a simple distribution of relaxation times, a fundamental argument is developed to pinpoint the mechanical Tg. This should improve confidence in measured glassy properties over the empirical indicators found in the literature. As a demonstration, the glass transition temperature of gelatin at "zero moisture" obtained using the proposed framework of analysis is contrasted with earlier attempts to identify the mechanical Tg of gelatin solids.
Kasapis
Stefan
S
Department of Chemistry, National University of Singapore, Block S3, Level 6, Science Drive 4, Singapore 117548, Singapore. chmsk@nus.edu.sg
Sablani
Shyam S
SS
D004548:Elasticity; D005780:Gelatin / Q000737:chemistry; D005898:Glass / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D019563:Mechanics; D009991:Oscillometry; D013696:Temperature; D013997:Time Factors; D044366:Transition Temperature; D014783:Viscosity; D014867:Water / Q000737:chemistry
D046911:Macromolecular Substances; D014867:Water; D005780:Gelatin